The most likely diagnosis is chronic mesenteric ischemia and the next diagnostic test should be CT angiography. Chronic mesenteric ischemia is typically a manifestation of mesenteric atherosclerosis and presents as abdominal pain beginning within 60 minutes after eating. The pain is believed to be due to diversion of small-bowel blood flow to the stomach as digestion begins. The blood flow to the small bowel, which is already compromised, then has even more limited oxygen supply, leading to ischemia and subsequent abdominal pain. This typical symptom leads to a fear of eating (sitophobia), which causes the weight loss that is seen in most patients with chronic mesenteric ischemia. Abdominal bruits are present in 50% of patients, and 50% of patients have peripheral vascular or coronary artery disease. The natural history is progression of mild pain with eating to food avoidance, weight loss, and eventually pain without eating. Upper endoscopy is typically normal, and a CT scan may show evidence of diffuse small-bowel dilation, which is suggestive of abnormal small-bowel motility. If progressive and left untreated, chronic mesenteric ischemia can rarely lead to intestinal infarction. Vascular surgical intervention is the treatment of choice. Both magnetic resonance angiography and CT angiography have high sensitivity and specificity for detecting mesenteric stenosis, although MR angiography may not be as good at detecting distal stenosis.

Doppler ultrasound is a useful screening test for chronic mesenteric ischemia. Peak systolic velocities greater than 275 cm/s in the superior mesenteric artery and greater than 200 cm/s in the celiac artery correlate with stenoses of greater than 70% in each vessel. Doppler ultrasound is often of limited use if patients are obese or there is overlying bowel gas. Ultrasonography without Doppler modality to assess blood flow will not help establish the diagnosis in this patient.

Capsule endoscopy is contraindicated in patients with small-bowel obstruction regardless of whether obstruction is due to a mechanical or functional cause (such as dysmotility due to underlying chronic ischemia, as in this patient).

Splanchnic angiography is useful if the results of noninvasive testing are equivocal to confirm the diagnosis and to plan intervention; in particular, it allows for performance of endovascular procedures at the time of diagnosis. However, owing to its invasive nature it is typically not the first diagnostic test for chronic mesenteric ischemia.