ETIOLOGY

In the United States and other developed nations, VVFs occur as a result of surgical trauma, most commonly at the time of abdominal or vaginal hysterectomy. Unrecognized suture placement into the bladder during closure of the vaginal cuff results in tissue necrosis and subsequent fistula formation. Excessive blunt dissection of the bladder can result in ischemia or an unrecognized tear in the posterior bladder wall. Approximately 75% of VVFs are reported to occur after hysterectomy for benign disease.⁴ The incidence of VVF after hysterectomy is between 0.5% and 1%.⁵ VVFs also occur after anterior colporrhaphy, sling procedures for stress incontinence, cystocele repair, colposuspension procedures, and urethral or bladder diverticulectomy. Approximately 90% of VVFs in North America result from gynecologic procedures. The other 10% are caused by advanced local malignancy (i.e., cervical, vaginal, and endometrial), radiation therapy, inflammatory bowel disease, foreign bodies, and infectious processes of the urinary tract.

PREVENTION

Recognizing that most VVFs are iatrogenic, it is paramount that the treating surgeon takes the necessary precautions to prevent their occurrence. Risk factors reported for fistula development include prior cesarean section, endometriosis, previous cervical conization, and radiation treatment.⁶ The bladder is most often injured during the dissection of the posterior bladder wall from the anterior surface of the uterus at the level of the vaginal cuff during abdominal hysterectomy. Placement of an indwelling Foley catheter and meticulous sharp dissection can minimize inadvertent injury. Iatrogenic injuries can be unavoidable in difficult reoperations and in patients with dense adhesions that obliterate normal surgical planes. Careful attention should be paid to diagnose and repair the injury intraoperatively. Filling the Foley catheter with methylene blue dye to check for leakage is a simple and effective method of checking bladder integrity. If a bladder injury is recognized, two-layer repair is required after adequate exposure is provided. A drain should be placed. The catheter should be left in longer than the usual 1 or 2 days after hysterectomy. An interposition flap can provide an additional layer of coverage.

DIAGNOSIS

History

Patients typically present with continuous urinary drainage (day and night) from the vagina after gynecologic or pelvic surgery. Any patient with urinary incontinence immediately after pelvic surgery should be evaluated to rule out a VVF. The fistula may manifest immediately postoperatively, but it often becomes clinically apparent days to weeks later. Ureterovaginal fistulas tend to manifest later than VVFs. Ten percent of patients with a VVF have an associated ureterovaginal fistula.⁷ Early in the postoperative course, patients may present with fevers, abdominal pain, hematuria, ileus, and lower urinary tract symptoms.

Patients with VVF related to prior radiation therapy may present 6 months to 20 years later.⁸ Fluid draining from the vagina may be urine, lymph, peritoneal fluid, fallopian tube fluid, or vaginal secretions. Important considerations in the differential diagnosis of VVF include urethrovaginal fistula, ureterovaginal fistula, ectopic ureter, peritoneal fluid drainage, and vaginal cuff infection.

Diagnostic Tests

To confirm that the leaking fluid from the vagina is urine, the fluid can be sent for creatinine analysis. Elevated levels (relative to serum) establish the diagnosis of a communication between the vagina and urinary tract. Physical examination is paramount in the evaluation of a woman with a suspected fistula. The diameter, depth, mobility, and mucosa of the vagina must all be assessed. Concomitant prolapse, urethral hypermobility, and stress incontinence should also be evaluated. Vaginal examination with a speculum can isolate the point of leakage. The most common location for VVF (after a hysterectomy) is at the level of the vaginal cuff. Pooling of urine at the apex and the fornices is commonly seen. Surrounding vaginal mucosa may appear edematous and erythematous, making it difficult to identify the opening. Placing a Foley catheter into the bladder can assist by visualizing the balloon. If all of these measures fail to identify a fistula, dye tests can be used for confirmation. Instilling methylene blue dye through the Foley catheter, with concomitant inspection of the vagina for leakage of blue fluid, can help identify a VVF. Requesting the patient to ambulate with a vaginal pack in place may stain the packing blue. If a VVF is still not identified, the patient should be given oral phenazopyridine, which stains the urine orange. The vagina is then packed, and orange staining confirms a fistula. A positive phenazopyridine test result with a negative methylene blue test result strongly suggests a ureterovaginal fistula.

All patients with a diagnosis of a urinary fistula should undergo upper tract evaluation and cystoscopy. Upper tract evaluation can be done with intravenous pyelography (IVU) or retrograde pyelography. Ureteral involvement can be demonstrated by hydronephrosis or extravasation on IVU, although the ipsilateral kidney can appear normal with prompt drainage. Retrograde pyelography remains the most sensitive test to evaluate ureteral involvement in the presence or absence of a VVF. Cystoscopy should identify the location and size of the fistula and determine its relation to the ureteral orifices. It is important to ascertain that there is adequate bladder capacity and to rule out foreign body as the source of the fistula. Surveillance for multiple fistulas is imperative, because this finding would alter operative repair. Patients with a radiation- or malignancy-associated fistula must undergo biopsy of the site before repair. A voiding cystourethrogram (VCUG) can help identify the presence and location of a fistula. Coexisting vesicoureteral reflux, urethral diverticulum, stress incontinence, and cystocele can also be identified, which may alter the surgical plan. VCUG can help elucidate fistulas involving the rectum or uterus, and vaginoscopy can assist in identifying the vaginal communication.

