- Acute mesenteric ischemia is a relatively rare clinical entity, but when diagnosis is delayed, it is almost always fatal; therefore, a high index of suspicion is required, especially in those at high risk: the elderly, those with cardiac dysfunction, patients with diffuse atherosclerosis, and those following aortic and cardiac surgery or arterial catheterization.
- The etiology of acute mesenteric ischemia may be embolic, thrombotic, primary vasoconstrictive, or secondary to venous thrombosis. Chronic ischemia is usually due to flow-limiting lesions (stenoses or occlusions) in the presence of inadequate collateralization.
- Classic symptoms of acute intestinal ischemia are central abdominal pain (often out of proportion to the benign abdominal examination), weight loss (an important clue even in the acute presentation), bowel emptying, and altered bowel function (vomiting, bloating, constipation, or diarrhea). Once signs of peritonitis or bloody diarrhea present, shock, sepsis, and death almost always follow.
- Mesenteric angiography is the investigation of choice, offering diagnostic and therapeutic options, whereas computed tomographic (CT) angiogram and duplex ultrasonography may not be definitive. Frequently, the diagnosis is confirmed only at laparotomy.
- Treatment is surgical, with restoration of flow by bypass or embolectomy, resection of nonviable intestine, and liberal use of “second look" laparotomy.
Acute mesenteric ischemia is a relatively rare but often fatal clinical entity. Although little data exist on its true incidence, data from the Swedish Vascular Registry suggest that it may account for just 1 percent of reconstructions for acute thromboembolism.1 Contemporary series, however, continue to report a mortality rate of between 32% and 48%.2,3 Although autopsy studies suggest that atherosclerosis affecting the mesenteric arteries is common (6% to 10%),4 symptomatic mesenteric occlusive disease is rare. However, of patients presenting with acute mesenteric ischemia, one large series found that 43% had prior symptoms of chronic mesenteric ischemia.5 The spectrum of mesenteric ischemia includes occlusive disease secondary to atherosclerotic occlusion with thrombosis, embolism, mesenteric venous thrombosis, and nonocclusive mesenteric ischemia due to vasospasm (Table 86-1). At its most florid, it may present with mesenteric infarction, intestinal perforation, and septic circulatory collapse. This relatively rare but often fatal clinical entity must be considered early in the differential diagnosis of any patient with abdominal symptoms or signs but especially those with a history of intestinal angina, peripheral vascular disease, cardiac dysfunction, aortic surgery or recent aortic catherization, hypotension, or prothrombotic state. Noninvasive tests lack specificity and sensitivity, which indicates that the diagnosis often requires a high index of suspicion, supplemented by a liberal use of diagnostic arteriography (or computed tomographis angiogram) when uncertainty remains. Where doubt exists in the presence of emerging acute abdominal signs or clinical deterioration, diagnostic laparotomy is indicated. This discussion will focus on the etiology, pathophysiology, diagnosis, and management of acute mesenteric ischemia.
Table 86–1. Potential Causes of Acute Mesenteric Ischaemia