Approach Considerations
Workup for chronic mesenteric ischemia (CMI) may include the following:
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Laboratory tests
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Conventional angiography
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Computed tomography (CT) angiography (CTA)
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Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA)
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Ultrasonography
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Electrocardiography (ECG) to rule out cardiac disease
Laboratory Studies
Laboratory studies that may be considered include the following:
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Complete blood cell (CBC) count: This may demonstrate anemia, leukopenia, or lymphopenia secondary to chronic malnourishment
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Blood chemistries: These may show electrolyte abnormalities from malnutrition, vomiting, or diarrhea
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Coagulation studies: Prothrombin time (PT), activated partial thromboplastin time (aPTT), and international normalized ratio (INR)
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Liver function tests (LFTs): These may show hypoalbuminemia from malnutrition
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Urinalysis: This is done to rule out stones or infection
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Stool testing: Testing for occult blood may return positive results because of the sloughing of dead ischemic bowel; if a patient presents with steatorrhea, stool fat should be sent for examination
Angiography
Arteriography is the criterion standard for the diagnosis of chronic mesenteric ischemia (CMI) (see the image below). Typically, the arteriogram shows occlusion of two visceral branches of the aorta, with severe stenosis of the remaining visceral branch, usually the celiac trunk or the superior mesenteric artery (SMA).
Angiogram of patient with chronic mesenteric ischemia. Note diffuse occlusive disease.
CT Angiography
Computed tomography angiography (CTA) has a sensitivity of 96% and a specificity of 94% for detecting chronic mesenteric ischemia (CMI). [14] According to the American College of Radiology appropriateness criteria, it should be a first-line alternative to conventional angiography. CTA plays an especially important role in diagnosing vascular disease of the celiac trunk and the superior mesenteric artery (SMA) in CMI. [15]
In a prospective analysis comparing CTA, MRA, and duplex ultrasonography, Schaefer et al found that CTA provided the best image quality, reached the highest level of agreement and significance in correlation in stenosis grading, and offered the best diagnostic accuracy. [16]
MRI and Magnetic Resonance Angiography
Magnetic resonance angiography (MRA) appears highly promising as a diagnostic tool. [17] Until the use of fast contrast-enhanced techniques, it was limited by the acquisition time of phase-contrast or time-of-flight imaging and the development of motion artifacts. Advances in MRA technology have shortened acquisition times, so that it is now possible to obtain successive images in the arterial phase and then in the portal phase. MRA can be performed as an adjunct to any MRI examination. [18]
MRA has been evaluated for the diagnosis of chronic mesenteric ischemia (CMI) and has been shown to provide accurate imaging of the mesenteric vasculature. [19, 20] However, its ability to obtain high-resolution images of the inferior mesenteric artery (IMA) is limited; because of the IMA’s anatomic course, only about 25% of the vessel can be depicted.
In general, MRA is not considered the initial imaging method of choice in an emergency setting. [21, 22]
Ultrasonography
Mesenteric duplex ultrasonography is a useful initial screening tool for chronic mesenteric ischemia (CMI). [23, 24] It can visualize the superior mesenteric artery (SMA) in approximately 90% of cases and the celiac trunk in approximately 80%. However, transabdominal ultrasonography is rarely able to visualize the inferior mesenteric artery (IMA), because of the vessel’s anatomic location and course. Peak systolic velocity has been widely used for diagnosing stenosis, with a cutoff value of 275 cm/s for the SMA and 200 cm/s for the celiac trunk. [25]
Duplex ultrasonography is also used for assessing vascular patency after visceral bypass grafting or endovascular stenting. In a study by Baker et al, the peak systolic velocity in successfully stented SMAs remained higher than the peak systolic velocity threshold of 275 cm/s used for the diagnosis of high-grade native SMA stenosis. [26] In addition, in-stent SMA peak systolic velocity did not significantly change over duplex surveillance for patients who did not undergo reintervention.
Thus, obtaining a baseline duplex ultrasonogram early after mesenteric stenting should be considered to compare future surveillance. [26] An increase above this baseline or an in-stent SMA peak systolic velocity approaching 500 cm/s should be considered suggestive of in-stent stenosis.
It should be kept in mind that the clinical utility of duplex ultrasonography in this setting is largely dependent on operator training, bowel gas patterns, and patient body habitus. Intraperitoneal gas, respiratory movements, obesity, and previous abdominal surgical procedures may limit the sensitivity of this test.
For all practical purposes, ultrasonography should not be the initial diagnostic choice in the emergency department (ED). [21, 22]
Histologic Findings
Transected mesenteric vessels show diffuse atherosclerosis. The histologic findings from the bowel include atrophy of the tips of the villi, which leads to loss of the absorptive surface in the small bowel. The loss of the absorptive surface in conjunction with the patient’s fear of eating results in the malnourished state commonly seen in persons with chronic mesenteric ischemia.
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Angiogram of patient with chronic mesenteric ischemia. Note diffuse occlusive disease.
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Radiograph showing tortuous, dilated, meandering artery.
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Narrowing of superior mesenteric artery.
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Chronic aortic occlusion (Leriche syndrome) with acute embolic occlusion of superior mesenteric artery.
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Gas in colon wall, typical of advanced ischemia.
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Meandering artery, sign of chronic mesenteric arterial ischemia.
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Management of chronic mesenteric ischemia. Solid lines indicate accepted management plan; dashed lines indicate alternative management plan. MRA=magnetic resonance angiography; CT=computed tomography. Adapted from Gastroenterology. 2000 May; 118(5): 954-68.
