Ischemic colitis, also known as ischemic enteropathy, is a series of inflammatory reactions and injuries to the colon due to inadequate blood supply. It usually occurs in older adults over 50 years of age and can be caused by systemic diseases such as hypotension, or by narrowing or embolization of the local blood supply arteries to the intestine. In most cases, the exact cause is difficult to detect. Abdominal pain, diarrhea and blood are the main symptoms of acute ischemic colitis, called the “ischemic colitis triad”. The symptoms of ischemic colitis depend on the severity of the ischemia. The most common early symptoms of ischemic colitis include abdominal pain and mild to moderate rectal bleeding. Sensitivity of signs and symptoms: abdominal pain (78%), lower gastrointestinal bleeding (62%), diarrhea (38%), fever over 38°C (34%); signs: abdominal pain (77%), abdominal tenderness (21%). Etiologically, the causes of colonic ischemia can be broadly divided into two categories, one is vascular obstruction type, and the other is non-vascular obstruction type. 1, vascular obstruction type of colonic ischemia: mainly injury to mesenteric vessels, arteriosclerosis, mesenteric vessel embolism or thrombosis, surgical ligation of the inferior mesenteric artery during abdominal aortic reconstruction, etc. 2.Non-vascular obstruction type of colonic ischemia: Most of them are spontaneous, usually not accompanied by obvious vascular obstruction, and it is difficult to find a clear clinical cause of colonic ischemia. Most of these patients are elderly, and after the occurrence of ischemic changes in the colon, the vascular abnormalities shown by mesenteric angiography may not match the clinical symptoms. There are various causes that can induce spontaneous colonic ischemia, among which hypotension from various causes is the most common, such as infectious shock, cardiogenic shock, anaphylactic shock, neurological shock, etc. Concomitant heart disease, hypertension, diabetes mellitus and concomitant administration of medications that can affect visceral blood flow (such as antihypertensive drugs, etc.) can significantly increase the chance of colonic ischemia. Decreased mesenteric blood supply causes colonic ischemia; in turn, widespread acute mesenteric blood supply disorders can cause a significant irreversible decrease in cardiac output, thus leading to a vicious cycle of mesenteric ischemia. The pathological changes in ischemic colitis correlate with the clinical severity. In milder or early cases, there is mainly mucosal and submucosal hemorrhage and edema, possibly with minor necrosis or ulceration. In more severe ischemia, pathologic pictures resembling the manifestations of inflammatory bowel disease (i.e., chronic ulcers, crypt abscesses, and pseudopolyps) may be seen. In the most severe cases, infarction through the wall with its resulting perforation may be seen. Upon resuscitation, the muscularis propria may be replaced by fibrous tissue. The main manifestation on ultrasound is edematous thickening of the colonic wall, most commonly at the splenic flexure of the colon, as this is the junction area of the blood supply between the superior mesenteric artery and the inferior mesenteric artery, which is susceptible to ischemia. The thickening of the intestinal wall is usually more extensive. The thickened intestinal wall is dominated by highly echogenic mucosal edema, and the thickened edematous mucosa fills the intestinal lumen, resulting in a linear narrowing of the intestinal lumen with significant mesenteric edema thickening and echogenic enhancement. The color Doppler ultrasound showed stellate blood flow signals in the thickened intestinal wall. Other lesions with more extensive thickening of the colonic wall on ultrasound include ulcerative colitis and pseudomembranous enterocolitis. It is not difficult to differentiate them by combining history, involvement, age, and symptoms and signs.