Bowel Ischemia

Bowel ischemia can affect a small or large intestine and can occur by any cause, which leads to intestinal blood flow reduction.[1] This is an uncommon medical condition, but it has a high mortality rate.[2] The intestine is mainly supplied by 2 major arteries, which include the superior mesenteric artery (SMA) and the inferior mesenteric artery (IMA). The SMA supplies the bowel from the lower part of the duodenum to two-third of the transverse colon. The IMA supplies a large intestine from the distal one-third of the transverse colon to the rectum. The celiac artery also has collaterals to supply the intestine.[3] Bowel ischemia can be classified as small intestine ischemia, which is commonly known as mesenteric ischemia[4] and large intestine ischemia, which generally referred to as colonic ischemia.[5] Two main areas in the colon, including splenic flexure (Griffiths point) and rectosigmoid junction (Sudek's point), are prone to ischemia. These are also known as the 'watershed' areas, which mean the regions in the colon between 2 major arteries that supplying colon. Splenic flexure is the area between SMA and IMA supplies, and the rectosigmoid junction is the region between the IMA and the superior rectal artery supplies.[6][7]These areas mostly supplied by the marginal artery; however, in 50% of the population, this artery is poorly developed. Watershed areas account for about 70% of ischemic colitis cases. The colon venous drainage is the parallel of arterial supply. The superior mesenteric vein drains the areas supplied by SMA, and an inferior mesenteric vein drains the left side of the colon and the rectum.[5] An acute decrease in mesenteric arterial blood flow accounts for 60% to 70% of patients with mesenteric ischemia. The rest of the causes are related to colonic ischemia and CMI.[8] Abdominal pain is the most common symptom in patients with intestinal ischemia. Some features of a patient can help to distinguish between the acute small bowel and colonic ischemia. Patient's characteristics, such as age over 60 years, not appearing severe ill, mild abdominal pain, tenderness, rectal bleeding, or bloody diarrhea, are the features that are more common in acute colonic ischemia.[9] Generally, an abdominal computed tomography (CT) scan is used in hemodynamically stable patients who present with acute abdominal pain.[10][11] In patients with high suspicious for intestinal ischemia, CT angiography and MR angiography are the initial tests.[12] Based on acute mesenteric ischemia (AMI) subtypes, different medication treatments have been suggested. Papaverine, through the angiographic catheter with the mechanism of relaxation of vessels vasospasm, can be used for all arterial forms of AMI and nonocclusive mesenteric ischemia.[13][14][15]