Minimally Invasive Surgery

Minimally invasive surgery (MIS) includes surgical techniques that are designed to minimize the invasiveness of the anatomic approach while maintaining or improving surgical precision and efficiency. Endoscopic surgery (endosurgery) involves performing a minimally invasive surgical procedure with visualization provided by an endoscope. Laparoscopic and thoracoscopic surgery include endoscopic approaches to the abdominal and thoracic cavities, respectively. The purpose of this chapter is to introduce the fundamentals of endosurgery to surgeons untrained in these techniques and to encourage the adept surgeon to do more.

Advantages and Disadvantages

Every veterinary surgeon is charged to restore biologic form and function. Of equal importance is the veterinary surgeon’s management of pain associated with the procedure. Advantages of the endosurgical techniques include reduced incision size, decreased closure times, minimal scar formation, and improved visualization of the surgical site. Evidence of a more rapid return to work and better cosmetic appearance in human patients does not necessarily apply to veterinary patients although attempts to compare postoperative activity levels of animals undergoing minimally invasive surgery have demonstrated that dogs undergoing laparoscopic ovariectomy with minimally invasive techniques recover more quickly than those undergoing open surgery.¹ The improved visualization provided by MIS is dramatic and is an invaluable teaching tool. Although moderate cost savings have been demonstrated when endosurgery is chosen in human medicine, the same issues do not apply to veterinary medicine. In fact, the initial investment for equipment purchase is considerable and the extra supplies needed for each case add to the cost of each procedure. These disadvantages, along with the greater learning curve, with its associated complications, often deter veterinarians from attempting MIS procedures. So why should veterinary surgeons consider endosurgical methods as an alternative, let alone a principal choice? The veterinary surgeon’s innate hunger for precision and technical skill may be enough to answer this question. Minimally invasive surgery is a state of mind–a creed. Furthermore, as the pioneer endosurgeon Nadeau pointed out in 1925, “How often is not the surgeon or the diagnostician confronted with a case in which the difficulties of reaching a decision urge the desire to get a glimpse of the body interior!”² Still more important is the issue of pain management. The surgical entry wound with endosurgery is considerably smaller than with traditional surgical approaches. A surgical entry wound often causes greater associated morbidity and pain than the internal operation itself. The simple reduction in entry wound size of endosurgery has led to reduced postoperative pain, reduced requirements for narcotic analgesics, fewer respiratory difficulties, reduced adhesion formation, earlier ambulation and return to feeding, and rapid return to self-sufficiency. The veterinary surgeon should investigate all means of pain management for their patients.

Indications and Contraindications

If the surgeon is proficient in performing minimally invasive surgery, endosurgery is simply an alternative approach to a surgical problem. The indication for a specific surgical procedure is no different from an open approach, except that with MIS there may be less postoperative pain, faster recovery time, and decreased wound infection rates and adhesion formation. The reduction in postoperative morbidity and enhanced visualization obtained with endosurgery may be relatively greater for animals with a very thick body wall. The primary contraindication for endosurgery is the anticipated failure to provide an adequate optical cavity. Significant adhesions, thoracic or abdominal effusion, or very large space-occupying masses are relative contraindications for an endoscopic approach. The presence of a diaphragmatic hernia is another relative contraindication. If a defect is present in the diaphragm, pneumothorax or pneumomediastinum may develop when abdominal insufflation is used to establish an optical cavity.

Safety and Efficacy

The veterinary surgeon should have a thorough understanding of each specific surgical therapeutic technique, including associated complications and contraindications. Those same complications and contraindications also apply to the endosurgical approach. Because the number of possible endosurgical procedures is almost endless, no purpose exists in listing all associated complications here. However, a few complications are specific to endosurgical approaches. Although the incidence of these complications is extremely low, some may be lethal and understanding such complications is mandatory. Client consent should be obtained for procedure conversion and the animal should always be surgically prepared for conversion to an open technique.

The anesthesiologist or anesthetist should be prepared for the unique aspect of anesthesia in the endosurgical patient. Several complications are associated with patient positioning and the use of insufflation gases in laparoscopy. Trendelenburg positioning (head-down tilt) and pneumoperitoneum (abdominal gas insufflation) increases the risks of gastrointestinal reflux and acid aspiration. Proper fasting, endotracheal intubation with a cuffed tube, and prompt attention to reflux are necessary. Abdominal distension produced by gas insufflation used in laparoscopy can trigger vasovagal reflexes, decrease venous return and cardiac output leading to hypotension. With compression of the diaphragm, there can be ventilation-perfusion mismatch and decreased vital capacity, functional residual capacity, and compliance. Positioning (head-up or head-down) contributes to this cardiopulmonary insult. Ventilatory support is mandatory in most cases. Thoracoscopic techniques provide additional challenges to the anesthesiologist in providing proper anesthesia and ventilation while establishing a working space within the thorax. In most cases, the space is established by decreasing the tidal volume of both lungs or by ventilating only one lung without insufflation of the thorax. An intimate knowledge of one-lung ventilation techniques is necessary for advanced thoracoscopic techniques. Anesthetic considerations for endosurgery are reviewed in the literature.³

Troubleshooting

Equipment failure that cannot be resolved during MIS will dictate conversion of the procedure to an open approach. Since veterinarians are generally directly responsible for hospital equipment and maintenance, a review of common equipment disorders is presented. An interruption or incompatibility of any one of these components will cause procedural delay. Hospital personnel need to be trained to set up, trouble-shoot, and solve issues efficiently. If inadequate light is encountered, the surgeon should ensure that the system has been white balanced prior to use, that the light source is taken off stand-by, and that the light guide cables are of sufficient diameter and compatible with the light source. A 5 mm scope will deliver less light than a 10 mm scope. In general, a smaller laparoscope needs to be positioned closer to a structure for the image to appear as bright as when using a larger scope from further away. When the camera image fails to appear on the monitor, it is usually caused by incorrect output to input connections. The output of the camera should be connected to the input of the monitor. If a video recorder is used, it is typically inserted between the output of the camera and the input of the monitor to ensure that the highest quality image is recorded.

Gas insufflation is used during endosurgery to create a viewing cavity, or to lift the body wall, thereby producing a protective distance between the viscera and instruments being inserted into the cavity. Automatic insufflators are used to regulate the body cavity gas pressure to a pre-set value, usually 8 to 15 mm Hg. When pressures exceed 20 to 25 mm Hg, there can be significant cardiopulmonary embarrassment. Carbon dioxide is the most commonly used gas for insufflation because it is cheap, it is most soluble (perhaps reducing the likelihood of gas embolus), it is rapidly resorbed and eliminated by the lungs, and it does not support combustion when electrocautery is used. However, CO₂ may cause irritation to the body cavity through formation of carbonic acid on visceral surfaces and is absorbed into the blood, possibly leading to hypercarbia, stimulation of the sympathetic nervous system, vasodilation, hypertension, tachycardia and other arrhythmias. Surgeons should try to use the lowest pressure that enables sufficient visualization. If inadequate insufflation of the abdominal cavity occurs, the gas supply to the insufflator, the pressure and flow settings on the insufflator, and tubing attachment at the trocar and at the insufflator should be checked. Further, all trocars should be examined for open stopcocks or inadequate seals.

The surgeon must be attentive to the introduction and position of their surgical instruments within body cavities at all times. Each instrument should be monitored by camera as it is introduced into the body cavity and followed to the target organ, keeping the tip of the instrument centered on the monitor. The surgeon should never coagulate or cut unless clear visualization of the target tissue is obtained. Most injuries to viscera (spleen, stomach, bowel, ureters, and lung) are due to blind placement of insufflation needles and trocars. Splenic injuries caused by Veress needle placement are usually self-limiting. Large vessel injury can occur as well, causing severe bleeding, or worse, venous air embolism through entrainment of insufflation gases. Diagnosis and treatment of air embolism requires cooperation between the surgeon and anesthesiologist. Monitoring for a precipitous drop in end-tidal CO₂ can be invaluable in these cases.
 

Equipment Needed
Light, Optics, Video: The multicomponent surgical video system

The standard video tower has a light source, light guide cable, rigid operating telescope, video camera, one or two video monitors, and often, a video recorder. For laparoscopy, a high-flow insufflator, CO₂ tank, yoke for the gas supply, and tubing are also used. The purpose of the system is to provide live, full color images of the interior of the body, as well as capture and storage of images for review.

General Considerations

Image quality is the foremost consideration. The video system component with the lowest resolution capabilities defines the resolution for the entire system. The final image is affected by a number of variables, including camera design, signal format, video processor, monitor capabilities, and user settings. The controls should be easy to identify and activate, providing easily interpretable feedback. Some degree of automation will further simplify use. Compatibility with existing equipment and hospital sterilization methods is important. Prior experience with the manufacturer is also invaluable.

Light Source

Purpose: Supplies light to surgical site via the endoscope.

Recommendations: Xenon or advance LED lamp with a minimum 500 hour lamp life and backup lamp. Lamp standby mode and bulb-life meter. Auto-illumination.

