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Diagnostic Value of Endoscopy and Biopsy
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Table of Contents
- Nerve Studies
- Endoscopic-guided Biopsies
- Endoscopic-guided Surgical Procedures
- Complication During and After Endoscopy
Endoscopy has been used in avian medicine since the 1970s, primarily for determining gender in birds that are not sexually dimorphic. With the advent of acceptable inhalation anesthetics, the safety of this procedure has increased while the stress to the patient has decreased. Unless otherwise noted, the descriptions in this chapter are of psittacine patients and related procedures using rigid endoscopes (Fig. 24.1).
Figure 24.1. Rigid endoscopes most commonly used in avian endoscopy. Top to bottom: 1.9 mm 0°, 2.7 mm 30°, 4 mm 0°.
Endoscopes are fiberoptic probes that utilize magnification to facilitate visual inspection of internal body structures. Endoscopy can complement imaging modalities such as radiography and ultrasonography. Direct visualization of internal structures by the endoscope affords numerous advantages as a diagnostic tool (Table 24.1-Table 24.4). There are instances where the use of a semi-rigid or a flexible endoscope is advantageous. Rigid endoscopes are available in a variety of viewing angles (Fig. 24.3a and Fig. 24-3b).
While most endoscopic procedures are minimally invasive, they do require anesthesia for restraint and pain management. Endoscopic visualization performed by an experienced practitioner carries minimal risk. However, the risk increases when more invasive procedures (biopsy, surgery) are performed (Table 24.5). In order to minimize the risk to the patient and maximize the diagnostic information, the practitioner should become proficient with endoscopic location and visualization of internal structures. Cadavers are excellent training tools, as they allow immediate comparison between what is visualized endoscopically and the actual organs or gross necropsy (see Chapter 26, Diagnostic Value of Necropsy).
Table 24.1. Characteristics of Endoscopes
Note: Diameters of scopes do not include sheaths and their working channels.
Figure 24.2a. A flexible endoscope allows more maneuverability in viewing lungs and the gastrointestinal system. (Greg J. Harrison).
Figure 24.2b. The 3-mm measurement of a small, flexible endoscope. (Greg J. Harrison).
Figure 24.2c. The fiberoptic bundle (a) for light and visualization, the air or flushing port (b), and an instrument port (c) of a 3-mm flexible endoscope. (Greg J. Harrison).
Table 24.2. Light Sources
Computed flash generator
Table 24.3. Lenses for Rigid Endoscopes
Table 24.4. Viewing Angles for Rigid Endoscopes (see Fig. 24.3a and Fig. 24.3b)
Figure 24.3a. The view as seen through a 2.7-mm 30° scope. Turning the scope around its optical axis, a panoramic view is possible.
Figure 24.3b. Kidney (K), ovary (O), Ovarian ligament (OL) Intestine (I) and Spleen (S) seen with a 4-mm 0° scope. Only a straightforward view of the organs is possible.
Table 24.5. Surgical Equipment Used during Endoscopy
Most of the body can be examined using endoscopy. Apart from the visual assessment, tissue sampling is possible using the working channel and biopsy tools (Table 24.6). A sterile sheath is particularly valuable for microbiological sampling (especially of the deeper respiratory system). The sheath prevents contamination of the sample.
Table 24.6. Endoscopic Accessories (see Fig. 24.5a and Fig. 24.5b)
Flexible Biopsy Forceps
Flexible Grasping Forceps
Infusion/aspiration Needle [a]
Endoscopic-guided Surgery Equipment
Cleaning and Sterilization
New surgical procedures using multiple endoscopes, multiple sites and radical new instruments are being developed (Fig. 24.4). The use of a flexible needle can have multiple applications (Fig. 24.5a and Fig. 24.5b).
Figure 24.4. Basic equipment for endoscopic-guided multipleentry surgery in birds. Top to bottom: monopolar sling, scissor, grasping forceps, bipolar forceps for coagulations, trocars.
Figure 24.5a. The Teflon tube of the flexible needle is an excellent tool for the endoscopic-guided application of medicine directly to lesions such as this air sac granuloma.
Figure 24.5b. The flexible needle can be used for aspiration, biopsies, penetrations and application of medicine. Here, it is ready to penetrate a granuloma for a needle aspirate.
Preparation and Contraindications
Duration of pre-endoscopic fasting will parallel that of presurgical fasting for similar procedures. Longer fasts may be required to facilitate visualization of abdominal organs. General anesthetic techniques and requirements are discussed in Chapter 33, Updates in Anesthesia and Monitoring.
Birds with bleeding dyscrasias are at heightened surgical risk, especially when an organ biopsy is performed. The presence of cystic structures within the coelom, organomegaly or the presence of any fluid will complicate the procedure and increase the risk to the patient. Fluid should be carefully drained or reduced with diuretics prior to endoscopy. Obesity often reduces the view in the body cavity, increasing the risk of organ damage.
