Examination of Post-Surgical Rectovaginal Fistula

Clinical Presentation and Diagnosis

Patients with rectovaginal fistulas typically present with passage of stool, gas, or odorous mucopurulent discharge from the vagina, which may be confused with incontinence, according to the American College of Radiology 1
The American College of Radiology recommends determining if the fistula is high (rectovaginal) or low (anovaginal) based on symptoms and physical examination findings 1
Other common symptoms include dyspareunia, perineal pain, and recurrent vaginal infections, as reported by the American College of Radiology 1

The American College of Radiology suggests that MRI pelvis without and with IV contrast provides superior contrast resolution for evaluating fistulous tracts, with IV gadolinium contrast being essential for active inflammation in fistulous tracts and abscesses 2
The American College of Radiology recommends CT pelvis with IV contrast as an alternative to MRI, with comparable diagnostic utility and the use of IV contrast to help visualize and characterize fluid collections, abscesses, and fistulous tracts 3
Fluoroscopic vaginography has a high sensitivity (79%) and positive predictive value (100%) for fistulous tract identification, according to the American College of Radiology 4
Transrectal ultrasound can be useful in certain clinical scenarios, with improved detection rates in recent studies and a positive predictive value of 100% for identifying the anorectal opening and 93% for identifying the vaginal opening, as reported by the American College of Radiology 4

The American College of Radiology defines high fistulas (rectovaginal) as communications to the rectum proximal to the anal sphincter, often involving the posterior vaginal fornix, and low fistulas (anovaginal) as communications from the anal sphincter complex to the lower half of the vagina 1
Complex fistulas are those with extensions, multiple external openings, complicated by abscess, urogenital involvement, or anorectal stricture, according to the Journal of Crohn's and Colitis 5
The Journal of Crohn's and Colitis recommends documenting the position of internal opening, track characteristics, and vaginal or vulvar opening location, as well as reporting the size of any associated abscess and noting any signs of proctitis 5

The presence of polymicrobial enteric flora with anaerobes (Bacteroides, fusobacteria, anaerobic cocci) is more specific for fistulous communication with bowel, as stated by the American Heart Association 6, 7
Polymicrobial bacteremia with mixed enteric organisms including E. coli, enterococci, and anaerobes is highly suggestive of enteric fistula, according to the American Heart Association 6
A single vaginal swab showing only E. coli and GBS lacks the polymicrobial anaerobic pattern typical of fecal contamination, as noted by the American Heart Association 7

Early recognition of fistulas is crucial, as untreated fistulas can lead to severe complications including sepsis, as emphasized by the American Heart Association 6

Transvaginal ultrasound is recommended as an adjunct imaging technique to provide optimal definition of vulvar or vaginal fistulous openings in patients being evaluated for rectovaginal fistula. 8
Fluoroscopic contrast enema should be avoided because it does not allow assessment of associated abscesses or the fistulous tract itself. 9

Report the exact location of the internal fistulous opening (anus vs. rectum) in all imaging studies. 8
Describe the course of the fistulous tract, including direction and length, to facilitate surgical planning. 8
Specify the laterality (left or right) of the vaginal or vulvar external opening. 8
Classify the fistula as simple or complex (complex defined by multiple external openings, extensions, abscess involvement, urogenital involvement, or anorectal stricture) because management differs between these categories. 8

Document any abscesses, noting their anatomical location, maximal diameter in two perpendicular planes, and whether a horseshoe configuration is present, as these influence therapeutic decisions. 8
Record signs of proctitis on imaging, since active inflammation may affect timing of repair. 8
Assess and note sphincter integrity, which is essential when surgical repair is contemplated. 8

After an acute perianal surgical intervention, obtain interval imaging no earlier than four weeks to allow postoperative changes to settle and to accurately evaluate residual or recurrent fistulous disease. 8
When patients present with concurrent suspected perianal fistula and small‑bowel disease, combine intestinal and pelvic MRI (or intestinal ultrasound with endo‑anal/perineal ultrasound) in a single session to streamline diagnosis and reduce patient visits. 8

Do not rely on fluoroscopic contrast enema for fistula evaluation, as it cannot visualize abscesses or delineate the tract. 9