Explanation: Adequate illumination of the endosurgical field is essential to safely completing the procedure. Light transmitted from the tip of the endoscope must reflect off anatomic structures and be picked up by the lens system of the endoscope. Light emitted into the body cavity reduces in intensity by the square of the distance traveled. Changing focal points changes reflected light intensity. Such changes demand an adjustable or automatic light source output control. Automatic brightness control helps maintain a constant image brightness regardless of the target distance. Usually xenon, or more recently advanced LED light sources, are used over halogen or metal halide bulbs. Although these modern external light sources may operate at very high temperatures, little of this heat ever reaches the patient. However, if a xenon light source is used, burns and fires induced by excessive heat production at the interface between the fiberoptic light cable and the rigid operating endoscope are still quite possible. For this reason, the light source should not be left turned on when the fiberoptic cable is detached from the rigid operating endoscope. Auto-illumination, low-intensity default settings and lamp standby mode can help minimize this risk.

Fiberoptic Light Cable

Purpose: Carries light to surgical endoscope.

Recommendations: Secure connections and connector compat- ibility with multiple manufacturers (universal clamp). Adequate size, durable and flexible construction.

Explanation: The development of fiberoptics in the 1960s made it possible to present intense light to the endosurgical field without burning the patient. An incoherent bundle of glass fibers, 10 to 25 μm in diameter, connects the light source to the rigid surgical endoscope. Fiberoptic bundles fan around the inner core lens system of the endoscope, carrying light to the surgical field. Due to air-to-glass interface at connecting points and fiber mismatching, only approximately one-quarter of the original light is transmitted, making bright light sources necessary. Secure connections are necessary to prevent cable disconnections and burns. Durable, flexible construction is necessary to limit light fiber fracture and subsequent loss of delivered light.

Surgical Endoscope (Laparoscope)

Purpose: Directs light into surgical site and directs reflected light back to camera head.

Recommendations: Hopkins rod-lens system. Autoclave compatible. Compatible with all common light sources, light cables and video processors.

Explanation: Reflected light, incident with the operating endoscope, is captured by a lens system. The diameter of the standard lens system ranges from 1 to 5.5 mm, with the large lens providing better resolution. Laparoscopes vary in their depth of focus, magnification, color differentiation, brightness and resolution, as well as their angle of vision and field of view. Superior light capture is accomplished with the now common- place Hopkins glass rod-lens system, and high quality lens systems. Laparoscopes also vary in their sensitivity to reuse and sterilization methods.

Video Camera

Purpose: Generates an electrical signal from reflected light captured

Recommendations: Three-CCD (3-chip) cameras will generally provide superior image quality and color differentiation. Auto- white balance. Camera zoom control. Camera head with integrated, easy to use, imaging controls. Universal optical coupler will attach to a variety of surgical endoscopes.

Explanation: Light captured by the rigid operating endoscope can be viewed directly or with greater ease and resolution using a miniature video camera, also called a charge-coupled device (CCD). The CCD or “chip” is a photosensitive silicone sensor composed of thousands of photoelectric picture elements (pixels). Quality cameras use from one to three CCD chips. A single chip camera uses color-filter overlays or rotating filter wheels to produce color separation. Three chip cameras use a prism to separate the incoming light into the additive primary colors of red, blue and green (RBG), with each chip dedicated to one color, thus producing superior color reproduction. However, light sensitivity is more important than color separation. A high-quality single-chip camera can outperform some three-chip systems. Still–in general–three chip systems offer better color reproduction and image quality than single chip systems. The camera head can also have controls for light source control, image zoom and peripherals like a video recorder.

Camera resolution is based on the number of pixels available (called the “native resolution”) and is generally less than that of the video processor. Resolution is compromised in cameras with less than 400 horizontal rows of pixels. One-chip cameras typically generate signals with a maximum of 400 to 500 lines of horizontal resolution, whereas three-chip cameras can create signals with 700 or more. The camera is often the limiting factor for the overall resolution.

An optical coupler is used to attach the camera to a surgical endoscope. Video endoscopes have the camera situated at the tip of endoscope (so-called chip-on-the-tip configuration), but are less commonly used for laparoscopic surgery at this time.

Video Processor (Camera Control Unit or CCU)

Purpose: Translates the signal from the camera head into video signal and routes the video signal to the video monitor.

Recommendations: Variety of video format outputs (composite, S-video, RBG). Digital output for high definition systems (DVI). Matching outputs to display and camera inputs. Brightness and color controls.

Explanation: The overall resolution is affected by the method of communicating the image. The standard one-wire, composite video signal is simple and familiar. Component video signals (two-wire Y/C or S-video, and three-wire RBG) reproduce more monochrome and color image detail. High definition (HD) systems are becoming standardized at this time. To be considered HD, the system should have a 16:9 picture aspect ratio and either 720 horizontal progressive scan lines (720p), 1080 horizontal interlaced scan lines (1080i) or 1080 horizontal progressive scan lines (1080p) digital output formats. Progressive scan shows fewer artifacts with rapid movement, but interlaced is equally effective in laparoscopy. Since video processors cannot provide greater resolution than offered by the video camera, the CCD pixel arrays will also have to be larger or the resolution will not improve. The video processor will need to be paired with a flat-panel liquid crystal display (LCD) with a similar aspect ratio, horizontal lines and input formats. The monitor resolution should reflect the resolution of the camera or image quality may be lost. In general, the field is rapidly moving towards HD systems at this time.

Video Monitor

Purpose: Displays the live image

Recommendations: HD flat-panel LCD with a number of video format inputs (composite, S-video, RBG, and DVI). Consider using more than one LCD for alternate viewing. Horizontal lines of resolution or pixel density, as well as video inputs to match video processor outputs.

Explanation: A flat panel LCD will be necessary for HD video processor output. However, flat panel screens are also lightweight and easy to mount even when used with a lower resolution input. Flat-panel screens of various types have essentially replaced the traditional cathode ray tube monitor.

The US standard, NTSC (National Television System Committee) format has 525 horizontal scan lines, 4:3 picture aspect ratio and runs 30 fields or frames per second (fps). Many surgical monitors in use today have at least 550 to 700 horizontal lines of resolution, a 13-inch diagonal screen, and are medical grade to limit chassis electrical current leakage. However, the introduction of flat-panel fixed-pixel array monitors has changed the game. The resolution of these flat-panel monitors is determined simply by the physical number of columns and rows of pixels creating the display. The monitor must be compatible with the method of communicating the image from the camera (composite, S-video, RBG or digital), but then uses a digital video processor with memory array, called a scaling engine, to match the incoming image format. Again, the image resolution will be no better than the input from the camera regardless of the flat panel pixel density. The digital signal can be communicated through a standard Bayonet Neill-Concelman (BNC) connector using serial digital interface (SDI) or high-definition serial digital interface (HD-SDI). However, the industry has moved to digital communication via Digital Visual Interface (DVI). DVI is also compatible with High-Definition Multimedia Interface (HDMI) with no signal loss using DVI-to-HDMI adapter.

Video Image Capture

Purpose: Document and archive procedures, teaching

Recommendations: Large hard-drive with DVD archiving and input/output for additional storage attachment (eg. Universal Serial Bus - USB). Digital capture device for instantaneous and continuous capture. Capture resolution should match image resolution for equivalent replay (with alternative setting available).

Explanation: Picture archiving and communication systems (PACS) are computer-based systems that can store and retrieve images in digital format from several different diagnostic imaging modalities including endoscopic surgery. Digital-image storage does help organize storage of large volumes of images (such as radiographs) and video, however communication with a PACS is likely unnecessary for the average endosurgeon. Temporary storage to a large hard-drive and subsequent download to a DVD for storage will usually suffice, with the understanding that the average DVD lifespan is limited by the quality of the materials and manufacturing methods, as well as the storage and handling.

However, in general, manufacturers performing non-standardized accelerated age testing claim life spans ranging from 30 to 100 years for high quality DVD-R and DVD+R discs and up to 30 years for DVD-RW, DVD+RW and DVD-RAM. Alternatively, additional portable hard-drives may be connected to the primary hard-drive for archive download (if connectivity provided). HD image capture will require larger storage space.

Trends and the Future

Natural orifice “scarless” surgery is being evaluated for surgical access to organs deep inside the body, without external incisions in the abdominal wall. Operating room automation systems designed to control multiple operating-room devices using a single, common interface are available. Three-dimensional endoscopic surgical techniques have developed more slowly with concerns regarding surgeon’s perception of depth and scaling. Telepresence including telemedical training and telerobotic endoscopic surgery are well established. Telerobotic systems like the da Vinci robotic surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) are being used in more and more human community hospitals with more and more surgery going “robotic”. Small, wireless robots about 3 inches in length have been developed which when inserted into a body cavity can be controlled wirelessly by the physician to perform biopsy, drug delivery, and control of hemorrhage.

Endosurgical Instrumentation

Basic veterinary endosurgical hand-held instrumentation has not changed dramatically since it was introduced in the late 1990s. Endoscopic clip appliers, surgical staplers, and automatic suturing devices were introduced between 1990 and 2000 and are continuing to be refined for use in human surgery. Endoscopic clips have greatly facilitated endosurgical procedures and provide secure hemostasis and sealing of viscus structures. Multiple clip appliers enable rapid and repeated application of clips. These clips are used to occlude blood vessels and other small, hollow structures. They are useful in controlling acute bleeding; however, secure ligation is only accomplished with complete skeletonization of the vessel. Endosurgical stapling devices place six rows of linear staples that provide closure and hemostasis, and incision between the middle rows of staples. Staple leg length varies according to anticipated tissue thickness. Newer staplers have staggered staple heights with the outer rows forming larger staples and the inner rows forming smaller tighter staples. Cartridges are available in 30, 45, and 60 mm lengths.

