What is the condition called when the colon grows into the bladder and what are the expected changes in urine appearance?

Colovesical Fistula: Diagnosis and Urine Characteristics

When the colon grows into the bladder, it is called a colovesical fistula, and the urine typically appears cloudy, may contain fecal material, and often has a foul odor due to bacterial contamination.

Clinical Presentation and Diagnosis

Characteristic Symptoms

• Pneumaturia (air in urine) - pathognomonic sign
• Fecaluria (fecal material in urine) - pathognomonic sign
• Recurrent urinary tract infections (73% of cases) - most common presenting symptom 1
• Dysuria and urinary frequency
• Abdominal pain
• Hematuria

Urine Characteristics

• Cloudy appearance due to bacterial contamination
• Fecal particles may be visible in severe cases
• Foul odor (often described as feculent)
• Positive urine cultures for intestinal bacteria (polymicrobial)
• Gas bubbles may be present in collected specimens

Diagnostic Evaluation

Imaging Studies

1. CT with contrast (highest diagnostic accuracy)

   • Can identify the fistulous tract
   • May show enhancing tract extending from colon to bladder wall
   • May show focal bladder wall thickening 2

2. Cystography (90% diagnostic rate) 3

   • May show contrast entering the sigmoid colon

3. Barium enema (75% diagnostic rate) 3

Direct Visualization

• Cystoscopy (69% diagnostic rate) 3
  • May reveal granulomatous lesion at the fistula site
  • Fecal material may be seen coming through the fistula

Etiology

The most common causes of colovesical fistula include:

1. Diverticulitis (most common benign cause)
2. Colorectal cancer (most common malignant cause)
3. Inflammatory bowel disease (particularly Crohn's disease)
4. Radiation therapy complications
5. Iatrogenic injury during pelvic surgery

Management Considerations

Medical Management

• Antibiotics for urinary tract infections
• Treatment of underlying cause (e.g., diverticulitis)

Surgical Management

• One-stage surgical approach is preferred for most patients 1

  • Resection of involved bowel segment
  • Closure of bladder defect
  • Primary anastomosis when possible

• Multi-stage approach reserved for:

  • Patients with pelvic abscess
  • Advanced malignancy
  • Previous radiation therapy 1

Surgical Approaches

• Open surgery (traditional approach)
• Laparoscopic repair (when performed by skilled surgeons)
• Robotic-assisted repair (may reduce conversion rates) 1

Clinical Pearls and Pitfalls

• Pearl: The combination of pneumaturia and fecaluria is virtually pathognomonic for colovesical fistula
• Pitfall: Treating recurrent UTIs with antibiotics without investigating for underlying fistula
• Pearl: CT cystography is not usually needed for initial diagnosis but may provide additional information for surgical planning 2
• Pitfall: Failing to consider colovesical fistula in elderly patients with unexplained recurrent UTIs, especially those with history of diverticulitis or colorectal cancer

Special Considerations

• Colovesical fistula may rarely be the presenting sign of metastatic cancer from distant sites, including lung cancer 4
• The rectum (52%) and sigmoid colon (39%) are the most common sites involved in enterovesical fistulas 3