Crohn disease vs Ulcerative colitis
How to tell Crohn disease and Ulcerative colitis apart when a board question makes them look alike.
Crohn: transmural, skip lesions, granulomas, mouth to anus. UC: continuous mucosal disease from the rectum, no granulomas.
Side by side
Skip lesions, transmural inflammation, fistulas, strictures, RLQ pain, or perianal disease.
Continuous mucosal inflammation beginning in the rectum with bloody diarrhea.
Patchy full-thickness intestinal inflammation can involve mouth to anus.
Superficial colonic inflammation extends proximally from the rectum.
Noncaseating granulomas, creeping fat, and cobblestoning favor Crohn disease.
Crypt abscesses and continuous colitis favor ulcerative colitis.
The trap
Both cause bloody diarrhea, weight loss, and extraintestinal disease (arthritis, uveitis, erythema nodosum, pyoderma gangrenosum, primary sclerosing cholangitis), so symptoms overlap. The discriminator is depth and distribution on endoscopy and biopsy: transmural skip lesions with possible perianal disease, fistulas, or abscesses is Crohn; continuous mucosal disease starting at the rectum is UC. Colon cancer surveillance is needed in both, but the risk is higher in long-standing pancolitis UC.
Watch it explained
The repair move
Do not start with diarrhea. Start with depth, distribution, and rectal involvement.
Try a free question
CoreA young adult has chronic diarrhea, weight loss, RLQ pain, perianal fistulas, and patchy ileal inflammation with skip lesions. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Crohn disease. Transmural inflammation with skip lesions and fistulas points to Crohn disease.
Why the other choices are tempting
- B. Ulcerative colitis is continuous mucosal disease beginning in the rectum.
- C. Ischemic colitis usually affects watershed areas in older vascular-risk patients.
- D. Celiac disease causes malabsorption from gluten-sensitive enteropathy.
- E. Diverticulitis causes focal colonic inflammation with fever and LLQ pain.
Flashcards
Tap a card to flip it.
What distribution clue favors Crohn disease?
Patchy skip lesions, especially with terminal ileal involvement, favor Crohn disease.
What distribution clue favors ulcerative colitis?
Continuous colonic inflammation beginning at the rectum favors ulcerative colitis.
Quick answers
What is the fastest way to tell Crohn disease from Ulcerative colitis?
Crohn: transmural, skip lesions, granulomas, mouth to anus. UC: continuous mucosal disease from the rectum, no granulomas.
What is the key clue for Crohn disease?
Skip lesions, transmural inflammation, fistulas, strictures, RLQ pain, or perianal disease.
What is the key clue for Ulcerative colitis?
Continuous mucosal inflammation beginning in the rectum with bloody diarrhea.
What is the common trap with Crohn disease vs Ulcerative colitis?
Both cause bloody diarrhea, weight loss, and extraintestinal disease (arthritis, uveitis, erythema nodosum, pyoderma gangrenosum, primary sclerosing cholangitis), so symptoms overlap. The discriminator is depth and distribution on endoscopy and biopsy: transmural skip lesions with possible perianal disease, fistulas, or abscesses is Crohn; continuous mucosal disease starting at the rectum is UC. Colon cancer surveillance is needed in both, but the risk is higher in long-standing pancolitis UC.