Although monopolar and bipolar electrocautery have been used extensively in MIS, recent major advances have been made in methods for achieving hemostasis and cutting of tissue. The Harmonic Scalpel uses ultrasonic energy to coagulate and cut tissue, reducing lateral thermal injury and has an advantage because no electrical current passes through the patient’s body. The vibrating blade creates cavitation in the tissue which opens up planes of dissection that are not initially apparent. Dissection is facilitated by appropriate tissue tension. Water vapor generated during coagulation must be vented to ensure a clear surgical field. The LIGASURE bipolar sealing device, like the Harmonic Scalpel, can be used for dissection without precise skeletonization of vessels. The tissue to be coagulated and cut is grasped in the jaws of the instrument and current is applied while the tissue impedance is monitored by the instrument. When current flow drops below threshold, an audible alarm sounds to signal complete hemostasis and an internal knife can then be activated to cut the tissue. The LIGASURE is capable of effectively ligating vessels up to 7 mm in diameter. The Ethicon ENSEAL device also uses bipolar energy to simultaneously cut and seal tissue up to 7 mm in diameter. A unique polymer temperature control feature is provided within the jaws of the device to precisely heat tissue to 100 C and limit the lateral thermal spread outside the electrode area. Care should be taken to close the device prior to withdrawal from the trocar to prevent damage to insulation of the wires to the electrodes. The insulation of all monopolar devices should be inspected to ensure that it is intact, as burns may occur where a defect in insulation contacts tissues.

Endoscopic Suturing

The cost of materials for endoscopic suturing is less than for clips, staplers, and energy devices, but manual suturing is more time-consuming. A description of all aspects of laparoscopic suturing is beyond the scope of this chapter and the reader is referred to recent publications^4,5 and the following illustrations of extracorporeal ligation with Roeder knot, ligation with a pre-tied loop ligature, such as ENDOLOOP, and classic intracorporeal instrument knot tying.

Extracorporeal Knot Tying

Equipment

• Pretied endoknot or long suture (endosuture) (at least 48 cm)
• Knot Pusher
• One endoscopic needleholder and one endoscopic grasping forceps
• Endoscopic scissors

Technique

This technique is defined as throws created outside of the body under direct vision which are then transferred to the body cavity by a knot pusher. This technique, unlike the pre-tied loop ligature, can be used on skeletonized structures, and does not require a free end. The structure to be ligated is identified and isolated. The free end of a 48 cm suture is grasped with a needle driver and passed into the body cavity through a cannula. The ligature is passed around the structure with assistance of a second grasping forceps entering the body from another port. The ligature is then transferred to the original needle driver and pulled out through the cannula. The remainder of the ligature is fed into the cannula while the surgeon simultaneously pulls the free end of the ligature from the body cavity. The grasping forceps is used to prevent pulling and sawing to the tissue being ligated. The free ends of the ligature are tied in a Roeder knot (Figure 7-1A-F). The knot is then transferred to the body cavity with a knot pusher.
 

Pre-tied Loop (ENDOLOOP) Ligatures

Equipment

• Pretied loop ligature (ENDOLOOP or SURGITIE)
• One endoscopic needleholder and one endoscopic grasping forceps
• Endoscopic scissors

Technique

Pretied loop ligatures are commercially available as ENDOLOOP or SURGITIE ligatures and require a free pedicle for proper use. The pre-tied loop ligature is passed through one port and a grasping forceps is passed through a second port. The grasper is passed through the loop to grasp and elevate the structure to be ligated. The knot is placed at the level of the intended ligation, and the loop is slowly closed with a knot pusher. The commercially available products have a nylon cannula with a conical tip that serves as the knot pusher. The cannula is scored near a red tab. After the grasper is positioned through the loop the tab is broken from the cannula at the score point. The tab is held with one hand while the cannula is advanced with the other. (Figures 7-2A-F) Endoscopic scissors are used to cut the suture tail (Figures 7-2G-I).
 

Intracorporeal Instrument Knot Tying

Equipment

• Short ligature (10 to 15 cm) with a curved or half-curved (ski) needle
• Two endoscopic needleholders or one needleholder and one grasping forceps
• Endoscopic scissors

Technique

Endoscopic knot tying is an advanced technique that requires practice in an endoscopic training box for the surgeon to become proficient before attempting to perform the technqique on a patient. Proper suture placement requires proper trocarcannula placement. The surgeon places two working cannulas and one cannula for the laparoscope. Ideally, the cannulas will be positioned in baseball diamond configuration with the laparoscope positioned at home plate, pointing towards the monitor. The two working ports are positioned at first and third base, with the incision at second base. The incision should be oriented nearly parallel to the shaft of the active needle holder. One simple intracorporeal suture technique is illustrated in (Figure 7-3A-H).
 

Intracorporeal Suturing

Equipment

• ENDOSTITCH Suturing Device with ENDOSTITCH suture material available in sizes 0 to 4-0 (absorbable, silk, nylon, and polyester) 
• 10 mm trocar

Technique

The suture material is swaged to the center of a needle, oriented in a T-fashion. Each end of the needle is loaded into the jaws of the ENDOSTITCH suturing device. The needle can be toggled from one jaw to the other by flipping a switch on the suturing device handle. The needle is loaded on one side, the jaws of the device are closed on tissue, and the switch is flipped to transfer the needle to the other jaw of the instrument. Thus, the needle is held securely and passed through tissue easily, without the difficulty of loading the needle into the needle holder each time. After the tissue is apposed, it is possible to tie a knot by passing the needle around the suture material to create a loop and then passing the needle through the loop. Alternatively, barbed sutures, such as the V-LOC suture (Covidien) or STRATAFIX (Ethicon) can be utilized to avoid the need to tie an intracorporeal knot.

Laparoscopic Endosurgical Procedures

Patient Positioning

Equipment

• Tilt table or other means of tilting the animal by elevating the head or feet and rotating the animal side to side

Technique

The animal may be placed in several different positions, depending on the procedure. In general, the laparoscope should be inserted to face the monitor with the target tissue placed between the trocar insertion site and the monitor. Usually, the target tissue will be elevated for optimal visualization. For procedures involving the cranial abdomen or thorax, position the monitor at the head of the table and elevate the head. For procedures involving the caudal abdomen or thorax, position the monitor at the foot of the table and elevate the tail. For ovariectomy procedures, the animal will need to be rotated to the right and to the left to identify the left and right ovaries, respectively.

Access

Equipment

• Veress needle or Hasson trocar (blunt trocar with olive plug)

Technique

There are two methods used to create access to the abdominal cavity. A closed approach uses a Veress needle to insufflate CO₂ to create a space for primary trocar insertion. The body wall is grasped and lifted while the Veress needle is passed in the direction predicted to be devoid of viscera. Proper needle placement is confirmed by aspiration and hanging-drop techniques. The body cavity is insufflated with gas, and the needle is removed. The skin incision is made roughly equal to the diameter of the trocar being inserted, and the primary sharp trocar is then blindly placed in a similar fashion to the needle. In the dog, when the Veress needle is inserted at the umbilicus, it is not uncommon to injure the spleen. For this reason, many veterinarians use the open approach to gain entry to the abdominal cavity. The open approach, also known as the Hasson technique, uses a blunt trocar with an olive plug or a screw tipped trocar inserted under direct visualization. The skin incision is made and a midline incision is made through the linea alba. Sutures are placed on each side of the fascia and, after the trocar is inserted, are tied to the olive plug of the trocar (Figure 7-4A-F). Optical trocars, such as the OPTIVIEW, have a central channel for the laparoscope that allows continuous visualization of each tissue layer during insertion. They are used both with and without insufflation of the abdominal cavity. After the primary port is inserted, insufflation of the abdominal cavity with CO₂ is performed to provide a viewing cavity in which to work. Additional ports are placed as needed for each procedure.
 

Laparoscopic Liver, Intestinal and Pancreatic Biopsy Procedures

Indications

If abdominal exploratory and organ biopsy can be obtained with MIS, this method is preferred over other techniques. Laparoscopic liver biopsy enables the surgeon to obtain more tissue that is needed for heavy metal analysis than what can be obtained with ultrasound directed fine needle aspirates or ultrasound guided core biopsy procedures. Full thickness intestinal biopsy is preferred over obtaining endoscopic biopsy samples for accurate diagnosis of diseases of the intestinal tract. Finally, laparoscopy permits examination of internal organs and visual confirmation of hemostasis without the invasiveness of open surgery.

Equipment

• 5 mm trocars
• 5 mm blunt probe
• 5 mm endoscopic grasping forceps
• 5 mm endoscopic cup biopsy forceps
• Hemostatic agent such as ENDO-AVITENE, SURGICEL, GELFOAM, or collagen sponge
• Introducer sleeve and plastic push rod from a pre-tied loop ligature system (SURGITIE)

Technique

Liver Biopsy. When laparoscopic liver biopsy is the only technique being performed, positioning the animal in left lateral recumbency allows more of the liver surface to be exposed through the right lateral mid-abdominal approach. In addition, this position improves visualization because the falciform ligament moves out of the field. However, performing laparoscopic exploration is more difficult, so animals are usually positioned in dorsal recumbency if both techniques are to be performed.

