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Vascular ❯ Median Arcuate Ligament Syndrome (MALS)

ProblemSuspected median arcuate ligament syndrome (MALS)
ProtocolThe key to the study is determining what patients truly have MALS and in which cases they do not. The best phase to scan is arterial phase with deep inspiratory effort used. When expiratory phase imaging is used up to 85% could have a false positive diagnosis of MALS.

Some sites suggest a dual phase acquisition from diaphragm to iliac crest with the first phase being in deep inspiration and the second phase in expiration. It is key to look at the sagittal images to make the diagnosis. The coronal views are also helpful to look at collaterals if present to the SMA and GDA.A single acquisition in deep inspiration is enough to exclude the diagnosis of MALS.

  1. Median arcuate ligament syndrome (MALS) is one of the abdominal vascular compression syndromes diagnosed by Harjola in 1963. It is more commonly known as celiac artery compression syndrome, also known as Dunbar syndrome, named after the radiologist JD Dunbar. It typically affects young women in the ratio of 2:1 to 3:1 and age group of 20–40 years of age with a reported incidence of 2 per 100,000 patients.
  2. Median arcuate ligament syndrome or celiac artery compression syndrome is one of the abdominal vascular compression syndromes due to compression of proximal celiac artery by the median arcuate ligament. The median arcuate ligament unites diaphragmatic crura on either side at the level of aortic hiatus. The ligament has a low insertion causing compression of the celiac artery resulting in clinical symptoms of postprandial pain and weight loss. It is a rare syndrome, detected incidentally on routine Computed Tomography abdomen and pelvis studies
  3. Please note that CT studies are best evaluated in the end-inspiratory phase. Since MAL is attached to the diaphragm, movement occurs with respiration, and true compression can be evaluated in the end-inspiratory phase. Isolated compression of the celiac axis in expiration can be observed in 13%–50% of healthy individuals and can be clinically insignificant. Few of these patients would have clinical symptoms due to hemodynamic compromise. In a retrospective study, Heo et al. showed that 87% of patients with classical imaging findings of MALS incidentally detected on CT had no symptoms
  4. Dynamic CT examination may also be performed in both deep inspiration and expiration in order to evaluate the dynamic modifications in celiac artery diameter. CT imaging should include the early arterial phase acquired in deep expiration in order to increase the proximal celiac trunk compression by the median arcuate ligament, followed by the portal venous phase in deep inspiration. Sagittal and coronal images should be included for optimal visualization of the celiac artery. The proximal narrowing of the celiac trunk can be better depicted on sagittal CT reconstructions, demonstrating a focal indentation on the superior surface of the vessel with a typical “hooked appearance”, in the absence of atherosclerotic plaques or other causes of extrinsic compression.
  5. The classic clinical manifestations of MALS include chronic postprandial epigastric pain, nausea, and loss of weight due to dynamic compression of the celiac artery. However, this anatomical anomaly is asymptomatic in up to 85% of patients and may be incidentally encountered on CT examinations performed for unrelated reasons.

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