Causes of reduced blood flow leading to ischemic colitis include changes in the systemic circulation such as low blood pressure (hypotension) or local factors such as constriction of blood vessels, a blood clot, or drugs. In most cases, no specific cause can be identified.

The causes of ischemic colitis are as follows:^[1][2][3]

• 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 hemodynamically unstable patients the mesenteric perfusion can be compromised.

• Obstructive atherosclerotic disease
  • Superior mesenteric artery occlusion

• Thromboembolism
  • Most commonly the embolism is due to atrial fibrillation
  • Valvular heart disease including endocarditis
  • Myocardial infarction
  • Cardiomyopathy

• Hernia
• Tumor

The following drugs cause vasoconstriction which may compromise blood supply to the colon.

• Alosetron
• Cilansetron
• Interferon alfacon-1
• Pegylated interferon alfa-2b
• Ramosetron
• Vasopressors
• Ergotamine