If ascites is present, the open technique for primary port placement should be used to allow suctioning of the ascitic fluid before port placement. Pneumoperitoneum is created, the laparoscope is inserted, and the abdomen is inspected. The liver is inspected and any lesions are identified. A second 5 mm port is then placed in the right or left cranial abdominal quadrant, corresponding to the site of the lesion. A blunt probe is used to palpate and elevate each of the liver lobes prior to biopsy. Any remaining ascitic fluid is aspirated.

Liver biopsy is usually associated with minimal bleeding; however, placing small sections of Gelfoam into the abdominal cavity near the anticipated biopsy site assists in controlling bleeding if it does occur.⁶ The Gelfoam sections are back-loaded into the introducer sleeve of the SURGITIE (pre-tied loop ligature) system, introduced through the trocar, and pushed into the abdominal cavity with the plastic rod. If generalized liver disease is present, marginal biopsy samples are obtained from the edge of the liver lobe (Figure 7-5A-C). The 5 mm biopsy forceps are passed through the port, opened, and positioned on tissue. Pressure is held for approximately 30 seconds and then the forceps are rocked or twisted until the tissue is detached. The Gelfoam samples are then nudged into the defect with the forceps to assist in hemostasis. A minimum of five samples are taken: one or two for histology, one for culture, and three to five for heavy metal analysis. If a discrete lesion is identified, the biopsy cup forceps can be used to obtain a sample as just described, or a needle aspirate or core biopsy can be performed under direct visualization. For these biopsies, the needle is inserted through the abdominal wall, directly above and perpendicular to the lesion. Under direct observation, the needle is inserted into the core of the lesion and the syringe is aspirated or the barrel of a core biopsy needle is advanced to obtain the specimen. Suspending ventilation during this step helps avoid tearing the hepatic capsule. Aspirates of the gallbladder can be obtained using a spinal needle. To minimize bile leakage, the needle is introduced through hepatic parenchyma before entering the gallbladder.

Laparoscopic Intestinal and Pancreatic Biopsy. To reduce operative time and the potential for abdominal spillage, intestinal biopsy procedures begin with laparoscopic exploration for assessment of the liver and biliary tract and pancreatic biopsy. The procedure is then converted to a mini-laparotomy for obtaining multiple biopsy samples of the intestinal tract.

The initial 5 mm port is placed on midline just caudal to the umbilicus. A second 5 mm port is placed in the cranial right quadrant for insertion of biopsy and grasping forceps. Following liver biopsy and aspiration of the gallbladder, the biliary tree is examined. If there is dilation of the common bile duct and cystic duct, the region where the biliary and pancreatic secretions enter the duodenum must be seen. Visualization is obtained by elevating the duodenum and retracting it medially and caudally. If white, plaque-like discoloration of the pancreas is seen, a biopsy of that area should be obtained, as this can be an early sign of pancreatic adenocarcinoma. Biopsy samples can be obtained with the 5 mm cup forceps. Bleeding is minimal. The remainder of the left and right lobes of the pancreas can be visualized by applying traction to the duodenum and elevating the greater curvature of the stomach. To examine the bowel laparoscopically, a third port is placed for insertion of another pair of grasping forceps and a “hand-over-hand” technique is used to trace the bowel.

Usually, it is easier and quicker to visually examine the colon laparoscopically and then convert to a mini-laparotomy. To do so, the trocars are removed and the midline incision is extended cranially and caudally along the linea for a total length of ~ 5 cm. A loop of intestine is grasped and traced orally and aborally to completely examine and palpate the small intestine, mesentery, and mesenteric lymph nodes. Only a portion of the intestine is exposed and the remainder is returned to the abdominal cavity as the exploration proceeds. The entire intestinal tract is examined and full thickness biopsy samples of the stomach duodenum, jejunum, and ileum are obtained. The stomach may be difficult to expose, and if needed, the incision can be extended cranially.

Prior to closure, the abdomen should be inspected to ensure hemostasis. If the animal is hypotensive during surgery, bleeding can occur when the abdominal pressure is reduced and blood pressure returns to normal. If there is concern for active bleeding or contamination from the biopsy procedure, abdominal lavage and inspection should be performed prior to closure. The midline incision and trocar sites are closed in layers.
 

Laparoscopic Ovariectomy, Ovariohysterectomy

Indications

This procedure is indicated for elective sterilization or retrieval of ovarian remnants left from an incomplete ovariectomy. Studies have demonstrated that there is no increase in complications, such as weight gain, stump pyometra, urethral sphincter incompetence or uterine neoplasia associated with ovariectomy versus ovariohysterectomy. However, it is wise to be specific in discharge instructions for clients as to the procedure being performed to avoid potential future misunderstanding if the animal is seen by another veterinarian. Recently, randomized studies demonstrated that dogs undergoing laparoscopic ovariohysterectomy required less postoperative analgesia than those undergoing an open procedure.^7,12 Another study demonstrated less decrease in postoperative activity levels with laparoscopic approaches in small dogs, compared to open surgery.¹

Equipment for dogs > 25 kg

• 10 mm blunt-tip trocar-cannula (with reducing cap to be compatible with 5 mm laparoscope)
• 5 mm sharp trocar-cannula
• 5 mm grasping forceps
• Laparoscopic spay hook or large curved needle
• 5 mm LIGASURE device, ENSEAL or Harmonic scalpel

As a general guideline, in cats and very small dogs a 2.7 mm rigid scope is used; for dogs < 25 kg, a 5.0 mm laparoscope is used, and for dogs > 25 kg, a 10 mm laparoscope is used. The size dictates the size of the Hasson trocar, which is placed on midline, just caudal to the umbilicus.

Technique

The abdomen is insufflated to 12 mm Hg and the abdomen is explored. A second 5 mm port is placed on midline about halfway between the umbilicus and pubis. The grasping forceps are inserted and the animal is rotated to the right to expose the left uterine horn and ovary. Grasping forceps are used to grasp the proper ovarian ligament and elevate the ovary to a convenient location on the body wall (Figure 7-6A-F). The location must be inside the sterile field, hence a wide surgical clip and preparation are needed. A laparoscopic spay hook is inserted through the body wall and the ovary is draped over the hook as it is rotated to engage the tip in the body wall. If a needle and suture are used, the needle is rotated and removed from the body and forceps are attached to the suture and used to elevate the ovary and body wall. For secure and rapid hemostasis, an energy system such as the LIGASURE or Harmonic Scalpel is used. The jaws of the device are positioned across tissue, energy is applied, and the tissue is cut. The ovarian pedicle and suspensory ligament are cut first, followed by transection of the fallopian tube and proper ovarian ligament or the proximal portion of the uterine horn. Hemostasis is complete and the ovary is left suspended to the abdominal wall. The energy device is removed and the laparoscope is transferred to the caudal port. Grasping forceps are inserted through the subumbilical port to grasp the ovary as the needle or spay hook is released. The tissue is then removed with the trocar by detaching the sutures from the olive plug. Following inspection to ensure that the entire ovary was removed, the trocar is replaced and the procedure is repeated on the right side. Following final inspection to ensure hemostasis, the insufflation is relieved, and port sites are closed in 2 layers. A 5% lidocaine patch is applied to the skin around the port sites and postoperative analgesia is provided with nonsteroidal anti-inflammatory medication and injectable opioid pain medication.

Complications are rare, and the most common are inflammation of the port sites. Iatrogenic trauma to the spleen or other abdominal organs during insertion and removal of laparoscopic equipment, electrocautery injury to surrounding tissue, and subcutaneous emphysema may occur. Usually these complications are self-limiting and are treated conservatively with no serious consequence.

A laparoscopic ovariohysterectomy can be performed using a similar approach; however, with only one working port, it can be difficult to mobilize the ovary and keep it retracted to gain access to the broad ligament. If so, one can place an additional port so that caudo-medial retraction can be provided while the energy modality is used to coagulate and divide the broad ligament to the level of the uterine arteries and uterine bifurcation. Once both broad ligaments are transected, the uterine body is coagulated and cut or ligated. If the uterine body is small, the LIGASURE, ENSEAL, or Harmonic Scalpel can be used to coagulate and cut it. If very large, the uterine body may need to be ligated. The caudal midline trocar is removed and the incision enlarged so that the uterine body is exteriorized. An extracorporeal ligature can then be used to ligate the uterine body in the same fashion as in open surgery (technically performing a laparoscopic-assisted ovariohysterectomy). Another alternative is to use a pre-tied loop suture. The pre-tied loop is introduced and the ovaries and uterine horns are passed through it such that the loop can be positioned on the uterine body. A nylon cannula is broken and advanced to tighten the loop, taking care to avoid incorporation of other structures into it. When the loop is tight, the suture tail is cut with laparoscopic scissors. The uterus is then transected and removed from the sub-umbilical port.

