Median Arcuate Ligament Syndrome - Diagnosis

Diagnosis

Median arcuate ligament syndrome is a diagnosis of exclusion. That is, the diagnosis of MALS is generally considered only after patients have undergone an extensive evaluation of their gastrointestinal tract including upper endoscopy, colonoscopy, and evaluation for gallbladder disease and gastroesophageal reflux disease (GERD).

The diagnosis of MALS relies on a combination of clinical features and findings on medical imaging. Clinical features include those signs and symptoms mentioned above; classically, MALS involves a triad of abdominal pain after eating, weight loss, and an abdominal bruit, although the classic triad is found in only a minority of individuals that carry a MALS diagnosis.

Diagnostic imaging for MALS is divided into screening and confirmatory tests. A reasonable screening test for patients with suspected MALS is duplex ultrasonography to measure blood flow through the celiac artery. Peak systolic velocities greater than 200 cm/s are suggestive of celiac artery stenosis associated with MALS.

Further evaluation and confirmation can be obtained via angiography to investigate the anatomy of the celiac artery. Historically, conventional angiography was used, although this has been largely replaced by less invasive techniques such as computed tomography (CT) and magnetic resonance (MR) angiography. Because it provides better visualization of intraabdominal structures, CT angiography is preferred to MR angiography in this setting. The findings of focal narrowing of the proximal celiac artery with poststenotic dilatation, indentation on the superior aspect of the celiac artery, and a hook-shaped contour of the celiac artery support a diagnosis of MALS. These imaging features are exaggerated on expiration, even in normal asymptomatic individuals without the syndrome.

Proximal celiac artery stenosis with poststenotic dilatation can be seen in other conditions affecting the celiac artery. The hook-shaped contour of the celiac artery is characteristic of the anatomy in MALS and helps distinguish it from other causes of celiac artery stenosis such as atherosclerosis. This hooked contour is not entirely specific for MALS however, given that 10-24% of normal asymptomatic individuals have this anatomy.