Coelomic Laparoscopy Studies
Left Lateral Approach
The endoscopic approach to the coelomic cavity depends on the diagnostic goal of the procedure (Fig. 24.6) and the results of previous imaging studies. The approach caudal to the last rib is ideal for exploration of the entire coelom (Fig. 24.7). Due to the presence of an ovary in most avian species on only the left side, approach from the left is generally utilized to allow visualization of female reproductive structures (see the section on gonads later in this chapter). The anesthetized bird is placed on its right side, with the left wing extended dorso cranially. The left leg may be pulled either cranially or caudally. The following description is for the approach with the leg extended caudally (Fig. 24.8).
Figure 24.6. The various endoscopic entry sites overlying the artist’s rendition of bones with colored areas representing the various air sacs encountered in endoscopy. Blue represents the intraclavicular, yellow the cranial thoracic, green the caudal thoracic and orange the abdominal air sacs. (M. Lierz, modified by Michael Pees).
Figure 24.7. An artist’s rendition of the organs encountered in endoscopy from the left lateral aspect. 1) heart 2) liver 3) trachea and lungs 4) proventriculus 5) ventriculus 6) intestines 7) kidney 8) spleen 9) adrenal-gonad area. The red star is a typical entry location. (M. Lierz, modified by Michael Pees).
Figure 24.8. Right lateral recumbency, left leg caudal. This bird is malpositioned; not being in a true lateral, which is critical for organ relationships. Secondly, it can be seen that in this blue crowned conure the area in front of the leg has a thick fat pad (arrow) that has to be penetrated to reach the musculature. (Greg J. Harrison).
Orientation to the surgical site is provided in Fig. 24.9-Fig. 24.11. A small incision is made in the skin, followed by a caudal reflection of the muscle layers with curved forceps. Penetration into the air sac is accompanied by a palpable and sometimes audible pop. The use of blunt instruments for this penetration cannot be overemphasized. Sharp instruments may damage underlying tissue. The caudal thoracic air sac is most often penetrated, however, the abdominal or cranial thoracic air sacs also may be entered (Fig. 24.12a,b). Some clinicians prefer to enter between the ribs. This is best accomplished by using a curved mosquito hemostat to elevate the ribs prior to penetration. However, using this technique the intercostal muscle is damaged, which is a disadvantage. The direction of penetration should be toward the cranial rib (remaining laterally positioned) to avoid the liver. The scope is stabilized with the tips of the forefinger and thumb while the hand rests on the table (Fig. 24.13).
Figure 24.9. The middle of a triangle formed by the spine (1), m. iliotibialis (2) and last rib (3); the red arrow represents the most common lateral point of entry for laparoscopy. (M. Lierz, modified by Michael Pees).
Figure 24.10. The muscle iliotibialis (a) overlies the point of entry, demonstrated on a dead bird with skin removed.
Figure 24.11. Using a curved forceps, the m. iliotibialis (a) is reflected caudally and the underlying fascia is penetrated caudal to the last rib (b), as is demonstrated here on a dead bird with skin removed.
Figure 24.12a,b. Entering the body cavity caudal to the last rib usually places the scope into the caudal thoracic air sac (b). Changing the route of penetration slightly, the scope is guided into the abdominal air sac (c) where the kidney (a) is located. One must penetrate the confluent wall of the medial aspect of the caudal thoracic air sac and the left lateral wall of the abdominal air sac.
Figure 24.13. Correct anchoring of the tip of the scope. The hand should always be in contact with the bird while the wrist is rested on the table.
The scope is advanced between the legs of the forceps. The air sacs will then be visible. Clear air sacs allow visualization of the gonad, the adrenal gland, and the cranial division of the kidney, through the abdominal air sac (Fig. 24.14). Cranial to this triad is the left lung. In larger birds, the scope may be advanced through the ostium between the lung and air sac to examine the bronchi (Fig. 24.15-Fig. 24.17). The medial lung, heart and liver can be seen as the scope advances cranially into the cranial thoracic air sac.
Figure 24.14. View into the abdominal air sac. Kidney (a), ovary (b), intestine (c), adrenal gland (d), ureter and oviduct (e).
Figure 24.15. The opening from the caudal thoracic air sac into the lung (aperta) allows retrograde endoscopy of internal structures of the lung.
Figure 24.16. Lung tissue viewed from the caudal thoracic air sac. The bronchi and lung parenchyma are clearly visible.
Figure 24.17. The endoscope has been advanced into the horizontal secondary bronchi that branches from the left or right primary bronchi. The honeycomb structure of the lungs is seen. This view cannot be appreciated via the trachea due to the diameter restrictions of the syrinx, the fragility of the primary bronchi and the acute angle at the origin of the secondary bronchi.
The ureter, uterus, and ductus deferens are seen ventral to the kidney, and intestinal loops come into view if the scope is directed ventrally from the original entry site. The proventriculus/ventriculus, liver and often the spleen may be visualized when the scope is directed cranioventrally. The punctured air sacs close rapidly and heal uneventfully. The skin incision can be closed with sutures or tissue glue.
