Rectovaginal fistula are a rare congenital disease of dogs characterized by communication between the dorsal wall of the vagina and the ventral portion of the rectum.
This condition may also develop as an acquired secondary complication following dehiscence during colorectal surgery.
Congenital rectovaginal fistula result in the vulva functioning as a common opening to the urogenital and gastrointestinal tracts. Usually, the abnormality is associated with type II atresia ani, in which the rectum ends as a blind pouch immediately cranial to the imperforated anus.
The prevalence has not been totally determined, but apparently it is more common in dogs than cats.
Clinical signs include passage of feces through the vulva, vulvar irritation, tenesmus, cystitis, and megacolon, among others. However, some of these signs will not be evident while the dog is on liquid diet.
Diagnosis is based on history, clinical signs, and physical examination. Radiographic examination with contrast medium infused through the vagina or fistula may be useful for determining the position of the fistula and terminal rectum.
Two surgical techniques are frequently used in the treatment of rectovaginal fistula and atresia ani: in one the fistula is isolated, transected, and the rectum and vulvar defects are closed separately, followed by reconstruction of the anus. In the other, the rectum is transected cranial to the fistulous opening, the affected segment is removed, and the terminal part of the rectum is sutured to the anus. Closing the rectovaginal fistula by numerous purse-string sutures along its length and the use of plastic adhesive in the treatment of rectovaginal fistula induced experimentally have also been reported. Recently, two dogs were treated successfully by a technique that preserves the fistula and uses it in the surgical reconstruction of the anal canal and anus.
Among the reported complications following surgery, fecal incontinence is one of the most important. This sequela may be associated with lack of function, possible absence of the external anal sphincter, or nerve damage during the surgical procedure.
Other possible complications include obstipation and tenesmus, constipation, megacolon, anal gland odor, edema of the anal area, rectal prolapse, urinary incontinence, anal stenosis, and wound dehiscence.
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