Ischemic colitis causes

Causes
Ischemic colitis is often classified according to the underlying cause. Non-occlusive ischemia develops because of low blood pressure or constriction of the vessels supplying blood to the colon; occlusive ischemia indicates that a blood clot or other blockage has cut off blood flow to the colon. In most cases, no specific cause can be identified.

Non-occlusive ischemia
In hemodynamically unstable patients (i.e. shock patients) the mesenteric perfusion may be compromised.

Occlusive ischemia
Occlusive is ischemia is due to either:

1. Obstructive Atherosclerotic Disease
 * Superior mesenteric artery occlusion

2. Thromboembolism:
 * Most commonly the embolism is due to atrial fibrillation
 * Valvular heart disease including endocarditis
 * Myocardial infarction
 * Cardiomyopathy

Drugs

 * Alosetron
 * Cilansetron
 * Ramosetron