A similar approach to the coelom is made by entering caudal to the pelvic limb, which is pulled cranially. The incision is made caudal to the last rib. With this approach, there is less chance of entering the cranial thoracic air sac.
Ventral Midline Approach
The bird is positioned in dorsal recumbency and a ventral midline approach to the coelom is made. A layer of fat may be present just under the linea alba in the area directly caudal to the sternum. Care must be taken on smaller birds not to inadvertently penetrate the duodenum or pancreas. The duodenum, pancreas and central liver can be examined from this approach.
Normally the air sacs are transparent, although a few vessels may be present (Fig. 24.18). Fatty infiltrates may be noted during routine examination without associated pathology. Opacity and small vessels in the wall of an air sac are early signs of inflammation (Fig 24.19). Other abnormalities of the air sacs include increased vascularity, thickened walls and granulomas (Fig. 24.20). These changes may be due to infectious processes, or to inhalation of respiratory irritants (ie, smoke, volatile chemicals). In some cases, a definitive diagnosis can be made from visualization, cytology and/or biopsy of air sac lesions (Fig. 24.21a-Fig. 24.21c). Removal or debulking such lesions has been described using laser and radiosurgery via the endoscope.
Figure 24.18. The ideal air sac is transparent. Minor blood and lymph vessels are commonly visible in pet and aviary birds.
Figure 24.19. Prominent vessels in the air sac, opacity or small granulomas are signs of infections and/or irritation from environmental contaminants (smoke, volatile chemicals).
Figure 24.20. Granulomas are forming in this case of air sacculitis.
Figure 24.21a. Fruiting aspergilloma in the air sac. This presentation carries a guarded prognosis.
Figure 24.21b. Active aspergilloma in an air sac with fluid exudate.
Figure 24.21c. Removal of an old aspergilloma using a biopsy forceps.
Lungs and Bronchi
The lungs are dark pink with a prominent reticular pattern. Within the lungs, the anastomosis bronchi are visible (see Fig. 24.16, Fig. 24.17). Pneumonia will obscure the normally well-defined parenchymal pattern of the lung. A yellow discoloration of the lung tissue is often noted with pneumonia (Fig. 24.22). Anthracosis (focal black spots) is regularly found in birds from cities, industrial areas or the homes of smokers (Fig. 24.22). Bleeding from trauma can be diagnosed by endoscopic examination (Fig. 24.23).
Figure 24.22. Internal lung tissue of a bird with dyspnea, viewed from the caudal thoracic air sac. Yellow areas and the loss of the typical lung parenchyma are signs of pneumonia. A biopsy to aid in specific diagnosis and treatment is highly recommended. The black spots are soot (anthracosis) and can be found in birds from smokers or cities.
Figure 24.23. Post-traumatic hemorrhage of the lung.
Proventriculus, Ventriculus - Serosal Examination
The proventriculus is an elongated, usually white organ located in the ventral coelom, surrounded by the abdominal air sac and the liver. The surface appearance and size of the proventriculus are diagnostically important. An enlarged proventriculus with a glossy surface might indicate proventricular dilatation disease (PDD). Focal bleeding may indicate foreign bodies or infections. The ventriculus cannot always be visualized. In birds with a muscular ventriculus, abnormalities are seldom discernible endoscopically (see Chapter 26, Diagnostic Value of Necropsy).
The liver is a large organ of uniform brownish red color. The liver border tapers to an edge (Fig. 24.24). A rounded liver border is not normal and may indicate infection or hepatic lipidosis (Fig. 24.25). The liver color changes to yellow with fatty liver. Focal bleeding in the liver appears bright red, while hemosiderosis appears dark red that over time can turn black in color (Fig. 24.26). Multiple white foci represent necrosis, abscesses or neoplasia (Fig. 24.27, Fig. 24.28). Pseudomembranous infiltrates of the liver capsule and air sacs may also be due to infection, inflammation or neoplasia (Fig. 24.29). Liver biopsies offer very valuable diagnostic information (see Chapter 15, Evaluating and Treating the Liver).
Figure 24.24. The normal liver is a brown-red homogeneous color with a sharp border.
Figure 24.25. A rounded liver border indicates an enlarged liver. A liver biopsy is often indicated to identify the nature of the hepatomegaly.
Figure 24.26. Hematoma of the liver after trauma.
Figure 24.27. White-yellow spots on the liver, diagnosed as abscesses. Neoplasias have a similar appearance.
Figure 24.28. Diffuse necrosis of the liver (histomoniasis).
Figure 24.29. Yellow, caseated material present on the liver and air sac due to a bacterial infection.
