Used to be called "terminal ileitis" or "regional enteritis”
extra-intestinal complications of immune origin, such as uveitis, sacroiliitis, migratory polyarthritis, erythema nodosum, primary biliary cirrhosis, and obstructive uropathy due to excess formation of calcium oxalate stones
Sharply limited transmural involvement of the bowel by an inflammatory process with mucosal damage
Presence of noncaseating granulomas
sharply delimited and transmural inflammation of the bowel with mucosal damage
The intestinal wall is rubbery and thick, due to edema, inflammation, fibrosis, and hypertrophy of the muscularis propria
lumen is almost always narrowed, seen radiographically as the "string sign,"
When several bowel segments are involved, the intervening bowel is essentially normal ("skip" lesions).
ulcers coalesce into long, serpentine linear ulcers, which tend to be oriented along the axis of the bowel- giving cobblestone appearance
adhesions with adjacent loops of bowel, fistula or sinus tract and abscess formation
inflammation, with neutrophilic infiltration into the epithelial layer and accumulation within crypts to form crypt abscesses
chronic mucosal damage in the form of architectural distortion, atrophy, and metaplasia
the muscularis mucosae and muscularis propria are usually markedly thickened, and fibrosis
dysplastic changes in long standing cases- predictors of adenocarcinoma
Clinical feature and complications:
chronic relapsing inflammatory disorders with recurrent episodes of diarrhea, crampy abdominal pain, and fever lasting days to weeks
fistula formation to other loops of bowel, the urinary bladder, vagina, or perianal skin
abdominal abscesses or peritonitis
intestinal stricture or obstruction,
massive intestinal bleeding,
toxic dilation of the colon, or
carcinoma of the colon or small intestine.