If the tissue is suspected to be malignant or infected, a specimen retrieval bag can be utilized to protect the body wall from contamination. The bag is introduced through one of the ports, tissue is placed in it and the mouth of the bag is closed for withdrawal from the body. Final inspection is performed and the port sites are closed routinely.
 

Cryptorchid Castration

Indication

This procedure is indicated for animals that have intra-abdominal retained testicles, which are susceptible to torsion and neoplasia. A laparoscopic or laparoscopic-assisted technique can be performed, depending on available equipment. If an energy modality such as LIGASURE, ENSEAL, or Harmonic Scalpel is available, the laparoscopic approach is performed. If not, the laparoscopic-assisted technique is easiest and quickest.

Equipment

• 10 mm blunt-tip trocar-cannula (with reducing cap to be compatible with 5 mm laparoscope)
• 5 mm sharp trocar-cannula
• 5 mm grasping forceps
• Laparoscopic spay hook or large curved needle
• 5 mm LIGASURE device, ENSEAL or Harmonic scalpel

Technique

With both techniques, the animal is positioned in dorsal recumbency and prepared for abdominal surgery. Following the guidelines described earlier, a Hasson port is placed on midline caudal to the umbilicus. The abdomen is insufflated and inspection is performed. Once the testis is identified, a second 5 mm or 10 mm port is placed under direct visualization in the caudal abdominal quadrant on the side opposite the location of the testicle if performing a totally laparoscopic procedure (Figure 7-7 A-D). If the laparoscopic assisted technique will be utilized, the port is placed on the same side as the retained testicle. If both testicles are retained, they can usually be retrieved through the same port with the laparoscopic technique. The port is ideally placed just lateral to the lateral edge of the rectus abdominis muscle, taking care to avoid the caudal deep epigastric vessels.

If the laparoscopic assisted technique is used, the testicle is identified and elevated to the body wall. The trocar is removed and the testicle is exteriorized. It may be necessary to enlarge the incision, depending on the size of the laparoscopic port. Similar to open surgery, ligation of the gubernaculums, pampiniform plexus, and spermatic cord is performed. If both testicles are retained, it may be necessary to place a second working port in the opposite caudal abdominal quadrant for removal of the second testicle. Following final inspection to ensure hemostasis, the port sites are closed routinely.

When the 2-port laparoscopic technique is used for a totally laparoscopic procedure, the testicle is lifted suspended from the abdominal wall with a percutaneous suture, similar to the technique used for ovarian suspension in the laparoscopic ovariectomy. The LIGASURE, ENSEAL, or Harmonic Scalpel are used across the gubernaculums, pampiniform plexus, and spermatic cord. Alternatively, clips or sutures can be used. Once ligation and transection are complete, the testicle is removed. If a 10 mm port is placed on midline, the testicle can be removed from that port by transferring the laparoscope to the caudal port. Following final inspection, the port sites are closed routinely.
 

Gastropexy

Indications

Prophylactic gastropexy is performed to prevent gastric volvulus in large breeds of dogs that may be predisposed to developing gastric dilatation-volvulus syndrome. The procedure can be combined with laparoscopic ovariectomy in female dogs or castration in male dogs. In females, the laparoscopic-assisted procedure is performed; in males, an endoscopic-assisted procedure using a flexible endoscope avoids the need to use laparoscopic equipment. The technique is an incisional gastropexy procedure performed by suturing the seromuscular layer of the stomach to the internal fascia and transverse abdominis muscle at a site selected approximately 3 cm caudal to the costal margin on the right side. Biomechanical studies and clinical experience suggests that the resultant gastropexy adhesion is strong and reliable.⁸

Equipment

• Laparoscopy equipment for the laparoscopic-assisted approach 10 mm blunt-tip trocar-cannula (with reducing cap to be compatible with 5 mm laparoscope)
• 10 mm sharp trocar-cannula
• 10 mm endoscopic Babcock forceps
• Flexible endoscope for the endoscopic-assisted approach
• 76-mm long needle with size-2 polypropylene suture

Technique

Laparoscopic Approach. Following general anesthesia and positioning in dorsal recumbency, the abdomen is prepared for abdominal surgery. The monitor is placed at the animal’s head and the surgeon stands on the animal’s right side. A 10 mm Hasson port placed on midline, just caudal to the umbilicus serves as the camera port. The abdomen is insufflated to 12 mm Hg and inspected. Particular attention is paid to the location of the stomach, omentum, and spleen. The pylorus is identified beneath the right medial liver lobe and gallbladder. A second 10 mm port is placed 3 to 5 cm caudal to the ribs on the right side at the lateral edge of the rectus abdominis muscle. Babock forceps are introducted to elevate the liver lobes and fully expose the ventral aspect of the stomach (Figure 7-8A-H). Using the aperture of the Babcock forceps as a measuring tool, a site is selected in the antral region of the stomach approximately 5 cm orad to the pylorus and midway between the greater and lesser curvatures of the stomach. The gastric wall is grasped firmly and elevated to the body wall as the trocar cannula is withdrawn.

When the Babock forceps reach the abdominal wall, the skin and abdominal fascial incisions are extended to ~ 5 to 6 cm with a scalpel blade under laparoscopic visualization. Pneumoperitoneum is lost as the incision is extended and the insufflation gas is turned off. Bleeding is minor. Two stay sutures are placed in the gastric wall about 5 cm apart and the Babcock forceps are removed. Two Gelpi retractors or the Lone Star Veterinary Retractor system with multiple elastic stays can be helpful to aid in exposure and identification of the layers of the abdominal wall. The seromuscular layer of the stomach is then sutured to the abdominal wall with size 2-0 absorbable suture. The external fascia, subcutaneous tissue, and skin are closed routinely. Following inspection of the gastropexy site to ensure that there is no twisting of the gastric wall, the abdomen is desufflated, the umbilical port is removed, and the fascia, subcutaneous tissue and skin are closed. An alternative, totally laparoscopic, approach is direct laparoscopic suturing of the gastric seromuscular incision to an incision in the peritoneum and transversus abdominis muscle with traditional needleholders, barbed sutures, or using the ENDOSTITCH device.⁹

Endoscopic Approach. A flexible endoscope is passed to inspect and dilate the stomach with air. The animal is tilted to the left approximately 30 degrees to allow the distended stomach to be in contact with the right lateral body wall caudal to the costal margin. With gastric distention, identification of the pylorus, and indention from forceps applied to the body wall, the correct site for gastropexy is identified.¹⁰ A large needle is passed percutaneously under direct vision with the endoscope into the stomach and back out through the abdominal wall. A second suture is placed under direct vision from the endoscope 4 to 5 cm from the first suture. Externally, an incision is made through the skin and abdominal wall between the 2 sutures. The gastric surface is identified and a 3 to 5 cm seromuscular gastric incision is made, avoiding the mucosa. Similar to the laparoscopic assisted gastropexy, the seromuscular layer of the stomach is sutured to the body wall and closure proceeds as described previously. The stay sutures are removed and final endoscopic inspection is performed. The surgeon should be alerted to the possibility of trapping of omentum or abdominal contents between the gastric and abdominal wall so careful identification and palpation should be performed prior to placing the percutaneous sutures.
 

Laparoscopic-assisted Cystoscopy

Indications

This procedure is performed when the surgeon desires to minimize the approach to bladder biopsy (Figure 7-9A-E) or management of urinary calculi that are too large or too numerous for other less invasive treatment modalities.¹¹ Most often, the procedure is performed in male dogs because stones are more easily retrieved from the urethra in female dogs. The benefit of this procedure is that the incisions are very small and there is less likelihood of urine contamination of the abdomen. Preoperative patient management practices and preparation are similar to open cystotomy.

Equipment

• 30 degree rigid cystoscope, 1.9 mm for small dogs and cats, 2.7 mm for most other dogs
• Saline irrigation fluids with pressure bag and ingress/egress tubing Stone Basket, compatible with insertion through the working channel of the cystoscope
• Arthroscopy or alligator forceps
• 2 trocars, either 5 mm or 10 mm, depending on the laparoscope size
• 5 and/or 10 mm Babcock grasping forceps
• 5 mm disposable screw tipped trocar (optional)

Technique

The initial port is placed on midline near the umbilicus for insertion of the laparoscope. Following insufflation and inspection of the abdomen, a second 5 mm or 10 mm port is placed to exteriorize the bladder. In females, it is placed on midline; in males, the second port is placed lateral to the prepuce at the lateral edge of the rectus abdominis muscle. Through the second port, grasping forceps are introduced to grasp the apex of the bladder and elevate it to the body wall as the trocar is removed. Usually, a 10 mm incision is sufficient unless a very large stone is being removed, but a 5 mm port will need to be enlarged. Stay sutures are placed in the bladder wall and a stab incision is made into the bladder with a #11 scalpel blade. The bladder wall can be sutured to the skin to prevent abdominal contamination during the procedure or a 5 mm disposable screw tipped trocar can be positioned if repeated insertions of the cystoscope are anticipated. The insufflator is turned off and the laparoscope is disconnected from the camera and light guide cable. The camera and light cable, along with the ingress and egress fluid lines, are then attached to the cystoscope. The cystoscope is inserted into the bladder, the fluids are turned on, and thorough visual inspection of the bladder is performed. In male dogs, it can be helpful to pass a urinary catheter to assist in occluding the urethral lumen so that stones do not lodge in the urethra during cystoscopy. At the end of the procedure, the urethra can be flushed with the catheter to ensure that all stones are retrieved. A flexible endoscope can also be used to inspect and/or retrieve urethral calculi.

