Diverticulitis pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2], Ahmed Elsaiey, MBBCH [3] James Nasr[4]

Diverticula are sac-like protrusions of the mucosal and submucosa through weak points in the muscular wall, and occur more commonly in the sigmoid colon. Diverticulitis is the inflammation of a diverticulum. The first steps in the pathogenesis of diverticulitis are an increase in intraluminal pressure, change in intestinal motility, and bacterial colonization.^[1] The inflammation is caused by histamine, tumor necrosis factor, and metalloproteinases, which have been found in diverticulitis patients’ tissue biopsies. Obstruction of the diverticula leads to bacterial colonization, which causes inflammation.

The pathogenesis of diverticulitis is believed to be erosion of the wall of the diverticulum. It is worsened by an increase in intraluminal pressure or food remnants.

• Diverticula are protrusions of the mucosa and serosa intestinal layers and occur more often on the left side than the right side. Diverticulitis is the inflammation of this protrusion.

• Inflammation and focal necrosis ensue, resulting in perforation and inflammation.^[2]
• The pathogenesis of diverticulitis includes three main processes, which are:
  • Change in the intestinal motility
  • Increase in the luminal pressure
  • Secondary infection may be caused by colonic microbial flora^[3]
• In vivo tests showed that adding chemicals to the colonic tissue can lead to diverticulitis. Neuro-alteration of the tissue was noticed during this test. It showed increased contractility and loss of relaxation.^[4] This alteration in the muscle tissue due to inflammation leads to histological changes of the muscle and nerves.
• Inflammation in cases of diverticulitis is caused by histamine, tumor necrosis factor, and matrix metalloproteinases. These substances were detected in colonic tissue biopsies of diverticulitis patients.^[5]
• The collection of feces and undigested food in the diverticula leads to diverticulum obstruction. This obstruction, by increasing intraluminal pressure, leads to diverticulum distension and collection of the bacteria that cause inflammation.
• The presence of lymphocytes and granulomas are predictive of chronic inflammation.

The gross pathology of diverticulitis includes features such as:^[6][7]

• Corrugated – like cardboard
• Wall thickening (reactive)
• Located usually in the sigmoid colon
• May be found in the appendix

The possible histopathological findings of diverticulitis may include the following:

• Abscess at which neutrophils, lymphocytes, and fibrosis are observed.
• Sulfur granules with peripheral inflammatory cells.

• A brief video showing histopathological findings in patients with diverticulitis:

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