What is the most appropriate next step for a 34-year-old female with a 1-year history of perianal discharge and perianal fistulas at 7 and 3 o'clock positions, without changes in bowel habits?

Most Appropriate Next Step for Perianal Fistulas

Both pelvic MRI and colonoscopy should be performed, but if forced to choose a single next step, colonoscopy (proctosigmoidoscopy) takes priority because the presence of rectosigmoid inflammation has critical prognostic and therapeutic implications that will fundamentally alter management strategy. 1

Why Colonoscopy Should Be Done First

The ECCO-ESCP consensus explicitly states that proctosigmoidoscopy should be used routinely in the initial evaluation because concomitant rectosigmoid inflammation has both prognostic and therapeutic relevance. 1 This is critical because:

• Perianal fistulas may be the presenting manifestation of Crohn's disease, which occurs in 14-23% of CD patients, and perianal disease can precede intestinal symptoms. 1
• The presence of rectal inflammation dramatically affects treatment decisions—you cannot proceed with definitive surgical repair if active rectal disease is present. 1
• In patients with colonic disease and rectal involvement, the prevalence of fistulizing anal disease reaches 92%. 1
• This 34-year-old female fits the demographic profile, as the highest incidence of perianal CD occurs in young adults aged 16-30 years. 1

Why MRI Is Also Essential (But Can Follow)

While contrast-enhanced pelvic MRI is considered the initial imaging procedure for assessment of perianal fistulizing disease 1, 2, it primarily provides anatomical information about fistula complexity, secondary tracts, and abscesses. The MRI will help classify whether these are simple or complex fistulas and guide surgical planning. 1, 2

However, the MRI findings alone won't tell you if this is cryptoglandular disease versus Crohn's disease—that determination requires endoscopic evaluation of the rectosigmoid colon. 1

Clinical Algorithm

Step 1: Perform colonoscopy/proctosigmoidoscopy to:

• Assess for rectosigmoid inflammation suggesting Crohn's disease 1
• Evaluate for ulceration, strictures, or other luminal disease 1, 2
• Determine if medical therapy for luminal disease is needed before surgical intervention 1, 3

Step 2: Obtain pelvic MRI to:

• Define fistula anatomy (simple vs. complex) 1, 2
• Identify secondary tracts or abscesses 1, 2
• Guide surgical planning 1

Step 3: Consider examination under anesthesia (EUA) by experienced surgeon for definitive classification and potential seton placement. 1, 2

Critical Pitfalls to Avoid

• Do not assume these are simple cryptoglandular fistulas in a young woman without first ruling out Crohn's disease, as this fundamentally changes management from primarily surgical to medical-surgical combined approach. 1, 3
• Do not proceed with definitive surgical repair (advancement flaps, fistulotomy) without first confirming absence of active rectal inflammation, as this leads to high failure rates. 1, 3
• Do not delay evaluation thinking this will resolve spontaneously—after 1 year of symptoms, these fistulas require active intervention. 2, 3

Nuance in the Evidence

The guidelines consistently emphasize that both imaging (MRI) and endoscopy are complementary and essential for complete evaluation. 1 The ECCO-ESGAR guidelines state that "endoscopic evaluation of the rectum is essential to determine the most appropriate management strategy." 1 This is because treatment diverges dramatically:

• If Crohn's disease is present: Medical therapy with antibiotics, immunomodulators, or anti-TNF agents combined with seton placement 1, 2, 3
• If cryptoglandular disease: Primarily surgical management with fistulotomy for simple fistulas 1, 2, 3

The presence of proctitis is associated with lower rates of fistula healing and requires concurrent treatment of luminal disease. 3