One of several methods may be used for stone retrieval, depending on the size and number of cystoliths present. The wire stone basket is efficient for removal of large numbers of small calculi that stick together with blood clot. The basket is passed through the working channel of the cystoscope and, under direct vision, passed past the calculi and opened. As the basket is closed, the stones are brought to the end of the cystoscope and the cystoscope is removed from the bladder to deliver the stones. If calculi are too large for the stone basket, they can be retrieved with forceps inserted beside the cystoscope. Numerous small calculi can be removed by using a suction device in the bladder and flushing the urethral catheter. At the end of the procedure, the urethral catheter is withdrawn and the cystoscope is positioned in the trigone region of the bladder. The urethral catheter is simultaneously flushed and passed, and any remaining stones are seen as they are flushed back into the bladder. Bladder polyps or biopsy can be performed with either cystoscopic technique using a biopsy forceps or externally, if full-thickness resection is needed.

The cystotomy is then closed and the bladder is returned to the abdominal cavity. The caudal incision is closed, the laparoscope is re-attached to the camera and light guide cable, and the abdomen is re-insufflated. Following final inspection, the camera port is removed, the CO₂ is allowed to escape and the port site is closed routinely. Although always a concern, seeding of the abdominal wall with tumor cells following biopsy of transitional cell carcinoma has not occurred.
 

References

1. Culp WT, Mayhew PD, Brown DC. The effect of laparoscopic versus open ovariectomy on postsurgical activity in small dogs. Vet Surg 2009; 38:811-817.
2. Nadeau O, Kampmeier O. Endoscopy of the abdomen: abdominoscopy: a preliminary study, including a summary of the literature and a description of the technique. Surg Gynecol Obstet 1925; 41:259-271.
3. Bailey JE, Pablo LS. Anesthetic and physiologic considerations for veterinary endosurgery. In Freeman LJ (ed). Veterinary Endosurgery. St. Louis: Mosby, 1999.
4. Stoloff DR. Laparoscoic suturing and knot tying techniques. In Freeman LJ (ed). Veterinary Endosurgery. St. Louis: Mosby, 1999.
5. Freeman L, Rawlings CA, Stoloff DR. Endoscopic knot tying and suturing. In Tams TR and Rawlings CA (eds), Small Animal Endoscopy, 3rd edition. St. Louis: Elsevier-Mosby, 2011.
6. Freeman LJ. Laparoscopic liver biopsy. Clinician’s Brief, May 2010.
7. Hancock RB, Lanz OI, Waldron DR, et al. Comparison of postoperative pain after ovariohysterectomy by harmonic-scalpel-assisted laparoscopy compared with median celiotomy and ligation in dogs. Vet Surg 2005; 34:273-282.
8. Rawlings CA, Foutz TL, Mahaffey MB, Howerth EW, Bement S, Canalis C. A rapid and strong laparoscopic-assisted gastropexy in dogs. Am J Vet Res 2001; 62:871-875.
9. Mayhew PD, Brown DC. Prospective evaluation of two intracorporeally sutured prophylactic laparoscopic gastropexy techniques compared with laparoscopic-assisted gastropexy in dogs. Vet Surg 2009; 38:738-746.
10. Dujowich M, Reimer SB. Evaluation of an endoscopically assisted gastropexy technique in dogs. Am J Vet Res 2008; 69:537-541.
11. Rawlings CA, Mahaffey MB, Barsanti JA, Canalis C. Use of laparoscopic-assisted cystoscopy for removal of urinary calculi in dogs. J Am Vet Med Assoc 2003; 222:759-761.
12. Devitt CM, Cox RE, Hailey JJ. Duration, complications, stress, and pain of open ovariohysterectomy versus a simple method of laparoscopic-assisted ovariohysterectomy in dogs. J Am Vet Med Assoc. 2005 Sep 15;227(6):921-7.
     

Introduction

Thoracoscopy is a minimally invasive technique for viewing the internal structures of the thoracic cavity. The procedure uses a rigid telescope placed through a portal positioned in the thoracic wall in order to examine the contents of the pleural cavity. Once the telescope is in place, either biopsy forceps or an assortment of surgical instruments can be introduced into the thoracic cavity through adjacent portals in the thorax to perform various diagnostic or surgical procedures.

The minimal invasiveness of the procedure, the rapid patient recovery, and diagnostic accuracy make thoracoscopy an ideal technique for selected cases over more invasive procedures. Small animal thoracoscopy has not only developed into a diagnostic tool but more recently has progressed to become a means for performing minimally invasive surgical procedures.^1-4

Despite the advent of newer laboratory tests, imaging techniques and ultrasound directed fine needle biopsy or aspiration, thoracoscopy remains a valuable tool when appropriately applied in a diagnostic plan. Thoracoscopy may also provide accurate and definitive diagnostic and staging information that would otherwise only be obtained through a surgical thoracotomy.^5-6

Indications and Contraindications

The most common indication for thoracoscopy is to examine and biopsy thoracic organs or masses. Thoracoscopy is also a means of performing various surgical procedures. Thoracoscopy may not completely replace an exploratory thoracotomy but can provide a minimally invasive means of accomplishing a number of diagnostic and surgical procedures in small animals.

Diagnostic thoracoscopy is commonly used as a method for obtaining pleural biopsy, lung biopsy, cranial mediastinal and lymph node biopsy. Common surgical techniques currently being performed in small animals include partial pericardectomy or pericardial window, patent ductus arteriosus, lung lobectomy, resection of cranial mediastinal mass, correction of vascular ring anomalies, thoracic duct ligation, and debridement for the treatment of pyothorax. The advantages of surgical thoracoscopy over conventional open surgical exploratory thoracotomy include improved patient recovery because of smaller surgical sites, lower postoperative morbidity with lower infection rates and decreased postoperative pain.

Thoracoscopic Equipment

The basic equipment required for diagnostic thoracoscopy includes a telescope, corresponding trocar–cannula units, light source, and various forceps and ancillary instruments.7-9 The telescope most commonly used by the author is a 5 mm diameter 0° field of view telescope for routine diagnostic thoracoscopy. The 0° designation means that the telescope views the visual field directly in front of the telescope. Angled viewing scopes, the most common being a 30° telescope, views in a 30° downward direction. The angled telescopes enable the operator to look over the top of organs and view in small areas which is very useful during thoracoscopy to look at hilar lymph nodes, around the base of the heart, the hilus of lungs during lobectomy, and the mediastinum.

The telescope is attached to a light source using a light guided cable. A Xenon light source with a high intensity is considered to give the truest colors of abdominal organs and is recommended. A high intensity light source provides enough light for deep chested dogs. The telescope is also attached to an endoscopic video camera which allows the image to be viewed on a monitor. 

Open or closed cannulas can be used to perform thoracoscopy. With closed cannulas, a controlled pneumothorax can be induced and a ventilator is not required. With open cannulas, a ventilator is required because the pleural space is open to the environment. Open cannulas are recommended to perform thoracoscopy because they eliminate the risk of tension pneumothorax especially when advanced surgical procedures are performed. The open cannulas can be either soft or hard. Soft cannulas are less traumatic to the intercostal artery and nerve, and can be cut to a desired length therefore they do not protrude excessively into the thoracic cavity. Rigid cannulas are required for a transdiaphragmatic sub-xiphoid approach. Rigid cannulas protect the telescope better when an intercostal approach is performed. Ribs are very rigid and it is easy to bend or even break a scope if there is no cannula to move the ribs with. Closed or open cannulas are placed over a blunt trocar into the thoracic cavity. Cannulas exist in a wide variety of diameters. Diameter of the cannulas is determined by the instruments that will be used during the procedure. For example, the stapling equipment used for lung lobectomy comes in a 12 mm diameter. Therefore, a 12 mm cannula will have to be placed for the introducation of the stapling equipment. Thoracoscopy can be performed without cannulas. However, this technique increases the risk of damaging the intercostal nerve and artery. This approach is reserved for small size animals since cannulas take up excessive space in their thoracic cavity.

During diagnostic thoracoscopy, a number of accessory instruments are essential.^6,8,9 A palpation probe is required to move and palpate the thoracic organs. Most palpation probes have centimeter markings so one can estimate the relative size of organs or lesions. The palpation probe can also be used to apply pressure on a biopsy site that is bleeding excessively. Biopsy forceps are used for biopsy of lymph nodes, and pleura.

Surgical thoracoscopy often requires a vast array of instruments designed for specific indications. Common instruments include grasping forceps, scissors, aspiration tubes and clip applicators. Certain specialized instruments such as stapling devices are generally 10 to 12 mm in diameter. Many of the surgical instruments also have capabilities for monopolar electrosurgery at their distal tip. Retractors are very important during thoracoscopy because they allow retraction of lungs. With retractors, lung lobes can be removed without using one-lung ventilation.

