Thursday 28 June 2012

Pathogenesis

Pathophysiology

Ulcerative Colitis

    Photobucket
  • It begins in the rectum (proctitis) and spreads proximally along the entire colon (pancolitis) in a continuous fashion.
  • The mucosa of the rectum and the colon is hyperemic and edematous in the affected area.
  • Multiple abscesses develop in the crypts of Lieberkuhn (intestinal glands).
  • As the disease advances, the abscesses break through the crypts into the submucosa, leaving ulcerations.
  • These ulcerations destroy the mucosal epithelium, causing bleeding and diarrhea – the loss of fluid and electrolytes caused by the decreased mucosal surface are for absorption.
  • Protein loss through the stool is also evidenced due to breakdown of cells.
  • Areas of inflamed mucosa can form pseudopolyps, tonguelike projections into the bowel lumen.
  • Granulation tissue develops, and the mucosa musculature becomes thickened, shortening the colon.

Crohn’s Disease

  • PhotobucketIt is characterized by inflammation of segments of the GI tract.
  • It can affect any part of the GI tract
    • Most often seen in the terminal ileum and the colon.
    • Involvement of the esophagus, the stomach, or the duodenum is uncommon.
  • T-helper cell cytokines such as interleukin-12 and tumor necrosis factor (TNF) stimulate the inflammatory response, which begins in the intestinal submucosa and extends to all the layers of the bowel wall.
  • Activated neutrophils and macrophages promote inflammation and cause tissue injury.
  • The inflammation can affect some segments of the intestine but not others resulting in discontinuous skip lesions.
  • Ulcerations are deep and longitudinal and penetrate between islands of inflamed edematous mucosa, causing the classic cobblestone appearance.
  • Thickening of the bowel wall occurs, as well as narrowing of the lumen with stricture development – promotes obstruction.
  • Abscesses or fistula tracts that communicate with other loops of bowel, the skin, the bladder, the rectum or the vagina may develop.
  • Histologically, granulomas are present in 50% of clients and may be located in any layer of the bowel wall – giving the affected area a cobblestone appearance.
Previous Section: Pathogenesis                                      Home                                            Next Section:Clinical Manifestations

No comments:

Post a Comment