Ischemic Colitis

Ischemic colitis is the most common form of intestinal ischemia and the leading cause of acute lower GI bleeding in older adults. It results from a transient reduction in colonic blood flow, often without an identifiable thromboembolic source. Risk factors include hypotension, atrial fibrillation, vasoactive medications, recent cardiac or vascular surgery, and chronic kidney disease.

The anatomic distribution reflects the colonic blood supply. Two watershed areas — the splenic flexure (Griffith's point, between the SMA and IMA) and the rectosigmoid junction (Sudeck's point, between the IMA and the superior rectal artery) — are the most vulnerable. Right-sided ischemic colitis is less common but carries a worse prognosis and is more likely to require surgery.

The endoscopic spectrum runs from mild mucosal edema and petechiae through segmental ulceration to gangrenous, necrotic mucosa. Sparing of the rectum is the rule because of its dual blood supply. Diagnosis is clinicoendoscopic; biopsy can support the diagnosis but is rarely definitive. Most patients recover with bowel rest, IV fluids, and broad-spectrum antibiotics. Surgical consultation is needed for full-thickness necrosis, peritonitis, or recurrent disease.