Heart and Pericardium
The lateral approach through the caudal thoracic air sac into the cranial thoracic air sac allows the visualization of the heart and pericardium. Pericardial effusions can be drained utilizing this approach. The normal pericardium is transparent (Fig. 24.30a). A milky pericardium is the result of pericarditis. The presence of fat at the heart base and heart apex is normal. An absence of fat is a sign of starvation or chronic disease. The main heart vessels are visible at the heart base as thick white tubes with regular pulses (Fig. 24.30b). The cardiac nerve supply can be found emanating from the thoracic vertebrae.
Figure 24.30a. Liver (a), heart pericardium (b), heart fat (c), lung (d) as seen in a normal bird.
Figure 24.30b. The aorta branching into the carotid artery is seen lying between the costal musculature, the base of the heart and the returning jugular vein.
The avian kidney is divided into three divisions. The adrenal gland and gonad are present at the cranial pole of the kidney (Fig. 24.31). The ureter can be seen and, in most cases, traced to the cloaca. The kidney is brownred- orange. Star-shaped collecting tubules filled with urates are often visible on the surface. These structures become hidden in swollen kidneys (Fig. 24.32). Yellow to white deposits on the surface of the kidney are often uric acid crystals and may indicate renal gout (Fig. 24.33). These foci might occur due to dehydration as well. After rehydration the foci are eliminated, while in the case of gout the foci are still present. Obesity can make the kidney appear diffusely yellow. Abscesses or cysts may appear as large yellow spots (Fig. 24.34, Fig. 24.35). Neoplasias or other gross abnormalities should be biopsied; assuming that the patient’s condition is sufficiently stable (see Chapter 16, Evaluating and Treating the Kidneys).
Figure 24.31. Kidney (a), adrenal gland (b) and testicle (c). Apart from the clearly visible testicles, the absence of a ligament crossing the cranial pole of the kidney represents a male bird. The lumpy nature of the kidney surface is normal for swans.
Figure 24.32. A swollen kidney as seen in acute nephritis. Note the lack of predominate stellate vasculature pattern associated with the renal glomeruli.
Figure 24.33. Uric acid deposits within the kidney. If this situation remains after several applications of intravenous fluids, renal gout is likely.
Figure 24.34. Renal cyst. Abscess or neoplasia are possible differential diagnoses.
Figure 24.35. Apart from the color changes of this kidney (K), multiple yellow foci are visible. The typical renal structure is no longer detectable. Histological examination of a renal biopsy showed a pyelonephritis. The ovary (O) has many involuted follicles.
The left lateral approach is best for viewing gonads because hens generally lack a right ovary. Right ovaries may be present in juvenile birds, especially in accipiters. Gonads are present ventral to the cranial poles of the kidneys.
DNA methods are available for sexing most monomorphic avian species and are less invasive than surgically sexing. Endoscopic sexing has the advantage of allowing direct visualization and evaluation of the gonads and other organs. Sexual function can be estimated and any damage from sterilization or castration can be observed. The normal appearance of the gonads varies between species. The right side should be examined if the gonads are not clearly observed or discernible as to either ovary or testes, or if presumed abnormalities are present. Gonads increase in size during sexual activity (Fig. 24.36-Fig. 24.38). Gonads can be small due to stress, malnutrition, lack of nesting stimuli or immaturity.
Figure 24.36. In juvenile birds, the rudimentary ovary on the right side still might be visible, sometimes showing single follicles (arrow). The normal left ovary is at the 9 - 11 position.
Figure 24.37. Secondary or tertiary follicles dramatically increase in size during the reproduction cycle. Pathological alterations such as inflammation or neoplasias might lead to similar findings. A detailed anamnesis indicating sexual display behavior may indicate an active ovary. If a large follicle is very close to the tip of the endoscope, the follicle can be easily confused with a testicle.
Figure 24.38. A cluster of follicles makes identification of the ovary (a) easy. More important is the detection of the suspensory ligament (b) of the ovary. It crosses the cranial pole of the kidney. Apart from sexing, evaluation of the ligament is important to judge the possible breeding performance of the bird. Adrenal gland (c).
The ligamentum dorsale oviductus (suspensory ligament) from the ovary crosses the cranial pole of the kidney coursing toward the uterus (Fig. 24.38). Lacking visualization of a well-defined gonad, this ligament is the main evidence for sexing the bird as a female. The ovaries can be difficult to detect in juvenile birds (Fig. 24.39). When examining breeding birds this ligament must be carefully assessed. In cases where this ligament is damaged or absent, the breeding performance of the bird is questionable (Fig. 24.40). If this ligament is cut in juvenile birds, they will not lay eggs. A large uterus may indicate previous egg laying or pathology. Inactive ovaries may be flat with a cobblestone appearance, while active ovaries may appear as a cluster of spheres. The size and number of visible follicles will vary with the age and reproductive status of the hen. Immature ovaries are sometimes difficult to distinguish from testicles. The ovary is generally an off-white, yellowish color, but pigmentation (usually black) occurs in some species (Fig. 24.41). In addition, the entire uterus should be evaluated.
