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Median Arcuate Ligament Syndrome (MALS)

Median Arcuate Ligament Syndrome, or MALS, is an underdiagnosed condition where a ligament (a band of tissue) in your body presses down on a blood vessel called the celiac artery and the celiac plexus, which can cause pain and other symptoms. The ligament is part of the diaphragm, the muscle that helps you breathe. Some people are born with their blood vessels or ligaments in slightly different positions, which can make this problem more likely depending on the exact location of the structures. Exhaling often makes the pressure worse.

  • For Patients
  • For Physicians
For Patients

What Is It?

Median Arcuate Ligament Syndrome, or MALS, is an underdiagnosed condition where a ligament (a band of tissue) in your body presses down on a blood vessel called the celiac artery and the celiac plexus, which can cause pain and other symptoms. The ligament is part of the diaphragm, the muscle that helps you breathe. Some people are born with their blood vessels or ligaments in slightly different positions, which can make this problem more likely depending on the exact location of the structures. Exhaling often makes the pressure worse.1

Although many people may have a compression of this artery, most don’t have any symptoms. Only a small portion of patients develop any problems or symptoms.2

MALS anatomy
A. Normal anatomy near the diaphragm. B. Anatomy of a person with MALS while breathing in. The ligament doesn’t usually squeeze the celiac artery too much in this position. C. Anatomy of a person with MALS while breathing out. The ligament squeezes the celiac artery a lot in this position.9 CC BY

Who Gets It and What Are the Symptoms?

MALS usually affects women between the ages of 20 and 40, but it can happen to others too. Symptoms may include:1-4

  • Pain in the upper stomach after eating
  • Nausea (feeling like you’re going to throw up)
  • Vomiting
  • Bloating
  • Upper stomach pain after exercising
  • Avoiding food because of the pain
  • Unintentional weight loss
  • Bowel dysmotility

These symptoms are likely caused by nerves around the artery/celiac plexus getting irritated or by not having enough blood reaching different areas of the body due to the compression.

How Is It Diagnosed?

Doctors use special scans like ultrasound and CT angiography to look at the blood vessels and see if they are being compressed.2 Before testing for MALS, doctors usually check for more common causes of stomach pain and other symptoms.

To be diagnosed with MALS, doctors look for:5

  • Imaging that shows compression of the celiac artery by the MAL
  • Pain when pressure is applied to the celiac plexus
  • Pain that goes away completely for a short time after a nerve block (a procedure that numbs the area), including pain felt after eating and food intolerance

How Is It Treated?

If a nerve block helps with pain, it usually means the pain is coming from the nerves of the celiac plexus. This can also mean that surgery might help. The goal of surgery is to stop the pain by removing the ligament that’s pressing on the artery.6

In the past, doctors had to open the stomach for surgery (laparotomy), but now many patients have less invasive surgery using small tools and cameras (laparoscopic or robotic surgery). During surgery, the ligament and nearby nerves are removed to relieve the pressure.7

SAFIRE’s Role

The reason MALS occurs is not fully understood, and standardized diagnostic criteria are lacking.1,8 Responses to treatment can vary, which emphasizes the need for further research. SAFIRE is committed to advancing education, supporting clinical research, and enhancing patient access to multidisciplinary care.

Patients, healthcare professionals, and researchers interested in contributing to these efforts are encouraged to support SAFIRE’s mission by making a contribution through our donation platform.

References

  1. Goodall R, Langridge B, Onida S, Ellis M, Lane T, Davies AH. Median arcuate ligament syndrome. J Vasc Surg. 2020;71(6):2170–2176.
  2. Horton KM, Talamini MA, Fishman EK. Median arcuate ligament syndrome: evaluation with CT angiography. Radiographics. 2005;25(5):1177–1182.
  3. Giakoustidis A, Moschonas S, Christodoulidis G, et al. Median arcuate ligament syndrome often poses a diagnostic challenge: A literature review with a scope of our own experience. World J Gastrointest Surg. 2023;15(6):1048–1055.
  4. Iqbal S, Chaudhary M. Median arcuate ligament syndrome (Dunbar syndrome). Cardiovasc Diagn Ther. 2021;11(5):1172–1176.
  5. Barbon DA, Hsu R, Noga J, Lazzara B, Miller T, Stainken BF. Clinical Response to Celiac Plexus Block Confirms the Neurogenic Etiology of Median Arcuate Ligament Syndrome. J Vasc Interv Radiol. 2021;32(7):1081–1087.
  6. Upshaw W, Richey J, Ravi G, et al. Overview of Median Arcuate Ligament Syndrome: A Narrative Review. Cureus. 2023;15(10):e46675.
  7. Sun Z, Zhang D, Xu G, Zhang N. Laparoscopic treatment of median arcuate ligament syndrome. Intractable Rare Dis Res. 2019;8(2):108–112.
  8. Björck M, Koelemay M, Acosta S, et al. Editor’s Choice – Management of the Diseases of Mesenteric Arteries and Veins: Clinical Practice Guidelines of the European Society of Vascular Surgery (ESVS). Eur J Vasc Endovasc Surg. 2017;53(4):460–510.
  9. Liu Y, Zheng H, Wang X, Wang Z, Zhu Q, Wen C, Tong Y. Ultrasound characteristics of abdominal vascular compression syndromes. Front Cardiovasc Med. 2023 Dec 18;10:1282597. doi: 10.3389/fcvm.2023.1282597. PMID: 38173818; PMCID: PMC10764025.
For Physicians

