What are the characteristics and treatment options for perianal Crohn's disease?

Characteristics of Perianal Crohn's Disease

Perianal Crohn's disease typically occurs early in the disease course, with fistulas usually being single rather than multiple, and granulomas frequently found on biopsy. Fecal diversion is not curative, and lesions are typically located anteriorly rather than posteriorly. 1

Epidemiology and Natural History

• Perianal Crohn's disease affects approximately 14-23% of Crohn's disease patients, with cumulative incidence increasing with time from diagnosis 1
• Perianal disease may precede intestinal symptoms, appear at diagnosis, or develop later in the disease course 1
• The risk of developing perianal fistulas is highest in patients with colonic disease with rectal involvement, reaching up to 92% prevalence in this population 1
• Young adults (16-30 years) show the highest incidence of perianal disease, with a second peak observed in elderly patients (76-90 years) 1
• Men are more likely to develop perianal disease than women (15.8% vs 11.6%) 1

Clinical Characteristics

• Perianal fistulas are typically single rather than multiple, contrary to option (b) in the question 1, 2
• Lesions are typically located anteriorly rather than posteriorly, making option (d) incorrect 1, 3
• Granulomas are frequently found on biopsy of perianal lesions, contradicting option (e) 1, 3
• Perianal disease often presents early in the disease course rather than late, making option (a) incorrect 1, 4

Diagnostic Approach

• Contrast-enhanced pelvic MRI is the recommended initial procedure for assessment of perianal fistulizing CD 1
• Endoscopic anorectal ultrasound (EUS) is a good alternative if rectal stenosis is excluded 1
• Examination under anesthesia (EUA) is considered the gold standard when performed by an experienced surgeon 1
• Proctosigmoidoscopy should be routinely used in initial evaluation to assess for concomitant rectosigmoid inflammation 1

Treatment Considerations

• Fecal diversion (temporary diverting ileostomy or colostomy) is not curative for perianal Crohn's disease, making option (c) incorrect 1
• Studies have shown that most patients who undergo temporary diversion never have intestinal continuity restored 1
• The primary treatment approach involves drainage of sepsis as first-line therapy before initiating immunosuppressive treatment 1
• Seton placement in combination with antibiotics is the preferred strategy for symptomatic simple perianal fistulas 1
• Anti-TNF therapy is considered the gold standard medical treatment for complex perianal fistulas 1

Surgical Management

• Simple fistulotomy may be considered for uncomplicated low anal fistulas 1
• For complex fistulas, seton placement after surgical treatment of sepsis is recommended 1
• Definitive surgical repair should only be considered in the absence of luminal inflammation 1
• Historically, proctectomy rates for patients with perianal Crohn's disease managed conservatively range from 10% to 18% 1

Complications and Special Considerations

• Patients with perianal Crohn's disease have an increased risk of undergoing major abdominal surgery compared to those without perianal involvement 4
• There is an increased risk of anal and rectal cancer in patients with perianal Crohn's disease compared to non-IBD controls 4
• Pregnant patients with active perianal Crohn's disease at the time of delivery should undergo cesarean section 1

Perianal Crohn's disease represents a complex manifestation that requires a multidisciplinary approach involving both medical and surgical interventions, with treatment strategies tailored to the specific type of perianal lesion and presence of concomitant luminal disease.