Expansion
Transmural granulomatous inflammation versus mucosal crypt abscesses
Expansion
| Feature | Crohn disease | Ulcerative colitis |
|---|---|---|
| Depth | Transmural | Mucosa and submucosa only |
| Distribution | Skip lesions, mouth to anus | Continuous from rectum |
| Granulomas | Non-caseating, in about a third | Absent |
| Crypt abscesses | Present | Prominent |
| Goblet cells | Preserved | Depleted |
| Macroscopic | Cobblestoning, deep fissuring ulcers, fat wrapping, strictures | Pseudopolyps, superficial ulceration, loss of haustra (lead pipe colon) |
| Complications | Fistulae, abscess, stricture, perforation | Toxic megacolon, massive haemorrhage |
Depth explains the complication profile: transmural inflammation reaches the serosa and adjacent structures, producing fistulae and abscesses; mucosal inflammation bleeds and, when severe, paralyses the colon into a toxic megacolon.
Malignant risk is substantial in longstanding extensive ulcerative colitis, related to duration and extent, and to coexisting primary sclerosing cholangitis. Surveillance targets dysplasia. Crohn colitis carries a similar risk in affected segments.
Smoking is protective in ulcerative colitis and harmful in Crohn disease, one of the few genuinely paradoxical associations in medicine.