Background

Median arcuate ligament syndrome (MALS) is an underdiagnosed midline compression disorder characterized by extrinsic compression of the celiac artery and celiac plexus by the median arcuate ligament (MAL). The MAL is the confluence of the muscle fibers from the diaphragmatic crura forming the aortic hiatus. Anatomical variations including low insertion of the MAL or high origin of the celiac artery can predispose a patient to median arcuate ligament syndrome. The degree of compression often varies with respiration, typically worsening during expiration.1

While the true prevalence of MALS remains uncertain, studies suggest that 10% to 24% of individuals may have some degree of celiac artery indentation by the MAL. However, the majority remain asymptomatic, with only a minority developing clinically significant symptoms consistent with MALS.2

Clinical Presentation

MALS predominantly affects women and often presents between the ages of 20 and 40. Symptomatology includes:1-4

  • Postprandial epigastric pain
  • Nausea
  • Vomiting
  • Bloating
  • Epigastric pain after exercise
  • Food aversion due to pain
  • Unintentional weight loss

These symptoms are believed to result from neurogenic inflammation of the celiac plexus. An older theory that is falling out of favor includes mesenteric ischemia secondary to extrinsic compression. This is felt to be in question as there is a very rich blood supply to the upper abdomen and in elderly patients with chronic ischemia to the gut, it requires 2 of the 3 main mesenteric vessels to be completely occluded before patients develop symptoms.

MALS anatomy
(A) Normal median arcuate ligament (MAL) position; (B) lower MAL position: no significant celiac artery compression during inspiration; (C) lower MAL position: celiac artery compressed by the MAL during expiration.9 CC BY

Diagnostic Criteria

Diagnostic modalities include duplex ultrasonography with respiratory maneuvers, computed tomography angiography (CTA), and uncommonly, conventional angiography.2  Patients undergoing evaluation for MALS should first undergo full gastroenterology workup for common causes of epigastric pain.

While ultrasound of the celiac artery with inspiration and expiration used to be the gold standard for diagnosis, CTA is more helpful in not missing patients who have neurologic compression without direct changes in the celiac artery.

Inclusion diagnostic criteria for MALS consist of imaging confirming extension of the median arcuate ligament onto the main trunk of the celiac artery, pain when pressure is applied to the celiac plexus, and celiac plexus block achieving transient but complete relief of pain, including relief of postprandial epigastric pain and food intolerance.5

Treatment

CT guided celiac plexus block achieving relief of postprandial epigastric pain indicates neurogenic pain arising from the celiac plexus and serves as a prognosticator of surgical outcomes.  The goal of operative intervention in MALS patients is for relief of disabling epigastric pain.6  Historically, laparotomy for median arcuate ligament release was standard; however, minimally invasive approaches (laparoscopic or robotic assisted) have become more commonplace due to reduced morbidity and improved recovery times. Operative correction of MALS include division or resection of the median arcuate ligament away from the celiac artery, and resection of the celiac plexus surrounding the celiac artery and its branches.7

Clinicians seeking expert consultation and management resources can refer to SAFIRE’s network of experienced providers.

SAFIRE’s Role

MALS pathophysiology is not fully understood, and standardized diagnostic criteria are lacking.1,8 Therapeutic responses vary, highlighting the need for further research. SAFIRE is committed to advancing education, supporting clinical and translational research, and enhancing patient access to multidisciplinary care.

Patients, healthcare professionals, and researchers interested in contributing to these efforts are encouraged to support SAFIRE’s mission by making a contribution through our donation platform.

References

  1. Goodall R, Langridge B, Onida S, Ellis M, Lane T, Davies AH. Median arcuate ligament syndrome. J Vasc Surg. 2020;71(6):2170–2176.
  2. Horton KM, Talamini MA, Fishman EK. Median arcuate ligament syndrome: evaluation with CT angiography. Radiographics. 2005;25(5):1177–1182.
  3. Iqbal S, Chaudhary M. Median arcuate ligament syndrome (Dunbar syndrome). Cardiovasc Diagn Ther. 2021;11(5):1172–1176.
  4. Giakoustidis A, Moschonas S, Christodoulidis G, et al. Median arcuate ligament syndrome often poses a diagnostic challenge: A literature review with a scope of our own experience. World J Gastrointest Surg. 2023;15(6):1048–1055.
  5. Barbon DA, Hsu R, Noga J, Lazzara B, Miller T, Stainken BF. Clinical Response to Celiac Plexus Block Confirms the Neurogenic Etiology of Median Arcuate Ligament Syndrome. J Vasc Interv Radiol. 2021;32(7):1081–1087.
  6. Upshaw W, Richey J, Ravi G, et al. Overview of Median Arcuate Ligament Syndrome: A Narrative Review. Cureus. 2023;15(10):e46675.
  7. Sun Z, Zhang D, Xu G, Zhang N. Laparoscopic treatment of median arcuate ligament syndrome. Intractable Rare Dis Res. 2019;8(2):108–112.
  8. Björck M, Koelemay M, Acosta S, et al. Editor’s Choice – Management of the Diseases of Mesenteric Arteries and Veins: Clinical Practice Guidelines of the European Society of Vascular Surgery (ESVS). Eur J Vasc Endovasc Surg. 2017;53(4):460–510.
  9. Liu Y, Zheng H, Wang X, Wang Z, Zhu Q, Wen C, Tong Y. Ultrasound characteristics of abdominal vascular compression syndromes. Front Cardiovasc Med. 2023 Dec 18;10:1282597. doi: 10.3389/fcvm.2023.1282597. PMID: 38173818; PMCID: PMC10764025.

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