Figure 24.39. In juvenile birds, the ovary (a) might be difficult to detect. Only the suspensory ligament (c) at the cranial pole of the kidney (e) characterizes the female bird. Lung (d), adrenal (b). Small ovarian follicles are not an accurate estimation of age or reproductive ability.
Figure 24.40. The ovary (O) is clearly visible and the suspensory ligament is missing. This bird cannot be recommended for breeding. The kidney (K) has just been biopsied (arrow).
Figure 24.41. Some avian species have melanistic gonads, as is seen in this ovary.
In male birds there is no ligamentum dorsale oviductus (Fig. 24.42a and Fig. 24.42b). The paired testicles are normally oval shaped with one to three faint vessels crossing the surface. In birds with clear air sacs, both the left and right testicles may be visualized from the left lateral approach. In some species the testicles are pigmented (e.g., Cacatua, some macaws and wading birds). The torturous course of the ductus deferens makes it distinguishable from the ureter (Fig. 24.43). The size of the testicles, epididymides and ductus deferens vary with the species, size, age and breeding condition of the individual bird (Fig. 24.44). The breeding potential of a male bird normally cannot be assessed by visual observation of the male anatomy. If a reproductive problem is suspected, a testicular biopsy is suggested (Fig 24.45).
Figure 24.42a. The teste (1) is at the cranial pole of the kidney (2) and close to the adrenal gland (3).
Figure 24.42b. Both paired teste are pictured here. With increased size of the left testicle or opacity of air sacs, the right testicle may be obscured from view.
Figure 24.43. Ductus deferens (d) and ureter (U) in a sexually active male.
Figure 24.44. Epididymis (E) of a sexually active male.
Figure 24.45. A testicle (T) with a structural abnormality that would indicate the need for a biopsy. Kidney (K).
Adrenal glands vary in color, size and shape (see Fig. 24.42a). They may be confused with immature or inactive gonads. If the gonads are well-developed, the adrenal glands may be obscured. The adrenal glands are usually located immediately cranial to the gonads. Changes in size or increased vascularity of the adrenal glands may indicate stress or disease (Fig. 24.46).
Figure 24.46. Enlarged adrenal glands (a) appear in cases of stress or diseases. Juvenile ovary (b).
Visible pathologic changes of the intestinal serosal surface are uncommon. Coelomic filarial worms are a rare finding in captive bred psittacines, but are regularly seen in birds of prey (Fig. 24.47 and Fig. 24.48). The intestine has a smooth surface covered with many vessels. The generally redishgray color varies according to the intestinal fluid. White foci may be a sign of previous penetration by endoparasites. Both thinning and thickening of the intestinal wall are signs of enteritis. Thinning can be appreciated endoscopically from the visibility of intestinal contents. Necrosis of the intestine wall might be visible in cases of clostridiosis or coccidiosis. Enlarged ceca filled with caseous yellow material could indicate histomoniasis.
Figure 24.47. Serratospiculum sp. in the air sac in a falcon.
Figure 24.48. The same bird as Fig. 24.47 12 days after treatment with ivermectin. The dead worm can easily be confused with a bacterial infection.
The pancreas lies within the duodenal loop (Fig. 24.49). The pancreas is a white-yellow color with a homogeneous matrix. Color changes, glassy appearance or an uneven surface often accompany pathologies and may warrant biopsy (see Chapter 26, Diagnostic Value of Necropsy).
Figure 24.49. The pancreas (P) identified in the duodenal loop (D). The pancreas should have a homogeneous structure and color.
Psittacine spleens are round, purplish and often speckled (Fig. 24.50). The spleen is located at the dorsal aspect of the proventricular/ventricular junction on the right side from a left lateral approach. Splenomegaly (immune response), yellow appearance (fatty spleen) and multiple white foci (necrosis) are possible pathological alterations (Fig. 24.51, Fig. 24.52). Chlamydophilosis and other bacterial diseases would be included in the differential. The spleen can be biopsied utilizing the same precautions as in mammals.
Figure 24.50. Using the left lateral approach, the spleen (a) is accessible from the abdominal air sac by pushing the proventriculus in the caudal-ventral direction to expose the right side of the proventriculus. The psittacine spleen is round and similar in color (redbrown) to the kidney and liver. Intestine (b).
Figure 24.51. Enlarged spleen of a bird with psittacosis.
Figure 24.52. Pale color changes and enlargement of a spleen.
Trachea and Thyroid Gland
The trachea and thyroid gland can be approached via the cervical branch of the cervicocephalic air sac, the clavicular air sac or through the coelomic cavity. The thyroid gland is visible as an elliptical pink structure attached to the trachea near the syrinx (Fig. 24.53). Alterations in size or a shiny appearance are considered abnormal and a biopsy may be indicated.
Figure 24.53. The thyroid gland on the carotid artery adjacent to the trachea as seen from the interclavicular air sac. A laparoscopic approach may be used by pushing the scope cranial, passing over the heart ventrally and following the trachea (a). The thyroid gland (b) can be visualized.
