Wednesday, July 1, 2009
An anovaginal fistula is an abnormal communication between the vaginal vault and the anal canal and/or low rectum. There are few diagnoses that cause as much psychological distress and embarassment as an anovaginal fistula. Women present with frequent urinary tract infections, passage of stool when they urinate, and foul smelling, feculent vaginal discharge. Often, there is also a concommitant sphincter injury resulting in fecal incontinence. Patients who suffer from this malady often do not seek medical treatment for years because of the humiliation. Social interactions are compromised. It's a horrible existence.
Anovaginal fistulae are caused by childbirth injuries (such as occur after an episiotomy), cryptoglandular perianal abscesses, Crohn's disease, and malignancies. It's important to define the anatomy prior to definitive treatment. A high rectovaginal fistula (several centimeters above the dentate line in the proximal rectum) usually requires an intra abdominal surgical approach with at least a partial proctectomy. Lower rectovaginal and most anovaginal fistulae are usually more amenable to a transanal approach.
In the CT above, you can see the contrast extravasating from the anal canal to the more anterior vagina (note the thin slip of "white" that connects the two structures). This poor older lady had been suffering from increasingly more debilitating symptoms for years. She hated going out in public. She avoided lunches with her little old lady friends. She kept getting these awful urinary tract infections.
The fistula was easily palpable on digital rectal exam. But I sent her for colonoscopy, CT scan, and cystoscopy to rule out the possibility of an underlying malignancy. The most important factor in determining the optimal surgical approach is assessing the patient's level of continence. An incontinent patient needs a sphincteroplasty in addition to repair of the defect. Fortunately this lady had good sphincter tone.
My approach to a low anovaginal fistula is via a transanal repair. Some OB/Gyns will repair these transvaginally but it makes more sense to me to address the hole from the side of maximal generated pressure. The fistula is identified and granulation tissue is curetted/debrided and then you simply imbricate the circular muscle with interrupted sutures to close it. Then I like to cover the repair with a transanal advancement flap of rectal submucosa/mucosa, mobilized from at least 4cm above the defect. Some have described using well vascularized muscle flaps (bulbocavernosus muscle---Martius flap) to reinforce the repair in cases where the tissues seem a little sketchy. This lady did fine, but long term cure rates run at about 80% for rectal advancement flap repairs....