Ulcerative colitis.

limited to the mucosa and submucosa

begins in the rectum and extends proximally in a continuous fashion

migratory polyarthritis, sacroiliitis, ankylosing spondylitis, uveitis, erythema nodosum, and hepatic involvement (pericholangitis and primary sclerosing cholangitis

Differences from Crohn’s disease

Well-formed granulomas are absent.

There are no skip lesions.

The mucosal ulcers rarely extend below the submucosa.

Mural thickening does not occur

high risk of carcinoma development

Morphology of UC:

rectum and sigmoid are invariably involved and may involve the entire colon-pancolitis

hyperemia, edema, and granularity with friability and easy bleeding

islands of regenerating mucosa bulge upward to create pseudopolyps

pericolonic abscess formation

Exposure of the muscularis propria and neural plexus to fecal material also may lead to complete shutdown of neuromuscular function-toxic megacolon

M/E

A diffuse, predominantly mononuclear inflammatory infiltrate in the lamina propria

crypt abscesses due to neutrophils

In late stages, granulation tissue fills in the ulcer craters, followed by regeneration of the mucosal epithelium

Submucosal fibrosis and mucosal architectural disarray and atrophy remain

Clinical features and complications:

mucoid diarrhea that may persist for days, weeks, or months and then subside, only to recur

Complications

severe diarrhea and electrolyte derangements

massive hemorrhage

severe colonic dilation (toxic megacolon) with potential rupture

perforation with peritonitis

Inflammatory strictures of the colorectum-must be differentiated from cancer.

sequential mucosal changes from dysplasia to invasive carcinoma- surveillance with repeated colonoscopies and multiple biopsies aimed at detecting dysplasia for possible prophylactic colectomy.

Crypt Abscess

Toxic Megacolon