What are the differential diagnostic considerations in a patient with suspected AMI, and how do plain abdominal radiographs help elucidate the disorder?
Flat and upright abdominal plain films should be obtained first in a patient complaining of abdominal pain unless a diagnosis of ischemia is clear.
The below table depicts differential diagnoses and associated findings on x-ray.
Radiographic Clues to Diagnosis
|Disorder||Finding on Plain Abdominal Radiographs|
|Small bowel obstruction||Dilated loops of bowel with or without air-fluid levels|
Stair-step overlapping of loops of small bowel
Termination of luminal small bowel air at transition point of obstruction
|Pancreatitis||Sentinel loop of duodenum or colon cut-off sign|
|Volvulus||Characteristic jejunal, sigmoid, or cecal dilation (sigmoid volvulus—coffee bean sign)|
|Intraabdominal sepsis (appendicitis, diverticulitis)||Air in the hepatic or portal venous system (portal venous gas)|
|Perforation||Free air under the diaphragm|
Air dissecting between bowel loops or seen retroperitoneally
|Bowel ischemia||Bowel wall thickening, loop separation, thumbprinting|
|Pneumatosis intestinalis and portal venous gas||Late signs and ominous for impending or frank infarction|
|Emphysematous cholecystitis||Air within the gallbladder wall, air-fluid level in the gallbladder (also caused by gas-forming organisms)|
Numerous imaging modalities can be employed to further elucidate a diagnosis of mesenteric ischemia, including abdominal computed tomography (CT) with contrast, Doppler of mesenteric vessels, and mesenteric angiography. Laparoscopy and enteroscopy may also be indicated in the appropriate clinical setting.
In patients with bowel infarction, plain films and abdominal CT show nonspecific abnormalities in a minority of cases. Angiography is more effective than CT in identifying mesenteric arterial occlusion or NOMI. If venous occlusive disease is suspected, a dynamic abdominal CT with contrast can be a helpful diagnostic tool.
Of note, barium for small bowel study should be avoided if a contrast CT or angiogram is being considered as barium interferes with the completion and diagnostic interpretation of the aforementioned studies.