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PATIENT STORY

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A 74-year-old hypertensive male presents with a four-hour history of acute-onset severe diffuse abdominal pain. Two weeks prior he was hospitalized with a large anterior wall MI complicated by intermittent atrial fibrillation. Due to a history of frequent falls, he was not anticoagulated. Physical examination is remarkable for an uncomfortable individual with an irregularly irregular heart rhythm and a minimally tender abdomen without peritoneal signs. Laboratory assessment is remarkable for a leukocytosis of 14,000 and mild metabolic acidosis. Electrocardiography indicates atrial fibrillation with a rapid ventricular response between 120 and 140 beats/minute. CT scan of the abdomen illustrates a distended small bowel and a questionable filling defect within the superior mesenteric artery (SMA). Mesenteric arteriography displays a "mercury meniscus sign" within the SMA 4 cm from the aorta. A diagnosis of cardioembolic acute mesenteric ischemia is made and the patient is immediately taken to the operating suite.

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EPIDEMIOLOGY

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  • Incidence: 3 to 5 per 100,000.

  • Sixth to seventh decade of life; more often women.

  • Etiology: thromboembolism 50%, thrombosis 20%, nonocclusive mesenteric ischemia (NOMI) 20%, others 10%.1

  • Clinical presentation depends on adequacy of visceral perfusion by the three mesenteric arteries: celiac artery (CA), superior mesenteric artery (SMA), and inferior mesenteric artery (IMA) (Figure 45-1). There are usually collateralizations among the mesenteric arteries that compensate for flow if there are stenoses or occlusions, hence the common adage; two of the three mesenteric arteries need to be involved before symptoms arise. However, single mesenteric artery occlusion can be symptomatic in the absence of adequate collateralization, such as in acute thromboembolism.

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FIGURE 45-1

Normal mesenteric artery anatomy, their branches and natural collateralization. Celiac artery (CA), superior mesenteric artery (SMA), inferior mesenteric artery (IMA), common hepatic artery (CHA), splenic artery (SA), gastroduodenal artery (GDA), superior pancreaticoduodenal artery (SPDA), inferior pancreaticoduodenal artery (IPDA), left gastric artery (LGA), right gastric artery (RGA), right gastroepiploic artery (RGEP), left gastroepiploic artery (LGEP), jejunal arteries (JAs), middle colic artery (MCA), right colic artery (RCA), ileocolic artery (ICA), marginal artery of Drummond (MAD)—between left branch of MCA and ascending branch of left colic artery (LCA), sigmoidal artery (SgA), superior rectal artery (SRA).

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PATHOPHYSIOLOGY

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Thromboembolism

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  • Thromboembolism to the SMA is common due to its obtuse angle and path, diverging gently away from the aorta and its flow.

  • Embolus source: cardiac arrhythmias (atrial or ventricular), atherosclerotic aorta, proximal thoracic aneurysms. Proximal small intestines may be uninvolved if embolus occludes the SMA a few centimeters beyond its origin, sparing proximal jejunal branches. Transverse colon may be spared if occlusion is beyond the middle colic branch of the SMA.

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Thrombosis

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  • Patients are generally older and usually women.

  • Evidence of atherosclerotic disease in other vascular beds (coronary, lower extremities) is usually present.

  • More than ...

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