Ischemic Colitis

Ischemic colitis usually begins with a temporary fall in blood flow to the colon rather than a fixed arterial blockage. The usual pattern is sudden cramping abdominal pain—often left-sided—followed by urgency and a small amount of bright red or maroon blood or bloody diarrhea within about 24 hours. Most episodes remain limited to the mucosa and improve with supportive care. The finding that changes the nurse’s urgency is evidence that ischemia may be progressing through the bowel wall. Constant or severe pain, guarding or rebound, hypotension, tachycardia, metabolic acidosis, rising lactate, right-sided or pancolonic involvement, or abdominal pain without rectal bleeding raises concern for gangrene, perforation, or acute mesenteric ischemia. These patients require immediate escalation rather than routine observation. Severe rectal bleeding requiring transfusion is also atypical and should prompt evaluation for another source.