Crohn’s disease
Definition
Crohn’s disease is a chronic, relapsing inflammatory disorder of the gastrointestinal tract. It may affect any segment from mouth to anus but classically involves the terminal ileum and colon. Inflammation is patchy (“skip lesions”) and transmural, causing complications-strictures, fistulae, abscesses and adhesions-that distinguish it from ulcerative colitis.
Epidemiology
- Typical onset: late adolescence to early adulthood.
- Distribution of involvement: terminal ileum ~45%, colon ~32%, ileum + colon ~19%, upper GI ~4%.
Pathophysiology and consequences
- Likely multifactorial: genetic susceptibility with environmental triggers.
- Transmural granulomatous inflammation leads to deep linear ulcers, mucosal cobblestoning, creeping fat and fibrofatty proliferation.
- Healing with fibrosis and penetrating disease explains strictures, obstruction, entero‑enteric/enterocutaneous fistulae and intra‑abdominal or perianal abscesses.
Risk factors
- Family history.
- Cigarette smoking (increases disease risk, relapse rates and likelihood of surgery).
- Prior infectious gastroenteritis.
- Recent appendicectomy (transiently increased risk).
- NSAID use.
- Combined oral contraceptives.