What is the treatment for an enterovesical fistula?

Management of Enterovesical Fistulas

The initial treatment for enterovesical fistulas should include antibiotics (ciprofloxacin 500 mg twice daily for 7-14 days), followed by anti-TNF therapy (infliximab) in combination with immunomodulators (azathioprine or 6-mercaptopurine), reserving surgery for refractory cases or those with associated complications. 1

Diagnostic Approach

• Pneumaturia (air in urine) is present in 88% of cases and is a strong clinical indicator of enterovesical fistula 2
• CT scan is the most sensitive diagnostic modality for detecting enterovesical fistulas 3
• Cystoscopy is useful for identifying the fistulous tract and evaluating the ureters 2
• Additional studies to consider:
  • Barium or gastrografin studies to identify concomitant enteroenteral fistulas
  • Colonoscopy to evaluate underlying bowel disease

Medical Management Algorithm

Step 1: Antibiotic Therapy

• Ciprofloxacin 500 mg orally twice daily for 7-14 days 1
• Alternative or combination: Metronidazole 400 mg three times daily 1

Step 2: Immunomodulator Therapy

• Azathioprine 1.5-2.5 mg/kg/day 1
  • Complete response rate: 13%
  • Partial response rate: 24%
• Alternative: 6-Mercaptopurine 0.75-1.5 mg/kg/day 1
• Note: These agents have slow onset of action and are more useful for maintaining fistula closure than for initial reduction 1

Step 3: Anti-TNF Therapy

• Infliximab induction: 5 mg/kg at weeks 0,2, and 6 1
• Maintenance: 5 mg/kg every 8 weeks 1
  • Complete response rate: 17%
  • Partial response rate: 30%
• Should be administered in combination with immunomodulators to prevent immunogenicity 1

Surgical Management

Surgery is indicated for:

• Refractory cases not responding to medical therapy
• Sigmoidovesical fistulas
• Associated complications:
  • Intestinal obstruction
  • Abscess formation
  • Ureteral obstruction 1

Surgical Approach

• Resection of the affected bowel segment
• Closure of bladder defect in two layers using absorbable suture
• Consider omental patch to reinforce repair 2

Treatment Outcomes

• Medical treatment can achieve complete closure of the fistula in 65.9% of cases 1
• Approximately 35.1% of patients can avoid surgery long-term with adequate medical treatment 1
• However, 64.9% of patients will eventually require surgical intervention due to intractable disease 1

Important Considerations

• Diverting colostomy alone is ineffective - all patients treated with diverting colostomy have persistent fistulas and urinary sepsis 4
• One-stage resection of involved bowel is the procedure of choice in the absence of abscess or bowel obstruction 4
• When resection is not feasible, medical management with antibiotics is preferable to colostomy 4
• Patients with enterovesical fistulas should be evaluated for Crohn's disease, diverticulitis, or malignancy as these are the most common causes 4, 3

Pitfalls to Avoid

• Relying solely on radiologic studies to identify the fistula - up to 20% of fistulas may not be identified on imaging studies despite being confirmed at operation 4
• Failing to evaluate for underlying malignancy - colorectal cancer is a common cause of enterovesical fistulas and may be missed preoperatively 4
• Performing diverting colostomy alone, which does not resolve the fistula and leads to persistent urinary sepsis 4
• Delaying treatment, which can lead to complications such as recurrent urinary tract infections, sepsis, and deterioration of quality of life 2