Management of urovagina

Introduction

The conformation of the reproductive tract in most multiparous mares gradually changes with age to where the cranial aspect angles more ventrally. The downward tilting of the reproductive tract enables urine that is not completely voided to gain access to the cranial vagina. This can result in contamination and inflammation of the cranial vagina, cervix, and uterus, adversely affecting fertility. Urovagina or urine pooling, can be prevented by moving the exit hole for urine from the cranial to the caudal aspect of the vestibule, the urethral extension procedure. Other procedures used to prevent urovagina include the perineal body transection and the uteropexy. These two procedures have not worked as well to prevent urine pooling for mares in our practice as the urethral extension. Thus, this presentation addresses urethral extension procedures to prevent urovagina.

Prior to performing a urethral extension, it is important to determine that the urovagina is not just a transient postpartum event. Also, examine the skin below the vulva for scalding. If this is present, the mare most likely has an incompetent urethral sphincter, or possibly a bladder stone causing chronic leaking of urine. A lax urethral sphincter can be identified by digital palpation. A bladder stone is usually found on manual vaginal exam, rectal exam, or ultrasound exam. Both of these abnormalities can cause urine pooling, but urine pooling without these abnormalities, rarely causes scalding of skin below the vulva.

Urethral Extension

There have been a few techniques described to extend the urethra caudally. Monin (1972) described pulling the transverse fold caudally and suturing it to the ventrolateral walls of the vestibule. Brown (1978) described incising the transverse fold horizontally and continuing the incision along the left and right ventrolateral walls of the vestibule to the caudal aspect of the vestibule, followed by suturing the ventral edges together and then the dorsal edges together to create a long tunnel. McKinnon (1988) described making a similar incision across the transverse fold continuing with a more dorsal incision along the ventrolateral walls of the vestibule than the Brown technique. The ventral edges of mucosa are dissected away from the underlying tissue, then sutured together and to the transverse fold in an inverting 1-layer closure, resulting in a Y-shaped closure pattern. Dissection of the ventral edges away from the underlying tissue results in less tension on the suture line, but only a 1-layer closure. Another procedure was described in 1990, which used a similar incision as the Brown technique, but pulled the transverse fold as far caudally as possible to reduce tension on the cranial aspect of the repair, then the ventral and dorsal edges along the ventrolateral walls of the vagina were sutured together and to the transverse fold in 2-layers, resulting in a Y-shaped repair. I have found this latter technique, with modifications as needed to be the most successful.

In preparation for the urethral extension, the mare is sedated with xylazine and detomidine and placed in stocks. Infrequently, butorphanol is added. Epidural anesthesia is induced with xylazine (0.17mg/kg), lidocaine (0.22mg/kg), and saline (4ml). The tail is tied up and Balfour retractors are used to gain access to the vestibule. Repair of leaks or extension of a previously placed urethral extension can be done using local anesthesia.

The technique I use for the urethral extension depends on the conformation of the vestibule and the transverse fold. They all involve splitting the margins of the transverse fold and continuing the incision along the ventral walls of the vestibule caudally to just past the caudal brim of the pelvis. The transverse fold is retracted caudally, then the ventral edges are sutured together and the dorsal edges are sutured together, both using 3-0 polyglactin 910. [...]