Median arcuate ligament syndrome (MALS) is a rare disorder characterized by chronic, recurrent abdominal pain related to compression of the celiac artery (which supplies blood to the upper abdominal organs) by the median arcuate ligament (a muscular fibrous band of the diaphragm). It usually presents with symptoms of abdominal pain, weight loss, and an abdominal bruit (abnormal sound of a blood vessel when blocked or narrowed).

The cause is not fully understood; however, it is suspected that there could be a combination of vascular (blood supply) and neurogenic (neurological) components involved. Diagnosis is usually confirmed with imaging such as CT angiography, MRI, ultrasound, and arteriography. Surgery is currently the only treatment option and involves releasing the ligament.

Celiac trunk (also, celiac artery) is a major branch of the abdominal aorta; gives rise to the left gastric artery, the splenic artery, and the common hepatic artery that forms the hepatic artery to the liver, the right gastric artery to the stomach, and the cystic artery to the gall bladder

common hepatic artery is a branch of the celiac trunk that forms the hepatic artery, the right gastric artery, and the cystic artery.

left gastric artery is a branch of the celiac trunk; supplies blood to the stomach

splenic artery is branch of the celiac trunk; supplies blood to the spleen

The thoracic aorta begins at the level of vertebra T5 and continues through to the diaphragm at the level of T12, initially traveling within the mediastinum to the left of the vertebral column. As it passes through the thoracic region, the thoracic aorta gives rise to several branches, which are collectively referred to as visceral branches and parietal branches (Figure 20.28). Those branches that supply blood primarily to visceral organs are known as the visceral branches and include the bronchial arteries, pericardial arteries, esophageal arteries, and the mediastinal arteries, each named after the tissues it supplies. Each bronchial artery (typically two on the left and one on the right) supplies systemic blood to the lungs and visceral pleura, in addition to the blood pumped to the lungs for oxygenation via the pulmonary circuit. The bronchial arteries follow the same path as the respiratory branches, beginning with the bronchi and ending with the bronchioles. There is considerable, but not total, intermingling of the systemic and pulmonary blood at anastomoses in the smaller branches of the lungs. This may sound incongruous—that is, the mixing of systemic arterial blood high in oxygen with the pulmonary arterial blood lower in oxygen—but the systemic vessels also deliver nutrients to the lung tissue just as they do elsewhere in the body. The mixed blood drains into typical pulmonary veins, whereas the bronchial artery branches remain separate and drain into bronchial veins described later. Each pericardial artery supplies blood to the pericardium, the esophageal artery provides blood to the esophagus, and the mediastinal artery provides blood to the mediastinum. The remaining thoracic aorta branches are collectively referred to as parietal branches or somatic branches, and include the intercostal and superior phrenic arteries. Each intercostal artery provides blood to the muscles of the thoracic cavity and vertebral column. The superior phrenic artery provides blood to the superior surface of the diaphragm. Table 20.7 lists the arteries of the thoracic region.

Figure 20.28 Arteries of the Thoracic and Abdominal Regions The thoracic aorta gives rise to the arteries of the visceral and parietal branches.

Arteries of the Thoracic Region

Table 20.7

Abdominal Aorta and Major Branches

After crossing through the diaphragm at the aortic hiatus, the thoracic aorta is called the abdominal aorta (see Figure 20.28). This vessel remains to the left of the vertebral column and is embedded in adipose tissue behind the peritoneal cavity. It formally ends at approximately the level of vertebra L4, where it bifurcates to form the common iliac arteries. Before this division, the abdominal aorta gives rise to several important branches. A single celiac trunk (artery) emerges and divides into the left gastric artery to supply blood to the stomach and esophagus, the splenic artery to supply blood to the spleen, and the common hepatic artery, which in turn gives rise to the hepatic artery proper to supply blood to the liver, the right gastric artery to supply blood to the stomach, the cystic artery to supply blood to the gall bladder, and several branches, one to supply blood to the duodenum and another to supply blood to the pancreas. Two additional single vessels arise from the abdominal aorta. These are the superior and inferior mesenteric arteries. The superior mesenteric artery arises approximately 2.5 cm after the celiac trunk and branches into several major vessels that supply blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine. The inferior mesenteric artery supplies blood to the distal segment of the large intestine, including the rectum. It arises approximately 5 cm superior to the common iliac arteries.