Endoscopic examination of the tracheal lumen is accomplished by extending the patient’s neck and gently advancing the scope through the larynx and down the trachea (Fig. 24.54). Unless the procedure is very rapid, an air sac breathing tube is necessary (see Chapter 33, Updates in Anesthesia and Monitoring). Many endoscopes are equipped with a protective sheath. Removal of this sheath will decrease the scope’s diameter and enable its introduction into the trachea of smaller birds. Unfortunately, this also increases the chance for damage to the endoscope. An unsheathed 1.2-mm scope can allow visualization of the trachea of birds the size of canaries and finches (Fig. 24.58). Without the sheath, the tracheal lumen can be examined, but no instruments can be introduced into the visual field in such a small patient. Evaluation should be made of the tracheal color, and mucosal texture. The mucosa of the trachea and the bronchi are light pink and glistening. The tracheal rings are clearly visible (Fig. 24.55a). In cases of tracheitis, the mucosa becomes red and swollen, making the rings less obvious (Fig. 24.55b). Tracheal exudates, when present, should be collected for cytology and culture. Possible abnormalities of the trachea include strictures, tumors, inflammation, parasites, fungal granulomas and foreign bodies (Fig. 24.56, Fig. 24.57). The tracheal diameter typically decreases toward the syrinx. The narrowed diameter and the tracheal bifurcation into the main stem bronchi make this area particularly prone to fungal granulomas and foreign bodies. Some degree of post-examination hyperemia of the trachea is normal.
Figure 24.54. Performing a tracheobronchoscopy. The neck of the bird must be fully extended. A beak speculum allows a better view and is safer for the scope in case the bird wakes up and attempts to bite the instrument. Anesthesia can be delivered via an air sac tube.
Figure 24.55a. Normal trachea.
Figure 24.55b. A case of severe tracheitis. The tracheal rings appear distorted due to the mucosal swelling, sloughing and hemorrhage.
Figure 24.56. Foreign body (seed) in a trachea. The mucosa is irritated and swollen.
Figure 24.57. Syngamus trachea in the trachea.
Acute dyspnea warrants endoscopic tracheal examination once the patient is stabilized. Hemorrhage of the tracheal mucosa may be seen with polytetrafluoroethylene toxicosis. More pronounced pathology would be expected in the lung parenchyma with this condition.
Respiratory parasites often can be visualized with the endoscope (Fig 24.57 and Fig 24.59). If mites are suspected and not visualized, swabbing the scope onto a sterile slide and examining the slide microscopically may reveal tracheal mites.
Figure 24.58. Endoscopy of a canary trachea with a 1.2 mm semiflexible endoscope [a]. (Greg J. Harrison).
Figure 24.59. A canary tracheal mite under 100x. This mite was obtained from the endoscope tip. The mites in the trachea were not visualized during endoscopy. (Greg J. Harrison).
Pharyngoscopy and Upper GI Studies
Sufficient anesthesia or restraint is necessary to prevent damage to the endoscope by the bird’s beak. In addition, the use of a beak speculum is advantageous. While under anesthesia, the bird is held in a ventral recumbency position and the neck is fully extended (Fig 24.61). This position allows endoscopic examination of the inner surface of the beak, oral cavity, choana, rhinal cavity, tongue and larynx. The shape of the tongue differs from species to species. The infundibular cleft should be free of swelling and debris. Check the entire oral cavity for signs of pathology (Table 24.7).
Figure 24.60. For upper digestive system endoscopy, one uses a sheath with a working channel, here with an endoscope inserted. Hollow organs can be insufflated and flushed using liquids. Tubes for infusion liquids can be attached to the liquid-in and liquid-out taps (a). The arrows demonstrate the direction of the flow of liquids. A port for flexible instruments (grasping biopsy forceps, needle, scissors or various brushes) (b) is shown above the viewing eyepiece.
Figure 24.61. When performing a gastroscopy, the head of the bird must be in a position lower than the body. Aspiration of liquids into the lungs is then easier to avoid. Tracheal intubation of the bird during anesthesia aids in the prevention of aspiration.
Table 24.7. Common Oral Pathology in Psittacines
The rhinal cavity can be entered from the choana and the turbinates examined. The operculum prevents the passage of a scope through the nares. The points used to perform an infraorbital flushing technique also can be entered endoscopically.
Esophagus, Crop, Proventriculus, Ventriculus - Mucosal Examination
Examination of the esophagus, crop and proventriculus via the oral cavity is a common procedure (Fig 24.62). As the esophagus, crop (Fig 24.63) and proventriculus are hollow organs, insufflation is necessary for visualization.
Figure 24.62. Normal esophagus of a chicken.
Figure 24.63. Endoscopic view at the entrance of the crop in a chicken. The oblong structure is the wall between the esophagus and the crop. The other opening is the entrance to the crop.
