Curriculum · Gastroenterology
Crohn disease
What it is
IBD comprises a group of related conditions characterized by idiopathic inflammation of the GI tract, and the two most common are Crohn's disease and ulcerative colitis, both of which cause macroscopic inflammation. Crohn's disease can involve any part of the GI tract: small bowel with colon in 50%, small bowel only in 30%, and colon only in 20%. The involvement is transmural, with skip lesions. Several features may differentiate it from ulcerative colitis, but the overlap is significant.
Causes and risk
Smoking is a risk factor for the disease, while in ulcerative colitis smoking alleviates symptoms.
How it presents
Abdominal pain is prominent, with diarrhea, inflammatory masses, fever, weight loss, and intestinal strictures and fistula to skin, bladder, vagina, or enteric-enteric. The pain is post-prandial and colicky. Diarrhea is less prevalent than in ulcerative colitis, large in volume, watery, and usually non-bloody, though it may be bloody, particularly if there is distal colonic involvement. A palpable mass is frequent, in about 25%, in the RLQ. The most common extraintestinal manifestations are oral aphthous ulcers, arthralgia, and back pain indicating ankylosing spondylitis or sacroiliitis; eye redness, pain and swelling may result from uveitis or scleritis; skin manifestations include pyoderma gangrenosum and erythema nodosum; and liver involvement most commonly includes PSC.