Standardized Examination Under Anesthesia for Rectovaginal Fistulae: The St Mark’s Protocol
Overview
Rectovaginal fistulae (RVFs) are challenging to diagnose and manage due to variable presentations and limitations of imaging. The St Mark’s protocol offers a standardized five-stage examination under anesthesia (EUA) to improve diagnostic accuracy and guide treatment decisions.
Background
Rectovaginal fistulae cause significant physical and psychological distress, often resulting from obstetric trauma, Crohn’s disease, or pelvic surgery. Diagnosis can be difficult, especially for subtle or low-lying fistulae, as imaging modalities like MRI and ultrasound have limitations. Examination under anesthesia remains the gold standard for definitive diagnosis and surgical planning. The St Mark’s protocol provides a systematic approach to EUA, enhancing detection and assessment of RVFs.
Data Highlights
The protocol consists of five stages: 1) Direct visual inspection using vaginal and rectal retractors to identify fistulous openings and assess sphincter integrity; 2) Intraoperative endoanal ultrasonography (EAUS) to delineate sphincter anatomy and fistula tract; 3) Use of fistula probes to confirm patency of small tracts; 4) Insufflation and bubble test to detect air passage through fistulae; 5) Methylene blue dye test to confirm persistent fistulous communication. This structured approach improves diagnostic confidence and operative planning.
Key Findings
RVFs have diverse etiologies and presentations, often requiring detailed assessment beyond imaging.
The five-stage St Mark’s EUA protocol standardizes evaluation, combining inspection, ultrasonography, probing, insufflation, and dye testing.
Intraoperative endoanal ultrasonography enhances anatomical detail and correlates with preoperative MRI findings.
Insufflation and bubble test effectively detect high fistulae not visible on inspection.
Methylene blue dye test confirms persistent fistulae by demonstrating dye passage from rectum to vagina.
The protocol facilitates documentation and informed intraoperative decision making, including timing of definitive repair.
Clinical Implications
The St Mark’s EUA protocol provides clinicians with a reproducible and comprehensive framework to diagnose and assess rectovaginal fistulae, especially in cases with ambiguous imaging or persistent symptoms. Incorporating intraoperative ultrasonography where available can improve anatomical understanding and surgical planning. This approach supports better patient counseling and tailored management strategies.
Conclusion
The St Mark’s five-stage EUA protocol offers a structured, reliable method for evaluating rectovaginal fistulae, enhancing diagnostic accuracy and guiding operative decisions. Its adoption may improve outcomes in this complex patient population.
References
St Mark’s Hospital Colorectal Unit -- Standardized Examination Under Anesthesia for Rectovaginal Fistulae: The St Mark’s Protocol
