Imaging description

The acute angulation of the proximal celiac axis caused by a low inserting median arcuate ligament (MAL) and poststenotic dilatation gives a characteristic appearance of a “hook” and can be demonstrated using multiplanar CT angiography (Figures 77.1 and 77.2). Isolated expiratory com- pression of the celiac trunk may not be clinically significant and therefore images should be obtained at the end of maximum inspiration. Other associated findings include enlarged collateral vessels and gastroduodenal artery dilatation. Volume-rendered 3D images can assist in visualization of the severity of celiac axis compression and collateral vessels. The fibrous median arcuate ligament causing the compression can also be visualized on 3D reconstructions. Duplex ultrasound may be performed to study the severity of hemodynamic compromise. A peak systolic velocity greater than 200cm/s is considered to be diagnostic of celiac artery stenosis.

Importance

MAL is a fibrous band that connects the two cruras of the diaphragm across the aortic hiatus. It is normally located anterior to the aorta and superior to the origin of the celiac artery. In about 10–24% of normal asymptomatic individuals, it is located anterioinferiorly to the celiac axis. In such cases, MAL may cause indentation and compression of the celiac artery, compromising blood flow and causing symptoms of celiac artery compression. MAL causing celiac artery compression can also be seen in asymptomatic people and therefore caution should be taken to attribute abdominal symptoms to compression based on imaging alone and clinical correlation should be performed when incidentally noted on imaging. The decision to intervene in established cases should be based on severity of clinical and imaging findings. Presence of post-stenotic dilation, collateral vessels and gastroduodenal artery dilatation suggests hemodynamic compromise, even in asymptomatic individuals, and early intervention should be considered.