Crohn’s disease.

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

Hallmarks are

Sharply limited transmural involvement of the bowel by an inflammatory process with mucosal damage

Presence of noncaseating granulomas

Fistula formation

Gross morphology:

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

Microscopic feature:

inflammation, with neutrophilic infiltration into the epithelial layer and accumulation within crypts to form crypt abscesses

Ulceration

chronic mucosal damage in the form of architectural distortion, atrophy, and metaplasia

the muscularis mucosae and muscularis propria are usually markedly thickened, and fibrosis

Lymphoid aggregates

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

Complications

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.