What is the median arcuate ligament, and what is its significance?
The median arcuate ligament is an archlike fibrous band formed from fibers derived from the medial edges of the left and right diaphragmatic crura during their ascent anterosuperiorly. The median arcuate ligament may occasionally cause a stenosis of the proximal celiac artery because of extrinsic compression. The clinical significance of such a stenosis is frequently uncertain, as it is often detected incidentally on imaging in asymptomatic patients. Severe celiac stenosis and even celiac arterial occlusion are often well tolerated.
The diagnosis of median arcuate ligament syndrome (also known as celiac artery compression syndrome) can be suggested by imaging findings seen on CTA and MRA acquired during inspiration and expiration. The characteristic imaging appearance is narrowing of the nonostial proximal celiac artery during end inspiration, which is best seen in the sagittal plane. Other associated imaging findings may include poststenotic dilation, upward hooking of the celiac artery, and a prominent pancreaticoduodenal arcade. The degree of stenosis depends on the phase of the respiratory cycle, often becoming more pronounced during end expiration, because the aorta and celiac artery move superiorly during expiration.