Approaches

Since ribs are supporting the thoracic wall, the chest wall cannot be distended to create a working space. Different options are available to increase working space. First, lung tidal volume can be decreased on the ventilator and the frequency of ventilation increased. This will reduce the volume of the lungs without reducing ventilation. This will expand the surgical field enough to be able to perform diagnostic thoracoscopy. Second, one-lung ventilation can be instituted to completely collapse the lung on one side of the thoracic cavity.^10,11 One-lung ventilation induces a right to left shunt that results in desaturation of oxygen in arterial blood. To further assist patient ventilation, it is recommended to use positive end expiratory pressure since it does not reduce cardiac output but maintains open alveoli in the dependent ventilated lung. One-lung ventilation is mostly used with an intercostal approach when a lung lobectomy is performed. Different techniques have been described to achieve one-lung ventilation in dogs. Selective bronchial intubation with a long small diameter endotracheal tube can be used.¹² This technique works most effectively for selective ventilation of the left lung. Since the bronchus of the right cranial lung lobe is so cranial, it is difficult to perform selective intubation of the right lung. A double-lumen endotracheal tube can be used to intubate the left and right lung lobes. This approach allows one branch of the tube to be occluded so that the other lung can be selectively ventilated. Again, because of bronchial anatomy this technique is not very efficient in dogs. Introduction of an endobronchial occluder is commonly used in dogs to induce one-lung ventilation.^10,11,13 The occluder is advanced either through or along the endotracheal tube and is positioned under bronchoscopic guidance. After placement of the occluder in the desired position, the balloon at the end of the occluder is inflated to occlude the bronchi. It is important to induce one-lung ventilation with this technique, after the dog has been positioned for surgery. Manipulation of the patient can easily dislodge the ballon and cause complete occlusion of the trachea. When one-lung ventilation is used it is critical that a capnograph is used to monitor carbon dioxide production and patency of the airway. Third, carbon dioxide insufflation can be used to collapse the lung lobes.¹⁴ This technique creates a pneumothorax and the amount of pressure in the pleural space will control the degree of the pneumothorax. This technique is not currently used in veterinary medicine. It can induce severe atelectasis and severe desaturation of oxygen in the arterial blood. This technique has been used to visualize specific areas of the pleural space.

Thoracoscopy can be performed using either a trans-diaphragmatic or an intercostal approach.^7,12,15 The trans-diaphragmatic approach allows visualization of both hemi-thoraces. A long-axis view of the thorax is then obtained. This is the approach of choice for exploration of the thoracic cavity and biopsy. An intercostal approach is indicated for surgical thoracoscopy because it allows very good visualization of specific structures in the affected hemithorax.

Transdiaphragmatic Sub-xiphoid Approach

The patient is positioned in a dorsal recumbent position. First, a screw-in cannula is inserted from a sub-xiphoid position in a cranial direction. Before insertion of the screw in the cannula, a small skin incision is performed caudal to the xiphoid. The cannula is screwed into the thoracic cavity under thoracoscopic visualization. After penetration of the thoracic cavity by the cannula, the thoracoscope is advanced into the thoracic cavity. After initial exploration of the thoracic cavity, two other cannulas are placed under thoracoscopic visualization to allow utilization of instruments. These cannulas are placed in intercostal spaces according to the location of the lesions, which require exploration or treatment. Cannulas need to be placed as ventral as possible to allow maximum mobility of the instruments. Metzenbaum scissors with electrocautery and grasping forceps are used to incise the mediastinum. This will allow exploration of both hemithoraces. A 0° telescope is used for initial exploration. 

Intercostal Approach

Positioning of the patient is very important during an intercostal approach since it uses gravity to move lungs and heart within the thoracic cavity. Patients can be placed in ventral recumbency for exploration of the thoracic duct or in an oblique position to be able to visualize the hilus of the lungs during lung lobectomy.

During an intercostal approach, all the cannulas are placed in intercostal spaces in a triangular fashion around the organ or the lesion to be explored. Cannulas can be introduced from the third to the ninth intercostal space. The cannula used for the introduction of the telescope is usually placed as far as possible from the organ or the lesions to be biopsied or resected. After incising the skin with a #10 blade, a mosquito forceps is used to bluntly dissect through the intercostal space. The thoracoscopic cannula is then bluntly introduced into the intercostal space, and into the pleural space. Cannulas can be introduced at any level from dorsal to ventral in the intercostal space.
 

This topic is written based on the available literature through 2010 and does not cover the most current literature on this topic.

Introduction

Arthroscopy is the technique of endoscopic examination of a joint. The use of arthroscopy is growing rapidly in small animal orthopedic practice for several reasons. Arthroscopy is significantly less invasive than a traditional arthrotomy and both veterinarians and pet owners are seeking to minimize pain associated with surgical trauma. The excellent visualization provided by arthroscopy has led to the discovery of new joint diseases and for certain diseases such as ligamentous instability of the shoulder or medial compartmental disease of the elbow it may be the only practical method of diagnosis. Arthroscopy provides increased magnification and visualization of joint structures and this may be its greatest advantage over traditional surgical techniques.

Magnification has provided new understanding of the devel- opment of osteoarthritis in small animals. For example, it is now known that osteoarthritis of the canine elbow affects the medial compartment much more severely than the lateral compartment (medial compartment disease). Arthroscopy has also demon- strated that osteoarthritic lesions may occur in sites identical to that of osteochondritis dissecans (OCD) in the shoulder or stifle without diagnostic radiographic findings. Finally, arthroscopy has the ability to diagnose and grade osteoarthritis much earlier and with greater accuracy than radiography in virtually all joints (Table 7-1).

Other advantages of arthroscopy include the ability to perform procedures that are not possible with arthrotomy. The use of radiofrequency therapy for joint stabilization is only possible through arthroscopy. Topical osteoarthritis treatment using microfracture or abrasion techniques can be performed more precisely with arthroscopy due to the magnification that arthroscopy provides. A contributing factor to the increased use of arthroscopy in small animals has been the development of smaller but high quality instrumentation. Arthroscopes of 1.9 to 2.7 mm in diameter are routinely used in small animals and in the near future diagnostic arthroscopes as small as 1.1 mm in diameter will be available for outpatient diagnosis and follow up procedures (second look arthroscopy). Client demand has also stimulated the increased use of arthroscopy. Many pet owners are knowledgeable regarding arthroscopy and understand the benefits of minimally invasive surgical technique. The ability to provide arthroscopy in small animals allows veterinarians to provide advanced orthopedic diagnosis and therapy. Although increased expense is associated with arthroscopy, I have found most clients willing to incur the increased cost due to the previously mentioned advantages of the procedure (Table 7-2).

Arthroscopy presents challenges but has few disadvantages. Arthroscopic equipment is expensive and requires specialized care and handling. The cost for an arthroscopy system varies considerably with equipment selected. In addition, becoming proficient in arthroscopy both diagnostically and therapeutically can be difficult and requires considerable time. The skills involved in arthroscopy are considerably different from those of traditional surgery although some principles remain the same.

Continuing education courses are available for training in small animal arthroscopy and veterinarians interested in becoming proficient are encouraged to gain experience in the teaching laboratory. Iatrogenic damage to the joint and the equipment is common during the learning process. Initially, performing an arthroscopic procedure will require more time than traditional surgery but with increasing experience arthroscopic procedures become faster than open surgery. Arthroscopy seems likely to become the standard of care for many diagnostic and therapeutic procedures involving the joints of companion animals.
 

  
Basic Terminology

Arthroscopy is the technique of endoscopy of a joint. Instrumentation refers to the insertion of an arthroscope or other instruments into the joint. Triangulation refers to successful visualization of the hand instruments through the arthroscope in a manner that is conducive to performing biopsies or therapeutic procedures within the joint. All equipment inserted into the joint is done through portals or holes established through the skin and soft tissues. Cannulas are metal tubes that maintain the portals and protect the instruments during the procedure. Arthroscopes are always used through specifically designed cannulas. Other instruments and fluid outflow devices may be used with or without cannulas. Fluid flowing into the joint is referred to as in-flow or ingress while fluid flowing out of the joint is referred to as out-flow or egress. Portals are defined by their use. The arthroscope is inserted through a scope or camera portal and power and hand tools are inserted through an instrument portal. Repeat arthroscopic examination of a joint that has been previously scoped is referred to as second-look arthroscopy.

Instrumentation Arthroscopes differ in diameter (1.9, 2.3, 2.7 mm and larger), length (short, long) and angle. Arthroscopes in common use in small animal arthroscopy include any of the diameters and lengths described and most scopes have a 30° angle. The diameter designates the telescope diameter alone and does not include the diameter of the arthroscope cannula, which is necessary for use. The selection of diameter is based on the size of the joint and surgeon preference with larger scopes providing more rigidity and greater field of view and smaller scopes causing less iatrogenic damage and having greater mobility.

The camera head attaches to the arthroscope eyepiece. Cameras are digital and available as 1 or 3 chip and must be used with a specific camera box that processes the image for the video monitor. For general use, 1-chip cameras provide excellent resolution and recording capabilities and 3 chip cameras are only necessary for video or still image work that is to be published. Medical grade video monitors are recommended to provide a bright, clear, and accurate image. Most new light sources use xenon lamps, which provide increased light intensity and higher color temperature than halogen and therefore provide higher visual clarity and truer color. Xenon light sources are more expensive than halogen but are recommended for superior image quality.

