What are the typical presentation, diagnostic work‑up, and definitive treatment options for a colovaginal fistula in an adult woman?

Colovaginal Fistula: Presentation, Diagnosis, and Treatment

Clinical Presentation

Women with colovaginal fistulas typically present with a characteristic triad: passage of stool or flatus through the vagina (89-95% of cases), foul-smelling vaginal discharge (68%), and a history of prior hysterectomy (95%). 1

Key presenting symptoms include:

• Passage of stool per vagina (89% of patients) 1
• Passage of flatus per vagina (37% of patients) 1
• Foul-smelling vaginal discharge or vaginitis resistant to treatment (68%) 1
• Dyspareunia and perineal pain 2
• Recurrent vaginal infections 2

The most common etiology is diverticulitis (79-89% of cases), followed by Crohn's disease, colorectal malignancy, radiation therapy, and iatrogenic injury. 3, 1

On physical examination, the fistula opening is typically visualized at the left vaginal apex in 90% of cases during speculum examination. 1

Diagnostic Work-Up

Imaging Modalities

MRI pelvis with IV gadolinium contrast is the preferred imaging modality, providing superior contrast resolution for evaluating fistulous tracts and detecting active inflammation. 2

CT pelvis with IV contrast is an acceptable alternative with diagnostic sensitivity of 76.5% for fistula detection and 94.1% for defining etiology. 4, 5

Specific imaging recommendations:

• Water-soluble contrast should be placed in the bowel to opacify fistulous tracts during CT imaging 4, 5
• Fluoroscopic vaginography has high sensitivity (79%) and positive predictive value (100%) for identifying fistulous tracts 6, 2
• Transvaginal ultrasound is recommended as an adjunct to optimally define vaginal fistulous openings 2
• Fluoroscopic contrast enema should be avoided as it cannot assess associated abscesses or the tract itself 2

Essential Imaging Documentation

Radiologic reports must specify: the exact location of the internal opening (colon vs. rectum), the course and length of the fistulous tract, the laterality of the vaginal opening, and classification as simple versus complex. 2

Document any associated abscesses with anatomical location and maximal diameter, signs of proctitis, and sphincter integrity. 2

Definitive Treatment

Surgical Management

Sigmoid resection with primary anastomosis is the definitive treatment of choice for colovaginal fistulas, achieving complete symptom resolution in 84% of patients. 1

A laparoscopic approach should be initiated when feasible, though conversion rates to open surgery can be as high as 42%. 3

Surgical principles:

• Multidisciplinary management involving colorectal surgery and gynecology is recommended 1
• Surgery should only be performed when there is endoscopic healing of the rectosigmoid mucosa 4
• At mean follow-up of 18 months, recurrence rates after sigmoid resection are essentially zero 3

Medical Management for Crohn's-Related Fistulas

For colovaginal fistulas secondary to Crohn's disease, infliximab is the initial medical treatment of choice, with azathioprine, 6-mercaptopurine, or methotrexate coadministered routinely for maintenance therapy. 4

Medical therapy outcomes in Crohn's disease:

• Complete fistula closure occurs in 38.3% of rectovaginal fistulas with medical therapy 4
• Antibiotics provide no lasting benefit 4
• Thiopurines result in 13% complete and 24% partial response 4
• Anti-TNF therapy achieves 17% complete and 30% partial response 4

Standard medical therapy must first control active luminal inflammatory disease in the rectosigmoid colon before considering surgical repair. 4

Treatment Algorithm

For non-Crohn's colovaginal fistulas (primarily diverticular): proceed directly to sigmoid resection with primary anastomosis. 3, 1

For Crohn's-related colovaginal fistulas: initiate infliximab with immunomodulator maintenance therapy; reserve surgery for medical failures or those with bowel obstruction or abscess formation. 4

Patients should be discussed in multidisciplinary meetings with treatment individualized based on etiology, symptoms, and surgical candidacy. 4

Important Caveats

Some women may choose to accept residual fistula drainage over proctectomy with ostomy to optimize overall quality of life, particularly when advancement flap procedures fail. 4

Advancement flap surgery should be reserved for patients with disabling symptoms due to risk of worsening symptoms in those in whom the operation fails. 4

As a last resort, fecal diversion or proctectomy may be undertaken for refractory cases. 4