IBD IBD Diagnosis and Imaging 1 — Questions and Answers
Question 1: Which endoscopic finding is considered the gold standard for diagnosing Crohn's disease of the terminal ileum?
- Pseudopolyps
- Cobblestone mucosa with linear ulcers (Correct answer)
- Loss of haustra
- Continuous erythema from rectum
Correct answer: Cobblestone mucosa with linear ulcers
Cobblestone mucosa with linear ulcers separated by areas of relatively normal mucosa (skip lesions) is the classic endoscopic appearance of Crohn's disease.
Question 2: What is the preferred imaging modality for evaluating small bowel involvement in Crohn's disease?
- Plain abdominal X-ray
- CT enterography (CTE) or MR enterography (MRE) (Correct answer)
- Barium enema
- Abdominal ultrasound alone
Correct answer: CT enterography (CTE) or MR enterography (MRE)
CT enterography and MR enterography provide superior luminal and mural detail for assessing small bowel Crohn's disease extent, complications, and activity.
Question 3: Which fecal biomarker is most useful for monitoring intestinal inflammation and mucosal healing in IBD?
- Fecal occult blood (FOBT)
- Fecal calprotectin (Correct answer)
- Fecal lactoferrin
- C-reactive protein (CRP)
Correct answer: Fecal calprotectin
Fecal calprotectin is a sensitive, non-invasive marker of intestinal inflammation that correlates well with endoscopic disease activity and mucosal healing.
Question 4: On colonoscopy, the finding of 'backwash ileitis' can occur in which IBD condition?
- Crohn's disease limited to ileum
- Extensive ulcerative colitis (pancolitis) (Correct answer)
- Microscopic colitis
- Diversion colitis
Correct answer: Extensive ulcerative colitis (pancolitis)
Backwash ileitis occurs in severe pancolitis UC when reflux of colonic contents causes mild ileal inflammation, distinguishable from Crohn's ileitis by its limited extent and diffuse pattern.
Question 5: Which serological marker combination pattern is most consistent with ulcerative colitis?
- pANCA positive, ASCA negative (Correct answer)
- ASCA positive, pANCA negative
- Both pANCA and ASCA positive
- Both pANCA and ASCA negative
Correct answer: pANCA positive, ASCA negative
pANCA positivity with ASCA negativity has the highest specificity for ulcerative colitis in serological IBD differentiation panels.
Question 6: Which radiological sign on plain abdominal X-ray suggests toxic megacolon as a complication of IBD?
- Lead pipe sign
- Thumbprinting
- Transverse colon diameter >6 cm with mucosal edema (Correct answer)
- String sign of Kantor
Correct answer: Transverse colon diameter >6 cm with mucosal edema
Toxic megacolon is diagnosed when the transverse colon dilates to >6 cm (or cecum >9 cm) with associated systemic toxicity and mucosal edema on X-ray.
IBD IBD Diagnosis and Imaging 1
Which endoscopic finding is considered the gold standard for diagnosing Crohn's disease of the terminal ileum?