Fluid flow during arthroscopy helps maintain joint distention, aids in clearing blood and other debris from the joint, and decreases the risk of joint contamination. Fluid may be delivered to the joint by gravity or from an arthroscopic pump. The use of lactated ringers solution as lavage fluid is preferred over saline as the former is thought to be less destructive to articular cartilage. Fluid outflow is provided by either a disposable needle or a specific outflow cannula.

The majority of arthroscopic therapy is performed with hand instrumentation. Both hand instruments and power tools are inserted into the joint through an instrument portal that may be used with or without a cannula. Hand instruments include probes, knives, curettes, and forceps. The most commonly used probes are right angled and may have calibration marks for measurement of lesions. Numerous styles of knives and curettes are available for manipulations of soft tissue. The most common forceps used in small animal arthroscopy are graspers for removal of hard or soft tissues and biters for debridement of soft tissues.

Power instruments are not necessary for basic small animal arthroscopy but increase the surgeon’s efficiency and capabil- ities. The most common power instrument used is a shaver. These motorized hand tools have numerous tip designs including burrs, sharp cutters, and aggressive cutters. Additional power instruments include electrocautery and radiofrequency. Electrocautery tips specific for use in arthroscopy are available for some electrocautery generators. Alternatively, cautery may be performed by use of a radiofrequency unit. These units, which are available in both bipolar, and monopolar designs have also been advocated for soft tissue ablation and collagen shrinkage.

Arthroscopy of the Shoulder

Knowledge of diseases of the shoulder and their treatment has grown recently due to increased experience with shoulder ultrasound, arthroscopy, and MRI of the shoulder. The differential diagnosis for shoulder diseases has been expanded, as have the potential methods of treatment. Arthroscopy of the canine shoulder should be performed with a 2.7 mm arthroscope. A cranio-lateral or caudo-lateral arthroscope portal is generally used (Figure 7-10). Recently described portals include a medial portal using an in to out technique. Arthroscopy on the shoulder requires less equipment than other joints but can be the most difficult to instrument for beginning arthroscopists. The shoulder is also the least forgiving when mistakes in technique lead to substantial fluid leakage. Regardless, complications associated with arthroscopy of the shoulder are uncommon.

Thorough examination of the shoulder joint with the arthroscope includes assessment of the cartilage of the humeral head and glenoid cavity, evaluation of the origin of the biceps tendon and the remainder of the proximal tendon, evaluation of the subscapularis tendon, and evaluation of the medial glenohumeral ligaments. Lesions of the cartilage of the shoulder joint include OCD, focal or localized osteoarthritis, and generalized osteoarthritis. OCD is the most commonly treated disease of the shoulder joint. Arthroscopic treatment of OCD is usually rapid and highly successful. Although similar clinical results can be obtained with arthrotomy, arthroscopy can aid in retrieving fragments that have migrated and allows easier inspection of the entire lesion. Focal osteoarthritis can occur in a site identical to that of OCD. The specific cause of the lesion is unknown and it may not be apparent on radiographs. Treatment may include topical arthroscopic techniques such as microfracture or abrasion arthroplasty although the primary treatement is medical. Generalized osteoarthritis may be identified with or without other injuries to the shoulder such as tearing of the biceps tendon or collateral ligaments.

Diseases of the biceps tendon are easily diagnosed with arthroscopy since it provides outstanding visualization of this structure. Tendon tears and synovitis are readily apparent. Tears can be rapidly treated by tenotomy through a cranial portal but synovitis should not be treated with tenotomy since it may be an indication of other joint disease.

Arthroscopy has demonstrated that many dogs suffer from damage to the supportive structures of the shoulder including the medial and lateral collateral ligaments and the subscapularis tendon. Other supportive structures with the exception of the biceps tendon cannot be visualized through an arthroscope. If damage to these structures is identified they may be treated by arthrotomy and ligament reconstruction or through arthroscopy by the use or radiofrequency that shrinks collagen thereby eliminating instability.
 

Arthroscopy of the Elbow

Elbow dysplasia is the most common cause of forelimb lameness in dogs. The ability to diagnose and treat this widespread disease has improved through the use of arthroscopy. The single greatest lesson learned from elbow arthroscopy is “for a forelimb lameness of unknown origin, arthroscopy of the elbow should be part of the diagnostic plan.” Justification for this philosophy is the high prevalence of elbow osteoarthritis found during arthroscopic examination in spite of normal radiographic findings.

The two primary indications for elbow arthroscopy are for diagnosis of suspected elbow joint disease and for treatment of elbow dysplasia. It is well recognized that osteoarthritis and fragmented coronoid process (FCP) can be present with minimal radiographic changes (Figure 7-11). Correct diagnosis of these cases may be impossible without arthroscopic examination due to minor radiographic changes. Arthroscopic examination permits thorough exploration of the joint with a minimally invasive technique and enables increased visualization of all important regions of the joint. Fragmentation of the medial coronoid process is easily visible with arthroscopy as is cartilage damage.

Once disease of the elbow joint is confirmed, arthroscopy permits treatment of most of these diseases with methods that may be more effective and are less invasive than arthrotomy. Arthroscopy permits rapid and easy removal of loose fragments due to OCD or FCP. Areas of cartilage damage may be treated with topical management such as microfracture or abrasion arthroplasty. These two techniques produce bleeding at the site of cartilage disease which encourages the formation of fibrocartilage.

Abrasion arthroplasty is performed with a hand burr or preferentially a power shaver burr. A thin layer of subchondral bone over the area of the lesion is removed until bleeding is observed in the area of cartilage loss. Microfracture is performed with an appropriately angled micropick. The pick is placed against the surface of the diseased cartilage or subchondral bone and then impacted to create microfractures into the bone marrow. These cracks allow bleeding into the diseased area, the formation of a clot, and subsequent fibrocartilage formation. Although the efficacy of these procedures is controversial, they are recom- mended in the management of elbow arthritis.

Less commonly, elbow arthroscopy has been used to treat humeral condylar fractures and ununited anconeal process. In both cases, arthroscopy is used primarily to visualize joint surfaces and assure congruency during screw insertion for stabilization of the condylar fracture or ununited anconeal process. Arthroscopy is also useful for diagnosis of incomplete fusion of the humeral condyle which is difficult to diagnose radiographically.
 

Arthroscopy of the Carpus

Arthroscopy of the carpus is uncommonly performed as there are few clinical applications. Diseases diagnosed and treated with arthroscopy have included joint infection, chip fracture removal, and cartilage assessment in association with osteoarthritis.

Arthroscopy of the Hip

The technique of arthroscopy of the canine hip was described in the early 1990’s but its use has been limited until recently. The ability to visualize the, articular cartilage, femoral capital ligament, and acetabular labrum by arthroscopy allows accurate grading of intrarticular disease. Grading of hip disease has been employed primarily in clinical research involving the use of triple pelvic osteotomy (TPO) used for treatment of juvenile hip dysplasia. Other potential clincial applications include evaluation of fractures of the femoral head and septic arthritis of the hip. Arthroscopy of the hip is potentially simpler than in other joints such as the shoulder, elbow, and stifle.The coxofemoral joint is easily entered and complete examination of the joint can be achieved quickly. Special instrumentation is not necessary for arthroscopy of the hip joint although long versions of arthroscopes (2.7 mm, 30E, long) and hand instruments are needed.

Arthroscopy of the Stifle

Arthroscopy of the stifle provides a minimally invasive method for evaluation of all structures of the stifle joint. Stifle arthroscopy is a rapid and minimally invasive method for the treatment of OCD. For the experienced arthroscopist, an OCD lesion can be quickly removed through a very small incision. The cartilage lesion may then be treated with abrasion arthroplasty or microfracture to encourage cartilage healing. Arthroscopy is also commonly used in the diagnosis and management of cruciate disease and meniscal injury (Figure 7-12). In cases where early cruciate ligament injury has occurred, diagnosis may be difficult due to the lack of palpable instability or other obvious clinical changes. Arthroscopy provides excellent visualization of the cruciate ligament and meniscus. Small tears in the meniscus are more easily seen and treated through an arthroscope than by arthrotomy. The use of arthroscopy in the management of known cruciate injury eliminates the need to incise the joint capsule which is thought by some surgeons to be the primary cause of pain following conventional arthrotomy.

The stifle joint is often difficult to visualize for inexperienced arthroscopists because there are numerous cavities within the joint and the fat pad and synovium can obscure anatomic structures. I remove a portion of the fat pad with either a power shaver or radiofrequency probe to enhance visualization of the joint. Once the fat pad has been ablated there should be a clear view of the cruciate ligaments, femoral condyles, patella, trochlear groove, long digital extensor tendon, and the medial and lateral meniscus. Arthroscopy of the stifle is also used for treatment of articular fractures and techniques are being developed for the mangement of patella luxation.

Placement of a large cannulas in the stifle joint for fluid lavage and the use of shavers for synovectomy are useful techniques employed in treating septic stifle joints. These techniques are easily mastered with experience in arthroscopy.

Arthroscopy of the Tarsus

Arthroscopy of the hock is regarded as difficult. Entry into joints with significant effusion is generally easy but entry into joints with minimal effusion is much more difficult. Hock arthroscopy is primarily used for treatment of OCD and evaluation of cartilage damage.