Benign mesenteric disease demands views other than axial CT

A comprehensive CT evaluation of the abdomen requires analysis of the mesenteric vasculature above and beyond the axial plane, according to Dr. Elliot Fishman, director of diagnostic radiology and body CT at Johns Hopkins University and Hospital.

He discussed some of the non-neoplastic disease states that benefit from advanced visualization.

"What I'm going to look at is an area that has a lot of potential for misdiagnosis. It's also an area where 3D imaging is very critical when used on a routine basis," Fishman said.

He outlined four key mesenteric abnormalities that are commonly misread, starting with superior mesenteric artery (SMA) syndrome. Clinical symptoms for this syndrome include marked weight loss or anorexia.

"Typically, the SMA angle to the aorta is around 45°. With SMA syndrome, it drops to around 10° and the SMA to aorta distance drops below 10 mm," Fishman said.

He pointed out that the sagittal plane would show the best view of SMA syndrome.

"Often it is not recognized on axial imaging," he said.

Another common miss is median arcuate ligament syndrome. Clinical symptoms can range from none at all to severe upper abdominal pain. This disease state often simulates a mass in or around the pancreatic head, according to Fishman.

"Many patients will have some compression of the celiac access. But in most cases, the patients will have no clinical symptoms. The compression is often confused with atherosclerotic disease because it looks like vessel narrowing," he said. "When you look carefully, there is no atherosclerotic change."

Fishman advised that CT readers look for a fishhook configuration to the median arcuate ligament in order to make the right diagnosis.

Another entity whose detection is hit or miss on axial CT is occlusion of the mesenteric artery.

"On axial imaging, if you get the right plane, you should be able to see occlusion or narrowing or clotting in the SMA or celiac access," Fishman said. "But you may not have the right plane. In the sagittal plane, you can see the extensive of the narrowing of the patient's SMA."

Finally, mesenteric artery aneurysm is most common in the splenic artery but can occur in the hepatic and celiac arteries as well. This type of aneurysm in the celiac artery is particularly dangerous, as it can lead to spontaneous rupture, he said.

While these disease states are all benign, properly identifying them can change patient management, Fishman said.

Fishman and colleagues evaluated how often significant mesenteric arterial abnormalities, which were identified on interactive 3D CT with volume rendering and maximum intensity projection, were also detected by routine axial images (AJR 2007:189(4):807-813). There was no clinical suspicion of mesenteric vascular disease in the 41 patients who made up the study population.

The study found that axial and 3D interpretations were equivalent in 24% of the cases. The 3D CT findings were supported by other imaging, surgery, clinical findings, or management in 49% of the cases. The mesenteric lesions identified resulted in a change in patient management in 15% (6/41) of the subjects.