188. Dysentery: etiology. Pathogenesis, morphological characteristics, intestinal complications, and their outcomes.

Dysentery is an acute intestinal infectious disease with predominant damage to the colon and intoxication.

Pathogenesis:

Bacteria develop into the epithelium of the colon, where they are inaccessible to white blood cells, antibodies, and antibiotics.  Cytopathic effect of shigella development of desquamative catarrh of the colon  release of enterotoxin during epithelial death  vasoneuroparalytic effect (paralysis of blood vessels, damage to intramural nerve ganglia of the Intestine).  fibrinous inflammation  development of ulcers.

Morphological characteristics:

Local changes develop mainly in the mucous membrane of the rectum and sigmoid colon. The degree of these changes towards the caecum decreases. There are 4 stages in the development of colitis: catarrhal colitis, fibrinous colitis, ulceration (ulcerative colitis) and ulcer healing.

The stage of catarrhal colitis (duration is 2-3 days) is characterized by hyperemia and swelling of the intestinal mucosa, in which there are areas of superficial necrosis and hemorrhage. The lumen of the intestine is narrowed due to muscle spasm. Microscopically, peeling of the epithelium is detected, in the cytoplasm of which shigella, hyperemia, edema, hemorrhages and foci of necrosis of the mucous membrane, leukocyte infiltrates in the stroma are found.

In the stage of fibrinous, more often diphtheria colitis (duration 5-10 days), a brown–green fibrinous film appears on top of the folds of the mucous membrane and between them. The intestinal wall is thickened, the lumen is sharply narrowed.

Histological examination shows mucosal necrosis penetrating to various depths, necrotic masses are permeated with fibrin filaments. The mucous membrane on the periphery of necrotic foci and the submucosal layer are edematous, infiltrated by leukocytes with foci of hemorrhage.

The stage of ulceration, i.e. ulcerative colitis, appears on the 10th-12th day of the disease. Ulcers of irregular shapes and different depths are formed primarily in the rectum and sigmoid colon due to the rejection of fibrinous films and necrotic masses. The possibility of bleeding and perforation of the intestinal wall is associated with the formation of ulcers.

The healing stage of ulcers is characterized by regeneration, which lasts for 3-4 weeks of the disease. The defects of the mucous membrane are filled with maturing granulation tissue. With minor defects, regeneration is complete, with deep and widespread destruction of the mucous membrane, scars form, leading to narrowing of the intestinal lumen. Sluggish healing of ulcers is possible, while pseudopolypes of the mucous membrane appear

Intestinal complications:

Perforation (microperforation) of the ulcer with the development of paraproctitis or peritonitis, intestinal phlegmon, less often — intracellular bleeding, cicatricial intestinal stenosis – are primarily associated with ulcers of the colon.

Outcomes: recovery, formation of bacterial carrier, transition to chronic forms, fatal outcome.