TREATMENT

Conservative Management

Small VVFs may close spontaneously with continuous Foley catheter drainage (up to 10% of cases). This has usually been attempted by the time patients have sought consultation with a specialist. Three weeks of drainage is a reasonable option if the fistula is discovered early in the postoperative period. Mature fistula tracts are unlikely to resolve with this technique. Prolonged catheter drainage requires coverage with antibiotics.

Another conservative treatment option includes fulgurating the lining of the fistula tract. This should not be attempted with large fistulous tracts. Stovsky and colleagues ⁹ reported closure in 11 of 17 patients with fulguration of fistulas less than 3 mm long and with 2 weeks of catheter drainage. Reports have shown success with fibrin therapy in treating small VVFs.¹⁰ Most conservative measures ultimately fail in the attempt to cure VVFs. For larger, complex, and radiation-induced fistulas, there is no role for conservative treatment, and formal repair remains the gold standard.

Operative Management

Preoperative Considerations

Before formal repair of a VVF, many factors must be considered to optimize the chances of a successful repair. Historically, most surgeons advocated waiting 3 to 6 months before surgical repair to allow the fistula to completely mature.^11,¹² They theorized that this allowed maximal healing during the post-hysterectomy inflammatory stage. However, patients with VVFs experience enormous social, physical, and psychological stress during this period that greatly hinders their quality of life. Contemporary surgeons have reported excellent results with early repair, and the strategy avoided patients’ distress throughout a waiting period.^13,¹⁴ Typically, early transvaginal repair is performed 2 to 3 weeks after the time of injury. This is most commonly done in women with fistulas that form after hysterectomy using an abdominal approach. Patients with vaginal cuff infections or pelvic abscesses must be treated long-term with antibiotics before any repair attempt. Patients with previously failed repairs or radiation-related fistulas are not candidates for early intervention. They should wait a minimum of several months before repair. VVFs after traumatic delivery are ischemic in origin and require a longer period of conservative management.

The most appropriate approach to formal surgical repair of a VVF is the one most familiar to the surgeon. The choice between an abdominal or vaginal approach depends on the surgeon’s experience, training, and comfort level with the procedure. The highest success rates are associated with the first operation, regardless of the approach. Traditionally, the fistula’s location dictated the surgical approach. Infratrigonal and bladder neck fistulas were repaired vaginally, whereas supratrigonal fistulas were repaired transabdominally. Even complex high VVFs can be repaired using a transvaginal approach with adherence to good surgical technique and tissue interposition. The advantage of an abdominal approach is the ability to perform simultaneous procedures for coexisting intra-abdominal pathology, including augmentation cystoplasty, ureteral reimplantation, and repair of bowel fistulas. The vaginal approach avoids an abdominal incision and possible bladder bivalving. It is associated with decreased morbidity, shorter hospital stay, and quicker patient convalescence. We use the transvaginal approach for most VVFs.

Many principles are integral to fistula repair, regardless of the approach chosen. Excellent exposure with watertight, tension-free closure using multiple, nonoverlapping sutures lines provide an approximately 90% chance of cure on the first attempt. Continuous catheter drainage postoperatively is mandatory. Interpositional grafts optimize the chance for cure if the integrity of the repair is in question.

Preoperative preparation includes prescribing antibiotics to clear any infection and provide a sterile environment for repair. Urine culture should document absence of infection before surgery. Broad-spectrum, intravenous antibiotics are provided preoperatively. Preoperative estrogen-containing vaginal cream is used in the postmenopausal or post-hysterectomy patient to improve the quality of the vaginal tissues.

Traditional repair of VVF included excision of the tract to provide clean and vascular edges. This was thought to increase chances for cure. Raz and associates ^15,¹⁶ demonstrated excellent results without excising the fistulous tract with no adverse effects. Excising the fistula enlarges the tract, and it may cause iatrogenic bleeding, requiring hemostatic measures that may inhibit healing. Excising fistulous tracts located near the ureteral orifices may require ureteral reimplantation.

Before surgical repair, the surgeon should be familiar with several techniques for interposition of tissue. Although these grafts are often necessary in large, complex, post-radiation, and failed primary repairs, it is difficult to accurately predict which fistulas will require the additional layer of coverage to avoid a tenuous repair.

Preoperative evaluation should attempt to identify patients who have coexisting stress urinary incontinence. Simultaneous sling procedure or bladder neck suspension can be performed, avoiding the need for a second procedure. Concomitant repair for stress incontinence does not increase the fistula recurrence rate.¹⁷ It is also important to consider the sexual function of the patient and ensure preservation of vaginal depth in the sexually active patient. This can require rotational flaps in patients with large fistulas and vaginal stenosis. Local estrogen replacement should be used in patients with vaginal atrophy.