Is the presence of E. coli and GBS (Group B Streptococcus) in vaginal discharge a clue that there is stool in the vagina, suggesting a fistula, in a patient who had a total robotic hysterectomy and presents with tannish yellow discharge in the upper vagina?

E. coli and GBS in Vaginal Discharge After Hysterectomy: Fistula Evaluation

The presence of E. coli and GBS alone in vaginal discharge is NOT a definitive indicator of a rectovaginal fistula, as these organisms can colonize the vagina normally; however, E. coli in the upper vagina combined with tannish yellow discharge after pelvic surgery should raise strong suspicion for a fistula and warrants immediate imaging evaluation.

Understanding the Microbiology

Normal vs. Pathological Flora

• GBS (Group B Streptococcus) is a common vaginal colonizer, found in approximately 16-27% of healthy pregnant women and can persist in non-pregnant women 1
• E. coli can be present in vaginal cultures without fistula formation, as it represents approximately 3.5-10% of normal vaginal/cervical colonization 2
• The key distinction is that polymicrobial enteric flora with anaerobes (Bacteroides, fusobacteria, anaerobic cocci) is more specific for fistulous communication with bowel 3

What Would Be More Specific for Fistula

• Polymicrobial bacteremia with mixed enteric organisms including E. coli, enterococci, and anaerobes is highly suggestive of enteric fistula 3
• A single vaginal swab showing only E. coli and GBS lacks the polymicrobial anaerobic pattern typical of fecal contamination 3
• The pathognomonic clinical presentation of rectovaginal fistula includes passage of stool, gas, or odorous mucopurulent discharge from the vagina 1

Clinical Approach to Your Patient

High-Risk Context

• Iatrogenic injury during pelvic surgery (particularly hysterectomy) is the primary cause of genitourinary fistulas, with initially unrecognized injury presenting in a delayed manner 4
• Post-hysterectomy patients can develop rectovaginal, vesicovaginal, or ureterovaginal fistulas 1, 4
• Tannish yellow discharge in the upper vagina could represent urine (ureterovaginal or vesicovaginal fistula) rather than stool 4

Immediate Diagnostic Steps

• Order MRI pelvis without and with IV contrast as the first-line imaging study, which provides superior contrast resolution for evaluating fistulous tracts and is essential for detecting active inflammation 1
• CT pelvis with IV contrast is an acceptable alternative with comparable diagnostic utility for visualizing fluid collections, abscesses, and fistulous tracts 1
• Perform careful physical examination looking for: visible fistula opening in vaginal vault, passage of gas or stool from vagina, and location of discharge (high vs. low vagina) 1
• Consider fluoroscopic vaginography, which has 79% sensitivity and 100% positive predictive value for fistulous tract identification 1

Critical Pitfalls to Avoid

• Do not assume E. coli presence alone confirms fecal contamination - this organism colonizes the vagina in up to 10% of women without fistula 2
• Do not delay imaging while waiting for more symptoms - early recognition is crucial as untreated fistulas can lead to severe complications including sepsis 3
• Do not confuse rectovaginal fistula with ureterovaginal or vesicovaginal fistula - they have different presentations and management approaches 5, 1, 4
• Consider that recurrent urinary tract infections are a common manifestation of vesicovaginal fistulae, which could also explain E. coli presence 5

Additional Diagnostic Considerations

• Check for pneumaturia and fecaluria if you suspect rectovesical involvement (though this is less likely given the vaginal discharge location) 5
• Document whether discharge contains visible stool particles, has fecal odor, or if patient reports passage of gas from vagina - these are more specific than culture results alone 1
• If imaging confirms fistula, document the position of internal opening, track characteristics, size of any abscess, and signs of proctitis 1