1. Acute ischemic bowel disease
Schematic of the three levels of severity, diagrammed for the small intestine.

2. Gangrene small intestine
Infarcted small bowel, secondary to acute thrombotic occlusion of the superior mesenteric artery.

3. Ischemic enteritis
The mucosa demonstrates marked hyperemia as a result of ischemic enteritis.
At closer view, early ischemic enteritis (or colitis) involves the tips of the villi. In general, bowel is hard to infarct from atherosclerotic vascular narrowing or thromboembolization because of the widely anastomosing blood supply. Thus, most cases of ischemia and infarction result from generalized hypotension and decreased cardiac output.

4. Ischemic colitis showing a highly hyperemic surface with ulceration
Ischemic colitis. The lesion is typically located in the splenic flexure. The mucosa is markedly hyperemic and covered by a fibrinopurulent exudate.
Ischemic colitis showing a highly hyperemic surface with ulceration

5. Ischemic entritis; mucosal necrosis
With more advanced necrosis, the small intestinal mucosa shows hemorrhage with acute inflammation in this case of ischemic enteritis.

6. Acute ischemic colitis
The upper mucosa is necrotic and degenerated with eosinophilic hyalinazation, inflammation and edema of the lamina propria. The lower mucosa shows loss of crypts but with evidence of regeneration Kryptenepithel abgeschilfert and degenerates. Lower Kryptenepithel regenerated with Becher cell loss. Eosinophilic hyalines edema of the Tunica propria. There is an overlying pseudomembrane