BMJ 2003;326:1372; GE 2000;118:954

Cause: This catastrophic illness most commonly results from emboli, but it can also result from arterial or venous thrombi, low-flow states, or vasculitis.

Pathophys: Sudden occlusion of a mesenteric vessel causes ischemia that progresses to infarction, usually within 24 hr. About 50% of pts have arterial occlusion, 15% have venous occlusion, and the remainder have nonocclusive disease. This latter group often develops illness after systemic hypotension, CHF, or septic shock.

Sx: Pts develop severe abdominal pain that is often out of proportion to physical exam findings. There may be associated risk factors such as recent MI, CHF, hypercoagulable states, or evidence of preexisting chronic ischemia (postprandial pain). However, many pts have no associated risk factors.

Si: Early in the course of illness the abdominal exam may be relatively benign, but as ischemia worsens, tenderness increases, bowel sounds are lost, and peritoneal findings develop.

Diff Dx: Acute abdominal pain (p 4).

Crs: Mortality rate is high and varies with etiology. Operative mortality is greatest for arterial thrombosis (77%) and nonocclusive ischemia (73%). It is lower for arterial embolism (54%) and venous thrombosis (32%) (Brit J Surg 2004;91:17).

Lab: No single serum test is helpful in making the dx. CBC with differential, CMP (to look for other causes and evaluate the anion gap as a clue to metabolic acidosis), and amylase should be obtained to help in diff dx.

X-ray: Plain films are used to exclude free air requiring immediate laparotomy. Doppler ultrasonography can evaluate the proximal portions of the celiac, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA), but occlusions can be asymptomatic, making the test less valuable in the acute setting. CT can show abnormalities late in the course of illness caused by SMA emboli (such as gas in bowel wall, thickened bowel, or portal venous gas), but it is insensitive prior to infarction. CT is more helpful in identifying mesenteric vein occlusions. Mesenteric angiography is the diagnostic gold standard, but experts disagree on its routine use in suspected mesenteric ischemia. Proponents of angiography in suspected
AMI cite the many negative results that save a laparotomy and the positives that allow for early dx. Opponents cite delays in dx from lack of ready availability and the time it takes to perform the test. Local expertise will play a big role. Angiography can show embolus (either partially or completely occluding) either in the major vessels or in distal branches. It may also show evidence of nonocclusive mesenteric ischemia (NOMI), in which no occlusion is seen but there is intense microvascular vasoconstriction (Am J Surg 1996;171:405).

Endoscopy: Not indicated.

Rx: Those with suspected mesenteric ischemia and no availability of angiography go to laparotomy as do those with peritoneal signs. Rx of pts with positive angiograms depends on the finding. Major emboli are treated with embolectomy, and thrombus is treated with bypass (Arch Surg 1999;134:328), though surgery may be obviated by thrombolysis in some cases (J Vasc Interv Radiol 2005;16:317). Infarcted segments are resected and a second-look operation may be needed to reassess viability of the remaining bowel (Arch IM 2004;164:1054). Minor emboli (in smaller distal vessels) can be treated with thrombolytics, papaverine, or anticoagulation. Superior mesenteric vein thrombus without peritoneal signs can be treated with anticoagulation. Such pts should be evaluated for a hypercoagulable state. Nonocclusive mesenteric ischemia can be treated with intra-arterial papaverine.

BMJ 2003;326:1372; GE 2000;118:954

Cause: Vascular thrombosis from atherosclerotic disease.

Pathophys: Most pts (90%) have severe stenosis or occlusion of 2 or 3 of their mesenteric vessels. They are unable to increase gut blood flow in response to food. A small minority have occlusions of SMA (7%) or celiac (2%) alone.

Sx: Pts develop pain 1-3 hr after meals that persists 1-3 hr, and sx occur with increasing frequency over weeks to months. The pain, aka abdominal angina, creates a fear of eating and subsequent weight loss.