الفهرس 
Anatomy And EmbryologyOnly 14 pages are availabe for public view
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Abstract
Mesenteric ischemia occurs when perfusion of the visceral organs fails to meet normal metabolic requirements. This disorder is categorized as either acute or chronic, based on the duration of symptoms. The most common cause of AMI is embolization to the SMA. Arterial thrombosis constitutes the next most common cause of AMI and occurs in 20% to 35% of cases. Preexisting atherosclerotic plaque affecting all visceral vessels is the most common finding. Impaired intestinal perfusion in the absence of thromboembolic occlusion is termed nonocclusive mesenteric ischemia (NOMI). Symptomatic patients are frequently found to have extensive atherosclerosis, with involvement of all three visceral arteries. MVT constitutes 5% to 15% of all cases of mesenteric ischemia. Involvement is usually limited to the superior mesenteric vein but can also involve the inferior mesenteric vein and portal vein.The most common symptom of AMI associated with arterial thromboembolic disease is the sudden onset of abdominal pain. Lack of collateral flow to the visceral organs leads to a more dramatic presentation in AMI, with severe, rapid clinical deterioration. Nausea, vomiting, diarrhea, and abdominal distention can also occur.Postprandial abdominal pain and progressive weight loss are the most common symptoms in patients with CMI. Pain is often described as dull and crampy and located in the midepigastric region (Cronenwett and Johnston, 2010).
Duplex ultrasonography is a useful tool for the early, noninvasive diagnosis of visceral ischemic syndromes. Color Doppler scanning can be used to assess the flow velocities and resistance index in the splanchnic arteries and their arterial beds. Computed tomography (CT) is an accurate, noninvasive imaging modality for diagnosing mesenteric ischemia. Advantages over conventional angiography include the relative ease and speed of performance. Common radiographic findings in the bowel wall related to AMI include increased thickening, dilatation, and attenuation, which can be easily detected using CT. Disadvantages of CT include the risk of contrast nephropathy and hypersensitivity reactions to iodinated contrast agents. Inaccurate timing of contrast infusion during the arterial phase may provide indeterminate images and delay diagnosis. Magnetic resonance angiography (MRA) is useful for diagnosing mesenteric occlusive disease. Because MRA takes significantly longer to perform than CTA, its role in evaluating patients with AMI is limited. Conventional angiography remains the “gold standard” in the diagnosis of mesenteric ischemia. Anteroposterior and lateral views of the visceral aorta, as well as selective catheterization of the celiac trunk, SMA, and IMA, provide the most accurate and specific localization of stenotic and occlusive lesions (Cronenwett and Johnston, 2010).
Therapeutic alternatives such as balloon angioplasty, stenting, and thrombolysis and percutaneous thrombus extraction can all be used to restore luminal visceral blood flow. Medical treatment alone is not effective in these patients. Preventive risk factor modification helps control the progression of atherosclerosis in the mesenteric circulation. Patients with known risks for inheritable hypercoagulable disorders should undergo screening and should be treated with systemic anticoagulation. Advances in endovascular techniques have greatly expanded the role of percutaneous interventions for patients with mesenteric ischemia. However, endovascular management remains largely limited to patients with CMI. Because patients with AMI frequently require intestinal resection, laparotomy with open revascularization is the preferred method of treatment. In those with short-segment stenoses, cardiac and pulmonary co-morbidities, prior abdominal surgery, coagulopathy, or malnutrition, endovascular therapy is often favored. More complex lesions and complete arterial occlusions traditionally favor open revascularization (Sreenarasimhaiah, 2005).
Laparotomy with visceral revascularization can be used to treat patients with both AMI and CMI. Several techniques for the restoration of intestinal perfusion are available to the vascular surgeon (Park et al., 2002).