Crohn disease
Meaning of Crohn disease: Full-thickness, patchy inflammation is what separates it from ulcerative colitis, and it explains the fistulas and narrowings that follow.
Definition of Crohn disease
Crohn disease is a long-term inflammatory bowel disease that can affect any part of the digestive tract from mouth to anus, most often the last part of the small intestine and the colon. The inflammation runs through the full thickness of the bowel wall and skips along it, leaving diseased segments between healthy ones.
How is it different from ulcerative colitis?
| Crohn disease | Ulcerative colitis | |
|---|---|---|
| Where | Anywhere from mouth to anus, most often the end of the small intestine | Colon and rectum only |
| Depth | Through the whole bowel wall | Confined to the inner lining |
| Pattern | Patchy, with normal bowel between diseased segments | Continuous from the rectum upward |
| Typical complications | Narrowings, fistulas, abscesses, disease around the anus | Severe bleeding, and dilation of the colon in severe attacks |
| Smoking | Associated with worse disease | Appears to reduce risk, which does not make it safe |
Both belong to the group called inflammatory bowel disease, and in a minority of cases affecting only the colon the two cannot be told apart at first. Neither is the same as irritable bowel syndrome, which produces symptoms without inflammation or damage to the bowel.
What does it do?
Abdominal pain, often in the lower right, and diarrhea are the usual features, sometimes with blood, along with weight loss, poor appetite and fatigue out of proportion to the bowel symptoms. Children may show slowed growth before anything else. Mouth ulcers, painful red eyes, joint pain and skin lesions occur outside the gut and can arrive first. Disease around the anus, with tags, fissures, abscesses and fistulas, is characteristic and is sometimes the presenting problem. Symptoms come in flares separated by quieter periods, and the pattern varies enough between individuals that two people with the same diagnosis may describe entirely different illnesses.
What follows from inflammation running so deep?
Because the whole wall is involved, repeated healing lays down scar that narrows the channel, producing a stricture and eventually obstruction. Inflammation can also tunnel outward, forming a fistula, an abnormal connection between bowel and another loop of bowel, the bladder, the vagina or the skin, or collecting as an abscess. Disease in the last part of the small intestine impairs absorption of vitamin B12 and bile salts, so deficiency and diarrhea can persist even when inflammation is controlled. Long-standing disease of the colon carries an increased risk of bowel cancer, comparable to that seen in ulcerative colitis, which is why surveillance is part of long-term care.
Also known as
Used in a sentence
The gastroenterologist reviewed the colonoscopy findings consistent with a flare of Crohn disease.
Good to know
Crohn disease can affect any segment of the digestive tract and involves the full thickness of the bowel wall, which distinguishes it from ulcerative colitis, a related condition confined to the colon and its inner lining.