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Most common form of intestinal ischemia.
Referred to as ischemia with bowel infarction that may progress to necrosis and death.
The most common mechanism is an acute compromise in intestinal blood flow.
The three main mechanisms of ischemic colitis include nonocclusive ischemic colitis, embolic and thrombotic arterial occlusion, and mesenteric venous thrombosis.
Non-occlusive ischemic colitis is cause by hypoperfusion of the mesenteric microvasculature and is the most common mechanism, occurring in 95% of patients.
Non-occlusive colonic ischemia is most prominent at the watershed areas meaning the splenic flexure and rectosigmoid junction, however any segment of the colon can Be affected.
The rectum is not commonly involved because it has a dual blood supply from splanchnic and systemic arterial systems.
Presentation is usually with abdominal pain and tenderness over the involved bowel.
Passage of stool and blood usually is present, but bleeding is not usually hemodynamically significant.
Non-occlusive ischemic colitis is usually transit, however prolonging severe ischemia causes the necrosis of the mucosal layer with potential for transmural infarction.
Colon injury is related to hypoxemia during the episode of decreased blood flow and the sequelae of reperfusion, which is seen after partial ischemia.
Reperfusion results in the release of free oxygen radicals and other toxic products.
Can result, uncommonly, from arterial thromboemboli from mesenteric venous thrombosis which almost always involves the proximal colon.
Occurs in well-defined clinical settings, particularly in patients with vascular risk factors including: diabetes, coronary artery disease, and peripheral vascular disease.
Can occur without identify risk factors.
Colonoscopy is the diagnostic procedure of choice.
Abdominal CT scans can be suggestive of the diagnosis.
Treatment includes intravenous fluids, avoidance of vasoconstrictive agents, bowel rest, and use of antibiotics.
Most patients improve in 1-2 days.
20% of patients will require surgery with the development of peritonitis and clinical deterioration.