Prior to gastroscopy, a fasting period is important to allow maximum viewing without the presence of food. Insufflation with air or sterile fluids is commonly used for positioning and advancement of the endoscope. Sterile fluids allow the flushing out of debris and subsequent dilation of the GI tract. This greatly aids in visualization. It is important that the fluid be warm to the touch to avoid decreasing the body temperature of the bird. A working channel is necessary to aim the washing solution. This working channel should have two taps, one for fluids in and one for fluids out (see Fig 24.60). The third port is ideal to allow simultaneous passage of a biopsy or grasping forceps. The fluid inlet is attached to an infusion bag or bottle positioned at a higher elevation. A larger infusion tube is connected to the fluid outlet leading to a collecting container. The two taps allow accurate control of the amount of fluid within the digestive system, expanding the organs as needed for examination. The fluid outlet is closed and the selected portion of the GI tract is dilated until good visualization of the mucosa is achieved. The fluid outlet is then opened in order to flush out mucus and small particles. Opening the fluid inlet again can increase the pressure. To avoid aspiration, fluid should not be allowed to exit the digestive tract through the oral cavity, which could and often does lead to the contents being inhaled. Occlusion of the scope and esophagus to retain the infused air or fluid in the crop can be easily accomplished by placement of digital pressure on the scope and esophagus. Although the tracheal rings are solid in birds, caution should be used to prevent restriction of normal airflow. In addition, the bird should be positioned in ventral recumbency with the head lower than the body. An endotracheal tube should be in place (Fig 24.61).
The mucosal surfaces of the esophagus and the crop vary between species. The mucous membranes of the esophagus, crop and proventriculus are a homogeneous pink (Fig 24.62). The mucosa of the esophagus is usually smooth; the crop has furrows and the proventriculus papillae (Fig 24.63). Focal dark red or bleeding areas are signs of irritation, which can be due to foreign bodies, infections, ulcerations, or neoplasia. A yellow coating of the mucosa can be seen with trichomoniasis, candidiasis, the diphtheric form of avian pox or vitamin A deficiency or excess. If there is a loss of the proventricular mucous membrane’s normal color it might be a sign of a wall suggesting PDD. Biopsy of the proventriculus or the crop and submission for histopathology may confirm a suspected diagnosis of PDD. However the significant risk of dehesience must be considered prior to obtaining a proventricular biopsy. To evaluate the proventriculus in larger psittacines, it may be necessary to introduce the scope through an ingluviotomy incision. A preferred location for this incision is to the left and somewhat dorsally, to avoid postoperative pressure on the crop incision from ingesta. An area of reduced vascularity is ideal. The scope is introduced and advanced carefully into the thoracic esophagus, continuing caudally to the proventricular lumen. This procedure is useful for proventricular biopsies and retrieval of foreign bodies. A flexible scope is mandatory to evaluate a fragile proventriculus (e.g., normal lories, large macaws and all cases of PDD) or all ventriculi.
The endoscope simplifies cloacal examination. Insufflation is necessary for viewing to maintain an adequate distance between the scope and tissues under examination. A soft rubber feeding tube may be used, with digital pressure applied around the scope barrel to retain the air or fluid.
When performing a cloacoscopy, the bird is placed in dorsal recumbency and the endoscope is inserted with its working channel. Insufflation is usually done using fluid (see description at Esophagus, Crop, Proventriculus, Ventriculus - Mucosal Examination, above). Feces and urine are almost always present and should be washed out for optimal visualization. The mucosal surface is pink with ureteral papillae (Fig 24.64). Urine can be seen emanating from these ostia of the ureters (Fig 24.65). Hyperemic cloacal membranes are indicative of inflammation or infections. Rough and red raised areas (cauliflower shape) are suggestive of papillomatosis. Inside the cloaca, the openings of the ureters, the rectum and, in female birds, the uterus can be viewed. The oviduct can sometimes be entered and the caudal chambers investigated. The occurrence of fresh blood within the feces is a clinical indication for cloacoscopy, as it may originate from the cloaca, the intestine, the ureters or the uterus.
Figure 24.64. Psittacine cloacal mucosa visualized using liquid insufflation.
Figure 24.65. Urates (a) emanating from an ureter on the cloacal surface.
In most species, feathers conceal the opening of the ear canal. The external orifice can vary from <2 mm in small species and up to 6 cm in some large raptors. The normal tympanic membrane is clear and slightly convex. Otitis externa is not a common finding in psittacines, but bacterial, fungal, neoplastic and allergic conditions may occur. In raptors, common findings are bleeding into the ear canal from head trauma.
The nerves of the brachial plexus are seen anterior and lateral to the heart (Fig 24.66a) The sacral pluxus sometimes visible dorsal to the kidney (see Fig 24.66b). Ed Note: Harrison has used endoscopy to evaluate nerve damage. Muscles, nerves, vessels, tendons and ligaments can be examined using the endoscope. In cases of trauma, air or fluids can be injected subcutaneously to provide a path for the scope to follow anatomical structures into the area of trauma. This technique could be useful to investigate brachial plexus evulsion, nerve transection, thrombi, emboli, and traumatic damage to soft tissue.
