Inflammatory bowel disease with chronic transmural inflammation of alimentary track marked by noncaseating granulomas and Òskip areasÓ; most common sites of inflammation are terminal ileum and colon, with additional involvement of skin, eyes, and joints (25% of cases affect small bowel only, and 25% affect colon only). Fistulas between bowel loops are common; also found are abdominal cramps, nonbloody diarrhea, perforation, and perianal abscesses. Transmural inflammation and granulomas are pathognomonic; on contrast studies, mucosa shows cobblestone appearance due to deep linear ulcers; most common complication is obstruction. Condition is most common surgically treated disease of small bowel. Medical treatment is optimized (bowel rest, antibiotics, steroids) before surgery is considered. Bowel resection margins are to grossly normal bowel; 50% recurrence rate of significant disease after resection. CrohnÕs patients have 75 times greater risk of adenocarcinoma of small bowel with poorer prognosis (and increased risk of bladder cancer) than non-CrohnÕs patients. Primary drug treatment uses corticosteroids for active disease, with response rates of 75%Ð90%.