Historical Background
Traditionally, the preferred treatment to restore adequate blood flow to the visceral organs was open surgical bypass. This treatment resulted in significant morbidity and mortality rates, ranging from 12% to 33% and 2% to 15%, respectively. In 1980 Furrer and colleagues were the first to report a successful angioplasty of a superior mesenteric artery stenosis. The role of percutaneous mesenteric revascularization has since expanded and in most circumstances has become the initial treatment of choice for chronic superior mesenteric artery occlusive disease. A recent examination of a nationwide database in the period between 2000 and 2006 that included 5583 chronic mesenteric ischemia patients estimated that 69% of patients with chronic mesenteric ischemia were treated by percutaneous transluminal angioplasty with or without stent placement (PTA/S). Despite a higher proportion of elderly patients with medical comorbidities undergoing PTA/S, mortality and morbidity rates were 3.7% and 20%, respectively, compared with 13% and 38%, respectively, after surgical bypass. Admittedly, endovascular treatment is associated with lower long-term patency and a greater likelihood of repeat interventions.
Indications
Chronic mesenteric ischemia is usually related to atherosclerosis, with symptoms occurring over a period of weeks to months. Postprandial intestinal angina appears when perfusion of visceral organs fails to meet normal metabolic requirements. A dull, colicky pain typically starts within 15 to 30 minutes of food intake and can persist 5 to 6 hours. The abdominal pain is commonly misdiagnosed as another gastrointestinal disorder.
Food phobia results in malnourishment, with an average weight loss of 20 to 30 pounds. In addition, stenotic arteries harbor a risk of atherosclerotic plaque rupture and focal thrombosis or embolization, which can result in acute mesenteric ischemia and bowel infarction. One third of patients with multiple mesenteric vessel involvement and symptoms may progress to acute mesenteric ischemia and intestinal infarction, with a mortality rate of more than 50%. Nonatherosclerotic causes of chronic mesenteric ischemia include radiation arteritis, chronic aortic dissection, fibromuscular dysplasia, median arcuate ligament syndrome, or vasculitis, such as Takayasu disease, Buerger disease,and polyarteritis nodosum. Most symptomatic patients have an atherosclerotic occlusion or more than 70% stenosis of the superior mesenteric artery combined with occlusion or stenosis of at least one other mesenteric vessel. Symptomatic mesenteric artery stenosis is an indication for intervention. Endovascular therapy is the preferred initial approach in patients with chronic mesenteric ischemia, whereas open revascularization is reserved for early or late failures. In principle, PTA/S also allows correction of malnourishment should subsequent open revascularization be required.
The presence of an asymptomatic mesenteric artery stenosis is not automatically associated with subsequent acute or chronic mesenteric ischemia and is a frequent finding among elderly patients. Asymptomatic disease of the celiac axis or superior mesenteric artery may be safely observed, and prophylactic intervention is not warranted. However, in certain circumstances, a symptomatic patients with significant three-vessel disease may benefit from revascularization, particularly if aortic or colonic resection is planned. That type of surgery can compromise the collateral vascular network and result in acute mesenteric ischemia.
Preoperative Preparation
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Patients experiencing postprandial pain and weight loss should have an extensive diagnostic workup to rule out other gastrointestinal disorders, including hepatobiliary disease and gastric, colonic, or pancreatic malignancy.
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The initial diagnostic study to evaluate for the presence of chronic mesenteric ischemia is a duplex flow study of the superior mesenteric artery ( Fig. 41-1 ). It is noninvasive and usually easy to perform because patients are often thin; however, bowel gas and arterial calcifications may limit accurate determination of flow velocity.
Figure 41-1
Duplex flow study of the superior mesenteric artery after stent placement. A, Color flow duplex imaging of the stent. B, B-mode imaging of the superior mesenteric artery ( arrowhead ) after stent placement.
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If the symptom complex and duplex findings are consistent with chronic mesenteric ischemia, an angiogram and intervention can be offered. Preoperative computed tomography (CT) angiography imaging can be obtained for procedure planning but is not mandatory ( Figs. 41-2 and 41-3 ). Major collateral pathways exist between the celiac artery and the superior mesenteric artery through the gastroduodenal and pancreaticoduodenal arcade, between the superior and inferior mesenteric arteries through the meandering artery and the marginal artery of Drummond, and between the inferior mesenteric artery and the hypogastric arteries through the hemmorrhoidal arteries ( Fig. 41-4 ). Patients with severe three-vessel disease often display increased lumbar, phrenic, and pelvic collaterals. Whereas lateral angiography can reveal the degree of stenosis, anteroposterior views are necessary to assess the collateral pathways.
Figure 41-2
Computed tomography angiogram demonstrating patency of the proximal portions of the celiac artery, superior mesenteric artery, and inferior mesenteric artery.
Figure 41-3
CT angiogram demonstrating patency of the celiac artery, superior mesenteric artery, and inferior mesenteric artery, as well as a large gastroduodenal collateral artery ( arrow ) .
Figure 41-4
Angiographic images demonstrating a large meandering collateral artery providing arterial blood supply from the inferior mesenteric artery to the superior mesenteric artery.
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If symptoms or mesenteric duplex imaging are equivocal, additional imaging should be obtained. CT angiography has very high sensitivity and specificity for mesenteric stenosis and can detect other intraabdominal pathologies. Moreover, CT angiography allows the surgeon to assess the angulation of the mesenteric artery in relation to the aorta, multifocal arterial stenosis, thrombus, and collateral pathways, as well as tortuosity, stenosis, or aneurysmal disease in the aorta or iliac arteries. All of this helps in procedural planning. When the diagnosis of chronic mesenteric ischemia is in question, such as in the case of single-vessel disease, gastric and jejunal exercise tonometry has been reported as an aid in diagnosis. Such studies are available in only a minority of centers.
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When providing consent, patients should be made aware that percutaneous mesenteric revascularization carries a risk of acute bowel ischemia because of distal embolization or arterial dissection. The operator should be prepared for an emergent open procedure if either of these problems occurs and cannot be corrected.
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Risk factor modification, such as smoking cessation, should be encouraged. Antiplatelet therapy with aspirin or clopidogrel should be initiated, and patients should begin statin therapy. Nutritional status should be assessed and improved.
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Laboratory workup should include albumin, prealbumin, vitamin B 12 , folate, coagulation parameters, a complete blood cell count, and serum creatinine. If a patient is on metformin, it should be discontinued the day of procedure and restarted 48 hours after contrast infusion if the glomerular filtration rate has not deteriorated. Preprocedural antibiotics are recommended.
Pitfalls and Danger Points
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Identification and access. Most patients with mesenteric occlusive disease, symptomatic or not, have stenosis or short-segment (2 cm) occlusions at or within the first few centimeters of the origin of the mesenteric vessels. Lesions are frequently associated with aortic atherosclerosis and atheroma, with an attendant risk of embolization during percutaneous revascularization. If occluded, the ostium of the artery may not be easily identified and gaining access to the vessel may be difficult, particularly if an occluded celiac artery precludes retrograde filling of the superior mesenteric artery ( Fig. 41-5 ).
Figure 41-5
Neither the celiac artery nor the superior mesenteric artery is visualized on anteroposterior ( A ) or lateral aortograms ( B ).
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