MALS is a relatively rare vascular compression disorder affecting the upper abdomen. This condition, also known as Celiac Artery Compression Syndrome or Dunbar Syndrome, occurs when a band of tissue presses on a major artery. Because the symptoms often overlap with more common digestive issues, MALS is frequently overlooked or misdiagnosed, leading to prolonged patient suffering.
The Anatomy Behind the Condition
MALS arises from an unusual anatomical relationship between the diaphragm and a major abdominal blood vessel. The Median Arcuate Ligament (MAL) is a fibrous arch that connects the two muscular sections of the diaphragm, which is the primary muscle of breathing. This ligament normally sits above the Celiac Artery, the first major branch of the aorta, which supplies blood to the stomach, liver, and spleen.
In individuals with MALS, the ligament is positioned lower than typical, causing it to compress the Celiac Artery. This compression reduces blood flow through the artery, and the restriction is often worse during exhalation. The ligament can also press upon the Celiac Plexus, a dense network of nerves surrounding the artery.
The structural problem is not always present in symptomatic individuals, as some compression has been observed in healthy people without symptoms. Symptoms are thought to originate from either insufficient blood flow (ischemia) to the digestive organs or from constant irritation of the Celiac Plexus nerves. This dual vascular and neurogenic mechanism explains the varied and complex nature of the resulting pain.
Recognizing the Symptoms
The hallmark symptom of MALS is chronic, often severe, upper abdominal pain, typically localized in the area just below the ribcage. This pain is characteristically triggered or made significantly worse shortly after eating a meal. When the compressed Celiac Artery cannot meet the increased blood demand required for digestion, the resulting lack of oxygenated blood causes the pain.
The anticipation of this post-meal discomfort often leads to a condition known as sitophobia, or a fear of eating, as patients instinctively avoid food to prevent the pain. This avoidance behavior frequently results in significant, unintentional weight loss. Other common gastrointestinal symptoms include persistent nausea, vomiting, bloating, and diarrhea.
The pain in MALS may sometimes be temporarily relieved by changes in posture, such as leaning forward. Since these symptoms are not unique to MALS, patients often undergo extensive testing for conditions like ulcers, gallstones, or irritable bowel syndrome before the correct diagnosis is considered. The variable and non-specific nature of the clinical presentation means that many individuals endure a long and frustrating journey to find an explanation for their chronic pain.
Methods of Diagnosis
The diagnosis of MALS is often one of exclusion, meaning doctors must first rule out numerous other common gastrointestinal conditions causing similar abdominal pain. Once MALS is suspected, specialized imaging tests are required to visualize the dynamic compression of the Celiac Artery.
A key initial screening tool is a Duplex Doppler Ultrasound, which uses sound waves to measure the speed of blood flow through the Celiac Artery. A significant increase in the peak systolic velocity, particularly during exhalation, suggests a blockage caused by the median arcuate ligament. A velocity of 200 cm/s or greater is often used as a diagnostic benchmark for stenosis.
More definitive confirmation is achieved with a CT or MR Angiography (CTA or MRA), which creates detailed images of the blood vessels. These scans are often performed during both inspiration and expiration to capture the change in compression. The imaging often reveals a characteristic “hooked” or “J-shaped” narrowing at the origin of the Celiac Artery, where the ligament presses down on the vessel.
In some cases, a diagnostic Celiac Plexus nerve block is performed by injecting an anesthetic near the nerve network. If this injection temporarily relieves the patient’s abdominal pain, it supports the theory that the pain has a significant neurogenic component and can help predict a successful surgical outcome.
Treatment and Recovery
The primary and most effective treatment for MALS is a surgical procedure known as Median Arcuate Ligament release, or decompression. The goal of this surgery is to divide the ligament and surrounding scar tissue to permanently relieve pressure on the Celiac Artery and the Celiac Plexus nerves.
The procedure can be performed using either a traditional open surgical approach or a minimally invasive technique, such as laparoscopic or robotic surgery. The minimally invasive methods use smaller incisions and are often associated with a quicker recovery time. During the operation, an ultrasound may be used to confirm that blood flow has been successfully restored immediately after the ligament is divided.
Most patients who undergo the release surgery experience significant improvement in their abdominal pain and overall symptoms. A typical hospital stay following the procedure lasts two to three days. If the artery remains significantly narrowed after the ligament release, a second procedure to repair or reconstruct the artery may be necessary, though this is uncommon. If severe nerve-related pain persists post-surgery, a Celiac Plexus neurolysis, which involves destroying the pain-transmitting nerves, may be considered for lasting relief.