Figure 24.66a. The brachial plexus is visible craniallateral to the heart.
Figure 24.66b. Plexus sacralis dorsal to the kidney.
Coordinating the endoscope and the biopsy instrument can be challenging. The advent of sheaths that are now provided with many endoscopes has simplified this procedure by allowing the biopsy forceps to approach the site without changing the field of vision. The small size of the biopsy forceps used for these procedures usually precludes serious hemorrhage. Endoscopic-guided biopsies allow sampling of organs under direct visualization (Fig 24.67). In general, biopsies of the lung, air sac, liver, kidney, spleen, gonads, proventriculus, ventriculus, thyroid gland and mucosal membranes of esophagus, crop and cloaca are possible using a biopsy forceps within a working channel. Aspiration biopsies are possible using a long, flexible needle with a Teflon cover (see Table 24.6). Puncture of cysts, bone marrow biopsies or lavage sampling are the ideal uses for this needle. In case of a general alteration of an organ, the biopsy should be taken from the organ’s border (Fig 24.68). Contraindications of biopsies are similar to those mentioned for endoscopy. Endoscopic procedures, in particular tissue biopsies, lead to changes in certain blood values ; therefore, planned blood sampling must be performed before endoscopy.
Figure 24.67. In case of a pansystemic airsacculitis (here milky), the entrance of the scope is the site of choice for a biopsy.
Figure 24.68. In case of a grossly abnormal liver, a biopsy should be performed at the liver border.
Endoscopic-guided Surgical Procedures
Endoscopic-guided sterilization or castration is possible. This might be indicated in chronic egg laying or birds that are aggressive during breeding season. As castration is quite complex, sterilization represents a quick and easy procedure, as the gonads need not be removed. This can be accomplished using electrosurgery with a bipolar endoscopic forceps (Fig 24.69a and Fig 24.69b). Performing this procedure when the bird is sexually inactive reduces the risk of hemorrhage. (Sterilization may hormonally influence behaviors). In juvenile or hormonally inactive females the challenge one is faced with is making the distinction between the ureter and the quiescent oviduct. The ureter is marked by urates, or its regularly occurring contractions (Fig 24.70). Administering intravenous fluids will increase the likelihood of seeing urates pass down the ureter.
Figure 24.69a. For sterilization of the female bird, the oviduct can be obliterated using a bipolar coagulation forceps. Surrounding tissues must be avoided.
Figure 24.69b. The appearance of the coagulated section of the oviduct that will scar closed.
Figure 24.70. The dichotomy of when to perform female reproductive surgery is amply demonstrated on the immature or involuted side of the question by observing the intimate proximity of the ureter (a) to the uterus (b) in this example. Avoiding collateral damage is imperative. The ureter should be observed for movement of urates (arrows) seen moving during regular contraction cycles. While on the opposite end of the spectrum, the mature or active uterus has up to a centimeter of distance between these structures in a bird as small as a cockatiel, allowing almost no chance for neighboring tissue damage; hemostasis is the challenge. Vessels increase in length but more significantly in diameter and thickness, creating the imminent danger of life-threatening hemorrhage. Some of these vessels are too large for casual coagulation or less than ideal vessel-clamping techniques, resulting in oozing in the first case or loss of the clip and hemorrhage in the latter.
Endoscopic-guided obliteration of air sac granulomas or papillomas in the cloaca is possible. Endoscopic-guided laser diodes have been used to obliterate granulomas within the trachea or air sac. Multiple-entry endoscopic surgery has been developed for resection of tumors or castrations (Fig 24.71). Instruments are guided into the endoscopic field of vision using trocars. Laser or radiosurgery is helpful to maintain hemostasis.
Figure 24.71. Endoscopic-guided multiple entry for bipolar radiosurgery castration.
Complication During and After Endoscopy
Hemorrhage is the main complication arising from endoscopy. The kidney can be damaged during penetration of the air sac at the beginning of the laparoscopy. Perforations of the proventriculus may result in fatal peritonitis. If major bleeding occurs, electrocoagulation, oxidized regenerated cellulose or sterile sticks of cotton wool can be used. The bird should be placed at a 45° angle with the head elevated to prevent blood from entering the lungs. This keeps the blood in the caudal air sacs. If a large entry site has been created, the site may need deep sutures to close the muscles and prevent subcutaneous emphysema. Postsurgical closure of air sac defects is usually not necessary. If emphysema occurs, it should be punctured and deflated regularly until these defects close themselves. When performing endoscopy on multiple subjects sufficient sterilization time for the equipment is imperative to avoid transmission of disease.
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Affiliation of the authors at the time of publication
Institute for Poultry Diseases, University of Berlin, Berlin,