Reconstructive Surgical Procedures to Enhance Mare Fertility

Reconstructive surgery of the caudal reproductive tract is commonly performed to restore or  maintain a mare’s future fertility. Common problems that practitioners may be faced with  include pneumovagina, urovagina, perineal lacerations, rectal-vaginal fistulas, and cervical tears.  Surgical correction of these problems can be performed and these surgeries are generally  performed standing. In most cases, standing sedation and possible epidural anesthesia is all that  is needed to perform most surgeries. Practitioners that have access to standing stocks and an  interest in surgery can perform many of these procedures in the field.  

In the following paragraphs, I will address some of the common problems practitioners may see.  I will describe various procedures used to correct these problems and my experience with them.  I will also discuss some mistakes I made and the techniques that I am presently using to repair or  enhance a mare’s fertility.  

Preparation of Standing Perineal Surgery  

The mare is restrained in standing stocks, and the tail is wrapped and elevated. Ensure you have  a quick release knot on the tail in case the mare does go down in the stocks. Depending on the  surgical procedure, the rectum is evacuated and the perineum, vagina, and rectum are cleaned.  Epidural anesthesia may be performed for some procedures (see below). Appropriate instruments  (long handle instruments) should be available, and a headlight is essential for many of these  procedures. Often the mare’s foal is present, so you may have to sedate both the mare and foal  during the procedure. I generally sedate the younger foals using either 50 to 100 mg of xylazine  (1.1 mg/kg, intravenously). The foal can also be confined to a small pen next to the head of the  mare.  

Methods of Providing Anesthesia for Surgery  

Local anesthesia can be achieved using local infiltration of either lidocaine or mepivacaine.  Local anesthesia can be used solely for some procedures or in addition to epidural anesthesia in  other procedures. The amount and location of administration of local anesthesia will often be  dictated by the procedure in questions. Generally 10 to 30 mLs of lidocaine or mepivacaine is  used.  

Epidural anesthesia is commonly used for surgery involving the mare’s caudal reproductive tract.  Numerous pharmaceutical methods of providing epidural anesthesia exist, and the type of  agents(s) used is often dependent on surgeon’s preference and the particular reason for the  epidural. Local anesthetics are often used in combination with alpha-2 adrenergic agonists. I  personally have always used a mepivacaine and xylazine hydrochloride combination mixed with either saline or sterile water. For a 450 kg mare, I will generally use 75 mg to 100 mg of  xylazine hydrochloride and 1.5 mLs or 2 mLs of mepivacaine mixed with 6 to 7 mLs of sterile  saline or sterile water. I use a “hanging drop” technique by placing a 1.5-inch, 18-gauge needle  through the last sacral vertebrae (S5) and first caudal vertebra (C1). A brief description of the  procedure is as follows: the site is clipped and aseptically prepped. Using sterile gloves, I will  palpate the dorsal spinous process of S5 and then use the epidural space located about 1 cm  caudal to this landmark on midline. Ensure the horse is standing squarely during the epidural  procedure. I insert the needle in a direction perpendicular to the skin. Once the needle is just  through the skin, I fill the hub of the needle with a small amount of epidural solution. The needle  is then advanced until the fluid in the hub is aspirated into the epidural space. The needle can  also be inserted between the first and second caudal vertebra. Elevating and lowering the tail  helps identify the movable articulation between the first and second caudal vertebrae.  

Pneumovagina  

Performing an episioplasty or Caslick’s procedure commonly treats pneumovagina. In certain  cases where there is atrophy or a laceration of the perineal body a perineal body reconstruction  procedure (Gadd Technique) can be performed.¹ A Gadd technique involves closure of the dorsal  vulva after two large triangular flaps of vestibular mucosa, which connect dorsally, have been  removed. Removal of the mucosal flaps can be performed using local anesthesia. The defect  created by removing the vestibular mucosa is then sutured closed to appose the dorsal aspect of  the vulva and decrease the surface area within the vestibule. The skin of the vulva is closed as  with the Caslick’s procedure. Perineal body reconstruction can be performed easily and  efficiently and carries a good prognosis.  

Urovagina/Urine Pooling  

This condition is primarily observed in older multiparous mares. Urovagina results from laxity  of ovarian and/or pelvic supporting ligaments due to age and repeated pregnancies.^1,2 Urovagina  can also result from poor pelvic conformation and body condition. The sagging of uterus into the  abdomen which occurs primarily during estrus when the uterus is edematous and under the  influence of estrogen will pull the vagina cranially and ventrally. The urethral orifice is pulled  forward and when urine is voided, some is refluxed cranially, causing vaginitis, cervicitis,  endometritis, and infertility. Some mares may initially pool urine in the vagina intermittently  and careful conservative management of breeding may be successful occasionally in these mares.  Clinical signs include infertility, urine scalding, and often these mares have a smell like  urine/ammonia. The diagnosis is either based on clinical signs or vaginal speculum exam. If the  urine pooling cannot be controlled medically then surgical intervention is recommended. In some  cases an endometrial biopsy is recommended prior to surgery to evaluate the endometrial tissue.  

Surgical correction of urine pooling is one of the most frustrating reproductive surgeries. The  urethroplasty procedure may be performed without problems, but the outcome is difficult to  predict. Surgical repair failure can result in fistula development. Fistula development results in  continued urine pooling and surgical closure of the fistula can be difficult to achieve. In many  cases the entire procedure should be repeated. 

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