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Source created 2026-08-25 · updated 2026-08-25
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ASCRS Ch44 - IBD Diagnosis and Evaluation

Chapter 44, "IBD Diagnosis and Evaluation," ASCRS Textbook of Colon and Rectal Surgery, 4th edition. Authors: Mantaj S. Brar and Helen MacRae. Book pp. 751–764 (title page through References).

Textbook reference chapter (not primary literature), Part IV/benign-and-miscellaneous material. Mainly a reconciliation chapter: substantially deepens the existing Inflammatory Bowel Disease, Crohn Disease, and Ulcerative Colitis pages across classification, diagnostic workup (labs, imaging, endoscopy, histology), and — genuinely new to the wiki — a full suite of endoscopic/activity scoring systems and a risk-stratified colorectal cancer surveillance framework.

Structure

  • IBD Phenotypes / Crohn's vs. UC: Table 44.1 distinguishing features (distribution, ileal/ perianal involvement, bowel-wall depth, creeping fat, skip lesions, fistulas, deep ulceration/fissures, strictures); pathologists' limited ability to reliably distinguish UC/CD on biopsy.
  • IBD-Unclassified (IBD-U) and Indeterminate Colitis: ~10% of adult-onset, up to 30% of pediatric-onset IBD; IBD-U (pre-colectomy label) vs. indeterminate colitis (post-colectomy pathologic diagnosis); ~25% of IBD-U reclassified within 5 years, 2/3 to UC.
  • PSC-IBD: pancolitis with rectal sparing, right>left inflammation, backwash ileitis, milder symptoms despite endoscopic activity, higher medical-treatment response rate; colectomy timing linked to liver-transplant prognosis; poorer ileoanal pouch graft survival after transplant for PSC.
  • Extraintestinal Manifestations: Table 44.2 EIMs stratified by organ system and by association with intestinal activity (associated / unclear / not associated); common non-EIM manifestations of IBD activity/treatment (anemia, osteopenia, cholelithiasis, nephrolithiasis, tubulointerstitial nephritis, VTE).
  • Diagnostic Evaluation: labs/stool tests (CBC, electrolytes, creatinine, LFTs, iron studies; CRP correlates better with CD than UC, can be normal in up to 30% of active CD; ESR limited utility; stool culture/O&P/C. diff toxin; anal STI swabs if relevant history; pANCA+ASCA combined 70%/93% sensitivity/specificity for UC-vs-CD differentiation once IBD diagnosis established; fecal calprotectin pooled 93–95%/90–96% sensitivity/specificity, <50 mcg/g supporting avoidance of invasive testing).
  • Diagnostic Imaging: CT/CT enterography (CTE); MR enterography (MRE, sensitivity/specificity by small-bowel vs. colonic disease, novel diffusion-weighted/delayed-enhancement techniques for fibrosis quantification); ultrasound (transabdominal, elastography, transperineal/transanal for perianal disease); MR pelvis for perianal fistula characterization.
  • Endoscopy: colonoscopy with terminal ileal intubation as gold standard; biopsy protocol (≥2 terminal ileum + ascending/transverse/descending/sigmoid + rectum, separate vials); flexible sigmoidoscopy sufficient in severe acute colitis; upper GI endoscopy indications; capsule endoscopy/balloon enteroscopy for isolated small bowel Crohn's.
  • Histology: Table 44.3 (endoscopic lesion terminology) and Table 44.4 (UC vs. CD histologic features incl. Paneth cell metaplasia, pyloric gland metaplasia, neuronal hyperplasia, muscular hypertrophy); pathologist inter-observer accuracy for UC-vs-CD only 64–74% even among experts.
  • Genetic Studies: >240 GWAS loci; limited clinical utility of genetic testing despite twin-study heritability evidence; guideline-recommended testing scenarios (monogenic disorders, very-early- onset <5yo, aggressive/refractory young-onset IBD, TPMT/NUDT15 before thiopurine initiation).
  • Classification and Grading: Montreal and Paris classification for Crohn's (Table 44.5 — age, location incl. L4a/L4b upper-GI subdivision, behavior, perianal-p modifier, pediatric growth delay) and for UC (Table 44.6 — extent E1–E3, severity S0–S3, Pediatric UC Activity Index).
  • Endoscopic Scores: Mayo endoscopic subscore (Table 44.7) and Modified Mayo Endoscopic Score (MMES) for UC; SES-CD (Table 44.8) vs. CDEIS for Crohn's; Rutgeerts score (Table 44.9, i0–i4) for grading neoterminal ileal recurrence after ileocolic resection.
  • Activity Scores: Mayo score (0–12, UC, rarely used clinically); Crohn's Disease Activity Index (CDAI, <150 = remission, trial use only); Harvey-Bradshaw Index (Table 44.10, practical clinical alternative to CDAI); >20 newer patient-reported outcome measures (PROMs).
  • Surveillance Endoscopy in IBD: CRC risk factors (early-onset disease, longer duration, active inflammation, colonic strictures, PSC, family history); risk-stratified surveillance intervals (annual for high-risk, 1–3 years intermediate-risk, 3–5 years low-risk; start at 8 years post- symptom-onset or at PSC diagnosis); chromoendoscopy vs. standard-definition colonoscopy (2 recent RCTs show no added dysplasia-detection benefit); 4-random-biopsies-per-10cm protocol; SCENIC guideline terminology (Table 44.11) replacing "DALM" (dysplasia-associated lesion or mass).

Open items / gaps

  • Every named study/RCT in this chapter (the 2 chromoendoscopy-vs-standard-definition RCTs, the MRE multicenter cohort study, the fecal calprotectin meta-analyses, the pANCA+ASCA combination study) is cited at the textbook/secondary level only — see the individual condition pages' own Open items for what would be highest-value to independently ingest.
  • Chapter 45 ("Medical Management of Ulcerative Colitis," Lightner AL, Strong SA) begins next — its opening framing (homeopathic agents, 5-ASA compounds, glucocorticoids, early immunomodulator content through calcineurin inhibitors) was visible in this read but not yet ingested; likely a significant reconciliation target against Ulcerative Colitis's existing ACG/AGA/BSG-guideline- sourced medical management section.