What is the effectiveness of barium enema (barium enema) in diagnosing rectovaginal fistulas?

Effectiveness of Barium Enema in Diagnosing Rectovaginal Fistulas

Barium enema has very poor effectiveness for diagnosing rectovaginal fistulas, with sensitivity as low as 7.7-34%, and should not be used as the primary diagnostic method when this condition is suspected. 1, 2

Diagnostic Performance of Barium Enema vs. Alternative Methods

Barium enema performs poorly in detecting rectovaginal fistulas:

• Sensitivity of only 7.7% for all fistulas and 9% for those involving the colon only 1
• In sigmoid vaginal fistulae, detection rate of only 34% 1
• For urinary tract fistulas, contrast enema detected only 50% of colovesicular fistulas 1

Superior Alternative Diagnostic Methods:

1. Fluoroscopic Vaginography:

   • Sensitivity of 79% and positive predictive value of 100% 1, 2
   • Technique involves placing a large-gauge Foley catheter in the vaginal lumen with water-soluble contrast
   • Water-soluble contrast is strongly preferred over barium to avoid peritoneal complications 1

2. CT with IV Contrast:

   • Diagnostic sensitivity of 76.5% for fistula detection
   • 94.1% sensitivity for defining the etiology of the fistula 2
   • Water-soluble contrast should be placed in the bowel or bladder to opacify fistulous tracts 1

3. CT Vaginography:

   • Combines benefits of CT imaging with vaginal opacification
   • Performed with unenhanced scan followed by vaginal filling with diluted water-soluble contrast 1

4. MRI Pelvis with IV Contrast:

   • Particularly useful for visualizing collapsed tracts that don't contain fluid
   • Superior for soft tissue delineation 1

5. Transrectal Ultrasound:

   • High positive predictive value (100% for anorectal opening, 93% for vaginal opening) 1
   • More recent studies show improved detection rates compared to earlier reports 1

Important Clinical Considerations

Pitfalls to Avoid:

• Using barium instead of water-soluble contrast risks peritoneal contamination if perforation exists 1, 2
• Barium can cause streak artifacts on subsequent CT scans 1
• Catheter tip or balloon placement may inadvertently obscure distal fistulas 1
• Waiting at least 4 weeks after acute perianal surgery before imaging 2

Diagnostic Algorithm:

1. Begin with fluoroscopic vaginography as the initial investigation of choice for suspected rectovaginal fistulas 2, 3
2. If vaginography is inconclusive or additional anatomical detail is needed, proceed to CT with IV contrast or CT vaginography
3. For complex cases or when soft tissue detail is critical, MRI with IV contrast is recommended
4. Use transrectal ultrasound as a complementary method, particularly for identifying fistula openings

Patient Presentation:

Patients typically present with passage of stool, gas, or odorous discharge from the vagina, which may be confused with incontinence. Other symptoms include dyspareunia, perineal pain, and recurrent vaginal infections 1. These symptoms significantly impact quality of life and require prompt and accurate diagnosis.

Barium enema should be considered only when other, more sensitive imaging methods are unavailable, and even then, water-soluble contrast is preferred over barium to minimize complications 1, 2.