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Source created 2026-08-25 · updated 2026-08-25
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ASCRS Ch47 - Anorectal Crohn's Disease

Chapter 47, "Anorectal Crohn's Disease," ASCRS Textbook of Colon and Rectal Surgery, 4th edition. Authors: Emily Steinhagen and Andrea Chao Bafford. Book pp. 799–812 (title page through References).

Textbook reference chapter (not primary literature), Part IV/benign-and-miscellaneous material. The wiki's Crohn Disease page had explicitly flagged this chapter as still-pending for its perianal-disease section (a note left when Anal Fistula (ASCRS Ch13) was ingested, since that page excludes Crohn's fistulas from its cryptoglandular treatment ladder). Substantially deepens Crohn Disease's perianal-disease coverage (pathogenesis, classification, diagnosis, medical and surgical management of fistulizing disease, non-fistulizing complications, diversion/proctectomy) and adds a much stronger stem-cell-therapy data point to Rectovaginal Fistula's existing Crohn's-RVF coverage.

Structure

  • Epidemiology and pathogenesis: perianal fistula incidence rises with disease duration/ severity/distal involvement — 12% with ileal disease, 15% ileocolonic, 41% colonic sparing the rectum, 92% colonic+rectal disease; perineal fistulas correlate with colonic (vs. isolated ileal) disease; recurrent fistula activity risk 48% at 1 year, 59% at 2 years. Two proposed pathogenesis mechanisms: (1) rectal inflammation → ulcers/shallow fistulas extended deeper by feces/pressure during defecation (thought to explain CD-related fistulas specifically), (2) infected anal glands penetrating the intersphincteric space (thought to explain idiopathic/cryptoglandular fistulas).
  • Abscess: up to 62% of perianal CD patients develop an anorectal abscess, most commonly ischiorectal (40% of CD-related perirectal abscesses); intersphincteric/supralevator abscesses often need CT/endorectal ultrasound/MRI for diagnosis given subtle clinical signs. Prompt surgical drainage required regardless of medical therapy plans.
  • Fistula classification: Parks anatomical classification (relationship to external sphincter); AGA empiric simple-vs-complex system layered on top for CD (simple = low, single opening, no pain/fluctuance/stricture/RVF; complex = high, multiple openings, or associated with abscess/stricture/RVF/active rectal disease at endoscopy).
  • Diagnosis: multimodal (physical exam, EUA, imaging). A triple-blinded study found EUA, MRI, and endorectal ultrasound (ERUS) each 91%/87%/91% accurate individually, with any two combined reaching 100% accuracy. A separate synthesis found MRI's likelihood ratio for confirming complex disease (22.7) far exceeds clinical exam (2.1) or ERUS (6.2) — MRI regarded as the gold-standard imaging modality for perianal CD by multiple societies including ECCO. EUA without preceding imaging is likely adequate for simple fistulas; preoperative MRI is recommended before EUA for complex fistulas.
  • Medical management: antibiotics (ciprofloxacin/metronidazole) as a bridge to immunosuppressant therapy, not sole therapy — two RCTs found ciprofloxacin improved response when combined with infliximab (73% vs. 39%) or adalimumab (71% vs. 47%); a systematic review/ meta-analysis of antibiotics for CD fistula found RR 0.8 for reduced drainage (NNT 5). Thiopurines best used combined with anti-TNF rather than as first-line (meta-analysis: fistula response 54% thiopurine vs. 21% placebo, OR 4.44); delayed onset (3+ months) means used for maintenance not induction of fistula closure. Calcineurin inhibitors (tacrolimus, cyclosporine) reserved for severe/intolerant/multimodality-refractory disease given toxicity (nephrotoxicity, need for close drug monitoring). Biologics (concrete RCT-level numbers, genuinely new depth): infliximab (RCT of 85 patients: ≥50% fistula closure maintained ≥4 weeks in 68%/56% at 5/10 mg/kg vs. 26% placebo; ACCENT II trial, 306 patients, week-54 complete closure 39% infliximab-maintenance vs. 19% placebo); adalimumab (CHARM trial: 30% vs. 13% fistula closure at 26 weeks); certolizumab (PRECiSE trials: 54% vs. 43% fistula closure, did not reach statistical significance); vedolizumab (GEMINI 2 subgroup: 28% vs. 11% fistula closure at 14 weeks, 33% vs. 11% at 52 weeks); ustekinumab (small retrospective series: 61%/31% symptom improvement/closure). Combining anti-TNF with thiopurines, ciprofloxacin, or EUA may further improve response.
  • Surgical management: fistulotomy (safe without proctitis; 73%/93% wound healing at 3/6 months in one series of 41 fistulotomies; CDAI >150 a relative contraindication); draining seton (loose, thin, silastic — placed with medical therapy for complex fistulas, may remain months to years, removal after active proctitis addressed medically, typically after anti-TNF induction complete — a systematic review of 10 studies/305 seton+anti-TNF patients found closure rates 13.6–100%, recurrence 0–83%); endorectal advancement flap (60–64% success, 57% recurrence, 9.4% incontinence in various series; concomitant small bowel disease and smoking predict worse outcomes; relative contraindications include proctitis, cavitating ulceration, anal stenosis; the "advancement rectal sleeve" is a described alternative for severe complex disease); LIFT (two small retrospective series: 67% healing at 12 months in 15 patients with no incontinence; 75%/33% healing at <1yr/

