Ischemic Intestinal Injury
GENERAL PRINCIPLES
Acute mesenteric ischemia results from arterial (or rarely venous) compromise to the superior mesenteric circulation.
Emboli and thrombus formation are the most common causes of acute mesenteric ischemia, although nonocclusive mesenteric ischemia from vasoconstriction can also give rise to the disorder.
Ischemic colitis results from mucosal ischemia in the inferior mesenteric circulation during a low-flow state (hypotension, arrhythmias, sepsis, aortic vascular surgery), often in patients with atherosclerotic disease.107 Vasculitis, sickle cell disease, vasospasm, and marathon running can also predispose to ischemic colitis.
Chronic mesenteric ischemia is caused by atherosclerosis of all three major abdominal arteries leading to intermittent hypoperfusion.
DIAGNOSIS
Clinical Presentation
Patients with acute mesenteric ischemia may present with abdominal pain, but physical examination and imaging studies can be unremarkable until infarction has occurred. As a result, diagnosis is often late and mortality is high.
Ischemic colitis typically presents with sudden abdominal cramping with an urge to defecate, followed by passage of bright red blood per rectum in 24 hours. Severe insults can lead to gangrene, perforation, and stricture formation.
Chronic mesenteric ischemia can present with abdominal pain after eating and weight loss from food avoidance.
Diagnostic Testing
Urgent angiography is indicated if the suspicion for acute mesenteric ischemia is high.
CT with IV contrast should be performed for suspected colonic ischemia, to evaluate for bowel wall thickening in watershed areas. Multiphasic CT angiography should be performed if acute mesenteric ischemia is suspected.107 Pneumatosis or portal venous gas indicates transmural infarction and necessitates surgical consultation.
In patients with ischemic colitis, characteristic thumb-printing of the involved colon may be seen on plain radiographs of the abdomen.
Colonoscopy with minimal insufflation should be performed to confirm the diagnosis.107 It may reveal mucosal erythema, edema, and ulceration, sometimes in a linear configuration; evidence of gangrene or necrosis is an indication for surgical intervention.
CT angiography or Doppler ultrasound can show stenosis of the abdominal vasculature in suspected chronic mesenteric ischemia.
TREATMENT
Treatment of acute mesenteric ischemia is essentially surgical and increasingly endovascular.107
In patients with ischemic colitis, in the absence of peritoneal signs or evidence of gangrene or perforation, expectant management with fluid and electrolyte repletion and maintenance of stable hemodynamics usually suffices. Broad-spectrum antimicrobials should be used in moderate to severe cases. Evidence of gangrene or necrosis is an indication for surgery.
Open and endovascular approaches are available for chronic mesenteric ischemia.108 Atherosclerosis of the mesenteric vessels without symptoms should be treated with risk-factor modification (see Chapter 4, Ischemic Heart Disease).