In addition to these single branches, the abdominal aorta gives rise to several significant paired arteries along the way. These include the inferior phrenic arteries, the adrenal arteries, the renal arteries, the gonadal arteries, and the lumbar arteries. Each inferior phrenic artery is a counterpart of a superior phrenic artery and supplies blood to the inferior surface of the diaphragm. The adrenal artery supplies blood to the adrenal (suprarenal) glands and arises near the superior mesenteric artery. Each renal artery branches approximately 2.5 cm inferior to the superior mesenteric arteries and supplies a kidney. The right renal artery is longer than the left since the aorta lies to the left of the vertebral column and the vessel must travel a greater distance to reach its target. Renal arteries branch repeatedly to supply blood to the kidneys. Each gonadal artery supplies blood to the gonads, or reproductive organs, and is also described as either an ovarian artery or a testicular artery (internal spermatic), depending upon the sex of the individual. An ovarian artery supplies blood to an ovary, uterine (Fallopian) tube, and the uterus, and is located within the suspensory ligament of the uterus. It is considerably shorter than a testicular artery, which ultimately travels outside the body cavity to the testes, forming one component of the spermatic cord. The gonadal arteries arise inferior to the renal arteries and are generally retroperitoneal. The ovarian artery continues to the uterus where it forms an anastomosis with the uterine artery that supplies blood to the uterus. Both the uterine arteries and vaginal arteries, which distribute blood to the vagina, are branches of the internal iliac artery. The four paired lumbar arteries are the counterparts of the intercostal arteries and supply blood to the lumbar region, the abdominal wall, and the spinal cord. In some instances, a fifth pair of lumbar arteries emerges from the median sacral artery.

The aorta divides at approximately the level of vertebra L4 into a left and a right common iliac artery but continues as a small vessel, the median sacral artery, into the sacrum. The common iliac arteries provide blood to the pelvic region and ultimately to the lower limbs. They split into external and internal iliac arteries approximately at the level of the lumbar-sacral articulation. Each internal iliac artery sends branches to the urinary bladder, the walls of the pelvis, the external genitalia, and the medial portion of the femoral region. In females, they also provide blood to the uterus and vagina. The much larger external iliac artery supplies blood to each of the lower limbs. Figure 20.29 shows the distribution of the major branches of the aorta into the thoracic and abdominal regions. Figure 20.30 shows the distribution of the major branches of the common iliac arteries. Table 20.8 summarizes the major branches of the abdominal aorta.

Figure 20.29 Major Branches of the Aorta The flow chart summarizes the distribution of the major branches of the aorta into the thoracic and abdominal regions.

Figure 20.30 Major Branches of the Iliac Arteries The flow chart summarizes the distribution of the major branches of the common iliac arteries into the pelvis and lower limbs. The left side follows a similar pattern to the right.

Vessels of the Abdominal Aorta

Table 20.8

The cause of median arcuate ligament syndrome (MALS) is disputed. While it was initially thought to be caused by a restriction of blood supply secondary to compression of the celiac artery (supplies blood to the upper abdominal organs) by the median arcuate ligament (a muscular fibrous band of the diaphragm), other factors have been proposed. It has been suggested that nerve dysfunction might additionally be involved, which could explain some of the associated symptoms such as pain and delayed gastric emptying.

Classically, individuals with median arcuate ligament syndrome (MALS) present with a triad of abdominal pain after eating, weight loss (usually >20 pounds), and abdominal bruit (abnormal sound of a blood vessel when blocked or narrowed).

One review found that abdominal pain is the most common symptom, found to be present in approximately 80% of individuals, while weight loss was found in approximately 48% and abdominal bruit was appreciated in approximately 35%.

Other symptoms include: nausea, diarrhea, vomiting, and delayed gastric emptying.

A diagnosis of median arcuate ligament syndrome (MALS) might be suspected in middle aged (40-60) female patients with a triad of symptoms including abdominal pain after eating, weight loss, and abdominal bruit (abnormal sound of a blood vessel when blocked or narrowed). Abdominal imaging is used to confirm the diagnosis and rule out other similarly presenting disorders. Imaging methodologies might include: CT angiography, MRI, ultrasound, and arteriography.

Surgery is currently the only treatment option for median arcuate ligament syndrome (MALS). Surgery typically involves decompression of the celiac artery by dividing the fibers of the median arcuate ligament and celiac plexus (network of nerves in the abdomen). Surgical decompression might additionally be combined with stent placement, angioplasty, or vascular reconstruction of the celiac artery.

The prognosis for median arcuate ligament syndrome (MALS) varies. While long-term relief of symptoms has been described, many individuals unfortunately do not experience clinical benefits from surgery. In a large study of 51 individuals treated for MALS, the following factors were found to be associated with a favorable outcome after surgery:

• Pain after eating (81% cured)
• Age between 40 and 60 (77% cured)
• Weight loss of 20 pounds or more (67% cured)

Less success was associated with the following factors:

• Atypical pain patterns with periods of remission (43% cured)
• Age greater than 60 (40% cured)
• A history of psychiatric disorder or alcohol abuse (40% cured)
• Weight loss less than 20 pounds (53% cured)