Ischemic colitis (ischaemic colitis in British English) is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater frequency in the elderly, and is the most common form of bowel ischemia. Causes of the reduced blood flow can include changes in the systemic circulation (e.g. low blood pressure) or local factors such as constriction of blood vessels or a blood clot. In most cases, no specific cause can be identified.
Ischemic colitis is usually suspected on the basis of the clinical setting, physical examination, and laboratory test results; the diagnosis can be confirmed via endoscopy or by using sigmoid or endoscopic placement of a visible light spectroscopic catheter (see Diagnosis). Ischemic colitis can span a wide spectrum of severity; most patients are treated supportively and recover fully, while a minority with very severe ischemia may develop sepsis and become critically, sometimes fatally, ill.
Patients with mild to moderate ischemic colitis are usually treated with IV fluids, analgesia, and bowel rest (that is, no food or water by mouth) until the symptoms resolve. Those with severe ischemia who develop complications such as sepsis, intestinal gangrene, or bowel perforation may require more aggressive interventions such as surgery and intensive care. Most patients make a full recovery; occasionally, after severe ischemia, patients may develop long-term complications such as a stricture or chronic colitis.
- A hyperactive phase occurs first, in which the primary symptoms are severe abdominal pain and the passage of bloody stools. Many patients get better and do not progress beyond this phase.
- A paralytic phase can follow if ischemia continues; in this phase, the abdominal pain becomes more widespread, the belly becomes more tender to the touch, and bowel motility decreases, resulting in abdominal bloating, no further bloody stools, and absent bowel sounds on exam.
- Finally, a shock phase can develop as fluids start to leak through the damaged colon lining. This can result in shock and metabolic acidosis with dehydration, low blood pressure, rapid heart rate, and confusion. Patients who progress to this phase are often critically ill and require intensive care.
Symptoms of ischemic colitis vary depending on the severity of the ischemia. The most common early signs of ischemic colitis include abdominal pain(often left-sided), with mild to moderate amounts of rectal bleeding. The sensitivity of findings among 73 patients were:
- abdominal pain (78%)
- lower digestive bleeding (62%)
- diarrhea (38%)
- Fever higher than 38°C (34%) (38°C equals approximately 100.4°F)
- abdominal pain (77%)
- abdominal tenderness (21%)
Ischemic colitis is often classified according to the underlying cause. Non-occlusive ischemia develops because of low blood pressure or constriction of the vessels feeding the colon; occlusive ischemia indicates that a blood clot or other blockage has cut off blood flow to the colon.
In hemodynamic unstable patients (i.e. shock) the mesenteric perfusion may be compromised. This condition is commonly asymptomatic, and usually only apparent through a systemic inflammatory response.
In addition, ischemic colitis is a well-recognized complication of abdominal aortic aneurysm repair, when the origin of the inferior mesenteric artery is covered by the aortic graft. Thus, patients without adequate collateralization are at risk for ischemia of the descending and sigmoid colon. Bloody diarrhea and leukocytosis in the postoperative period are essentially diagnostic of ischemic colitis.