    1yr follow-up in another; better outcomes in small-bowel vs. colonic CD); fibrin glue/fistula plugs (highly variable 0–100% reported healing; one multicenter RCT found plug and seton-removal- alone had similar efficacy); mesenchymal stem cell therapy — a phase 3 RCT of 212 CD patients with complex fistulas found adipose-derived stem cell injection achieved higher fistula closure than placebo (56.3% vs. 38.6%, p=0.010) with shorter time to remission; a meta-analysis of 11 studies found improved healing with MSCs vs. placebo at 6–24 weeks (OR 3.06) and 24–52 weeks (OR 2.37) — genuinely new, considerably stronger primary-trial-level evidence than the wiki's existing 10-patient uncontrolled series citation on Rectovaginal Fistula.

  • Rectovaginal fistula: ~10% incidence in CD women, median onset age 34; colonic disease distribution most associated. Control of sepsis/optimized medical management prerequisite to repair. Advancement flap (42% initial healing rising to 83% after up to 3 attempts in one series); vaginal flap alternative when anal stenosis present; Martius (gracilis/bulbocavernosus) flap (33–80% healing across small series, none >11 patients); biologic mesh (50–78% healing, very limited data); anal fistula plug (50% healing); a separate RCT of stem cell injection found 51% vs. 35% remission at 24 weeks. Up to 60% of CD-RVF patients require temporary fecal diversion, up to half require permanent stoma. Immunomodulators improve healing; smoking and steroid use decrease success.
  • Non-fistulizing complications: anal fissures/ulcers (idiopathic-appearing fissures treated like non-CD fissures; atypical CD fissures are often multiple, off-midline, with granulating base/overhanging edges — sphincter-tone-lowering therapies like botulinum toxin/LIS should generally be avoided given hypotonic sphincters and continence risk already present in many CD patients, though LIS may suit a select subgroup with a single midline fissure, hypertonic sphincter, and disease-free rectum; systemic anti-TNF is the treatment gold standard with 43% complete healing in one large retrospective study); skin tags (Type 1 — edematous/tender, sequelae of fissures/ulcers/hemorrhoids from lymphedema; Type 2 — painless "elephant ear" tags, ~19% 10-year cumulative incidence; generally managed conservatively, excision reserved for remission-phase patients with hygiene/QoL impact given uncertain complication risk); hemorrhoids (uncommon in CD — only 20 of 50,000 hemorrhoid patients in one cohort had CD; poor historical surgical outcomes likely reflect association with severe distal disease rather than causation; a modern series of 36 CD patients undergoing excisional hemorrhoidectomy found only 4 complications, suggesting carefully selected patients — luminal remission, no steroids, CDAI <150 — may do well); anal stricture (17% of perianal CD, rarely without other perianal disease; dilation — manual, balloon, or Hegar — for symptomatic strictures, repeated as needed without being considered treatment failure; ~50% eventually require proctectomy); anal cancer (adenocarcinoma and squamous cell carcinoma risk increased with long-standing perianal CD, arising in the anal canal or chronic fistula tracts; a long-standing previously-asymptomatic fistula that acutely becomes symptomatic, or a newly inflamed chronic fissure, should raise suspicion for malignant degeneration; treatment mirrors sporadic anal cancer).
  • Diversion and proctectomy: severe perianal CD requires temporary or permanent fecal diversion in 10–20% of cases; risk increased with active rectal disease and anal stricture. Staged proctectomy often most appropriate when active inflammation present (rectal transection at levator level with permanent stoma first, limited perineal anoproctectomy once recovered, intersphincteric dissection sparing external sphincter to minimize perineal wound size/risk). Primary perineal- wound closure associated with poor healing in up to 1/3 of patients; nonhealing wounds may need skin grafting or myocutaneous flap reconstruction.

Open items / gaps

  • Every named trial/study in this chapter (ACCENT II, CHARM, PRECiSE, GEMINI 2, the 212-patient phase-3 stem-cell RCT, the triple-blinded EUA/MRI/ERUS accuracy study) is cited at the textbook/ secondary level only — see Crohn Disease's and Rectovaginal Fistula's own Open items for what would be highest-value to independently ingest.
  • Chapter 48 ("Crohn's Disease: Surgical Management," Cannon LM, Fichera A) begins next — its opening framing (declining surgery rates over decades — 73%/61%/71% at 1/5/10 years in a 1955–1989 cohort vs. 29%/24.6%/28.5% in a 2003–2004 cohort; Table 48.1 operative indications; bowel obstruction fibrosis-vs-inflammation imaging distinction; balloon dilation pooled outcomes from 1463 patients/3000+ procedures; penetrating disease/abscess management) was visible in this read but not yet ingested; likely a significant reconciliation target against Crohn Disease's existing surgical-treatment sections (colonic- and small-bowel-focused, from the Sabiston chapters) — this ASCRS chapter appears more current/guideline-adjacent than that older textbook source.