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Ischemic colitis (IC) results from decreased blood flow to the colon with resultant inflammation and tissue damage.
- More common in the elderly; can affect patients of all ages
- Patients present in several ways:
- Nonacute IC from a chronic process with irreversible ischemic injury
- Acute IC—self-limited transient mucosal ischemia
- IC is self-limited and reversible in 80% of patients:
- 20% of patients progress to full-thickness necrosis requiring surgical intervention.
- Most commonly, ischemia is related to a nonocclusive reduction in blood flow.
- Presentation varies, but patients with acute IC typically present with localized abdominal pain and tenderness. Frequent loose, bloody stools may be seen within 12 to 24 hours of onset.
- Laboratory and radiographic findings are nonspecific and must be correlated with clinical presentation.
- Colonoscopy is the gold standard for diagnosis of IC.
- In the absence of complications, most patients recover with supportive care including IV fluids, bowel rest, and clinical monitoring.
- Men and women are at equal risk.
- Evidence of IC seen in 1 of every 100 endoscopies
Rare in patients <60 years old. 70 years is the average age at diagnosis.
- 4.5 to 44 cases per 100,000 in the general population
- 1 of every 2,000 hospital admissions
- True incidence may be underestimated due to nonspecific clinical manifestations.
19 cases per 100,000 in the general population
Etiology and Pathophysiology
- Local hypoperfusion in the colon compromises the ability to meet metabolic demands. Reperfusion injury may also play a role.
- Most commonly, an acute, self-limited process
- The colon is perfused by both the superior and inferior mesenteric arteries (SMAs and IMAs) and branches of the internal iliac arteries. Occlusion of branches of the SMA or IMA rarely leads to ischemic consequences due to extensive collateral circulation.
- Watershed areas of the colon (splenic flexure and rectosigmoid junction) are most susceptible to ischemic damage. Blood is carried by narrow branches of the SMA and IMA to these areas, putting them at increased risk for ischemia. The splenic flexure is supplied by the terminal branches of the SMA, and the rectosigmoid junction is supplied by the terminal branches of the IMA.
- Left colon is more commonly affected than the right.
- The rectum is often spared because of additional blood supply from the internal iliac arteries.
- Poor perfusion may result from systemic disease, local vascular compromise, and anatomic or functional changes in the colon itself. An occlusion of large vessels is usually not identified.
- Hypoperfusion from shock, trauma
- Embolic occlusion of mesenteric vessels
- Hypercoagulable states, vasculitis
- Sickle cell disease
- Arterial thrombosis; venous thrombosis
- Mechanical obstruction of the colon (e.g., tumor, adhesions, hernia, volvulus, prolapse, diverticulitis)
- Surgical complications
- Medications (intestinally active vasoconstrictive substances, medications that induce hypotension and thus, hypoperfusion)
- Cocaine abuse
- Aortic dissection
- Strenuous physical activity (e.g., long-distance running)
- Repeated episodes of ischemia and inflammation may result in chronic colonic ischemia, possible stricture formation, recurrent bacteremia, and sepsis. These patients may have unresolving areas of colitis and require segmental colonic resection.
- Age >60 years (90% of patients)
- Smoking (most common cause of recurrent IC) (1)
- Hypertension, diabetes mellitus (1)
- Rheumatologic disorders/vasculitis
- Cerebrovascular disease, ischemic heart disease (1)
- Recent abdominal surgery
- Constipation-inducing medications (1)
- History of vascular surgery (1)
- History of ileostomy
- Chronic obstructive pulmonary disease
- Hypoalbuminemia; hemodialysis
- Hypercoagulability, oral contraceptive (1)
- AAA repair (IMA ligation) (1)
- IBS (1)