Review Question - QID 106694

This patient with sudden-onset, diffuse abdominal pain, atrial fibrillation, and risk factors for vascular disease likely has acute mesenteric ischemia. For patients such as this one with suspected acute mesenteric ischemia (AMI), the best next step in management is to obtain a CT angiogram of the abdomen and pelvis to confirm the diagnosis.

Chronic mesenteric ischemia (CMI) occurs in the setting of atherosclerotic disease, with risk factors including smoking, diabetes, and dyslipidemia. Patients with CMI may present with abdominal pain exacerbated or provoked by eating and may develop food aversion, which can result in substantial weight loss and malnutrition. AMI presents upon sudden occlusion of mesenteric vessels, commonly the celiac axis or the superior mesenteric artery. Risk factors for AMI include previous CMI, arterial catheterization proximal to the takeoff of mesenteric vessels, new thrombogenic arrhythmias such as atrial fibrillation or atrial flutter. Patients present with pain out of proportion of exam. Prompt surgical intervention is key to outcomes, with revascularization being the goal. In prolonged ischemia, necrosis may develop and can present radiographically as pneumatosis intestinalis with portal venous gas (Illustration A).

Hirsch et al. discusses the natural history or peripheral arterial disease (PAD), including chronic and acute mesenteric ischemia. The greatest identified risk factors for developing PAD is notably smoking and diabetes. Postprandial abdominal pain that is reproduced or provoked by eating and is associated with weight loss should provoke consideration for chronic mesenteric ischemia. Of note, patients who develop severe abdominal pain after arterial interventions in which catheters pass the visceral aorta, or in whom have arrhythmias such as atrial fibrillation, or recent myocardial infarction, should be suspected of acute mesenteric ischemia.

Wyers discusses the diagnosis and management of acute mesenteric ischemia. The author concludes that the use of biphasic CT angiography has surpassed conventional angiography as the diagnostic method of choice because of its ability to confirm vascular occlusion, but also because of its capacity to evaluate for secondary signs of mesenteric ischemia such as pneumatosis intestinalis (Illustration A), along with other possible etiologies of the abdominal pain.

Figure A demonstrates an electrocardiogram with atrial fibrillation. Note the irregular spacing of QRS complexes, and absence of any discernible P waves.

Illustration A shows a coronal reconstruction of an abdominal CT scan with pneumatosis intestinalis and portal venous gas, suggestive of bowel ischemia and gangrene.

Incorrect Answers
Answer 1: Abdominal radiographs can be used to evaluate for pneumoperitoneum or small bowel obstruction. While certain findings associated with acute mesenteric ischemia such as portal venous gas may be visual on an abdominal radiograph, it does not visualize the abdominal vasculature and is not an appropriate test for this diagnosis.

Answer 2: Abdominal ultrasound can be used to diagnose gallbladder pathology such as cholecystitis, among others. However, it is not an appropriate test for this patient with likely acute mesenteric ischemia.

Answer 3: Colonoscopy can occasionally be utilized for patient's with acute mesenteric ischemia to visualize the bowel directly. However, it is not the most appropriate confirmatory test for this patient with likely acute mesenteric ischemia.

Answer 5: Upper endoscopy is commonly utilized to diagnose pathology of the esophagus and stomach such as peptic ulcer disease. This patient's history and presentation are more suggestive of acute mesenteric ischemia, making CT angiography the more appropriate next step.

Bullet Summary:
For patient's with suspected acute mesenteric ischemia, the most appropriate next step in management is to obtain a CT angiogram of the abdomen and pelvis.