Arcuate Artery

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The arcuate artery of the foot (metatarsal artery) arises from dorsalis pedis slightly anterior to the lateral tarsal artery, specifically over the naviculocuneiform joint; it passes lateralward, over the bases of the lateral four metatarsal bones, beneath the tendons of the extensor digitorum brevis, its direction being influenced by its point of origin; and it terminates in the lateral tarsal artery. It communicates with the plantar arteries through the perforating arteries of the foot.

The median arcuate ligament syndrome (MALS) is a cause of chronic abdominal pain affecting both children and adults alike. Chronic abdominal pain is a very common condition that can have significant negative, long-term psychosocial consequences, including increased risk for anxiety, school and work absences, poor functional capacity, and a poor quality of life. While the exact cause of the pain is unknown, compression of the celiac artery and/or the celiac plexus nerves by the diaphragm can result in pain that is worsened with eating or sometimes with exercise. Other symptoms include nausea and weight loss. In some patients the symptoms can be devastating and can lead to erroneous diagnoses of an eating disorder, psychiatric conditions, or functional abdominal pain (e.g. irritable bowel syndrome, abdominal migraine). The diagnosis is made based on a combination of the clinical symptoms and radiology imaging. There is a surgical procedure that can be performed that is effective in approximately 60-80% of patients.

Compression of the celiac artery by the median arcuate ligament is a poorly understood vascular compression syndrome involving the celiac artery and celiac nerve plexus that results in upper abdominal pain (frequently made worse with eating), weight loss, nausea and vomiting. Sometimes a doctor may hear a soft whooshing sound with a stethoscope (bruit) over the upper abdomen that may mean there is a vascular blockage. Some patients who are athletes may experience recurrent upper abdominal pain that is brought on by moderate to intense cardiovascular work outs. Additional symptoms associated with the diagnosis, but frequently indicative of other medical problems include palpitations (hearing or feeling your own heartbeat), chest pain, diarrhea, constipation, and difficulty sleeping.

The median arcuate ligament is formed by the merging of the right and left attachments of the diaphragm as they cross over the aorta as it enters the abdominal cavity from the chest. The relationship of the ligament to the celiac artery origin determines compression: when the celiac artery comes off the aorta above the diaphragm, this can result in compression; when the celiac artery branches off the aorta below the diaphragm, there is no compression. In a study of 75 autopsies, the median arcuate ligament crossed the celiac artery origin entirely (33%) or partially (48%) in a majority of individuals, resulting in significant celiac artery compression.1

The characteristic MALS patient is more likely to be young adult female, which is consistent with demographic characteristics of other chronic abdominal pain (CAP) patients. However, given the wide distribution of celiac artery compression, the syndrome affects both young and old as well as women and men.

The combination of upper abdominal pain and the finding of celiac artery compression on radiologic studies suggests the diagnosis of the MALS. The challenge with celiac artery compression is that a significant proportion of the population (13-50%) exhibit radiographic features of celiac artery compression, but do not demonstrate any symptoms. This has led to significant controversy regarding the existence and management of this syndrome.

Because there are many patients with celiac artery compression and no symptoms, and because there are many causes for abdominal pain, it is important that patients are evaluated for all possible common causes of abdominal pain before being diagnosed with MALS. (Table 1)

There has been very little published with specific protocols for diagnosis of MALS. Mak, et al reported the use of a specific diagnostic protocol. Complete medical evaluation should include blood work (complete blood count, chemistry panel, liver function tests, amylase, lipase, inflammation markers (erythrocyte sedimentation rate, C-reactive protein), pre-albumin, thyroid function tests), upper gastrointestinal imaging studies, small bowel follow-through, abdominal ultrasound, upper endoscopy with biopsy, and evaluation for inflammatory bowel disease and celiac disease. Patients are then screened with mesenteric duplex ultrasound. Positive findings demonstrate elevated blood flow velocities (PSV=peak systolic velocity) in the celiac artery greater than 200 cm/sec and an end diastolic velocity (EDV) greater than 55 cm/sec. Further demonstration of a decrease or even normalization of the velocities with deep inspiration is suggestive of celiac artery compression.4 Patients then undergo CT (computerized tomography) scan, MRA (magnetic resonance angiogram) or sometimes an angiogram to confirm the change in the shape of the celiac artery in both inspiratory and expiratory phases.4

Once other common causes of pain have been excluded and celiac artery compression is confirmed, it is crucial that patients are evaluated for proper patient selection for surgical intervention. Patient characteristics reported to be predictive of successful outcomes following surgery include consistent abdominal pain after eating, patients between the ages of 40-60 years, and weight loss of 20 pounds or greater. Surgery tends to not help in patients in which the pain is atypical, there are periods of remission, in patients over the age of 60 years, in patients with a history of alcohol abuse, and weight loss of less than 20 pounds.4, 6-9

TreatmentThe standard treatment of celiac artery compression syndrome is surgical release of the celiac artery from compression with simultaneous removal of the nerves that are being compressed as well. The different techniques for the surgical release of celiac artery compression consist of open, laparoscopic, and robotic procedures (all of which have been shown to be safe and effective) without any evidence to support one approach being better than the other. The general principles of the operation are: division of the median arcuate ligament including overlying lymphatics and soft tissue to relieve the compression of the celiac artery with or without division of the celiac nerve plexus. Some surgeons use ultrasound to verify adequate release while other surgeons determine adequate release by conformational change of the celiac artery. While there is debate regarding performance of celiac artery revascularization procedures concomitantly with the release or at a later date if symptoms recur, there is no reason to perform endovascular stenting of the celiac artery pre-operatively as these stents generally fail due to external compression from the median arcuate ligament.3, 5, 13, 14 One novel approach was described by van Petersen in which retroperitoneal endoscopic lysis of the median arcuate ligament was performed with similar safety and success rates.15

Surgical OutcomesOverall, reviews have found generally good outcomes following surgical treatment of MALS with the majority of studies showing improved post-operative abdominal pain. Average success rate of being symptom-free following surgical intervention is reported to be 60-80%.16, 17 However, optimal surgical outcomes are not universal. One of the few larger published series by Mak et al consists of 46 pediatric cases treated by laparoscopic release of the median arcuate ligament. The success rate was reported to be 83% with improved abdominal pain and quality of life. Post-operatively, a total of six patients required additional procedures due to persistent abdominal pain and nausea (two celiac plexus nerve blocks, two angiographies with angioplasties, one open aorto-celiac bypass, and one local block at previous umbilical port incision). Of these six patients, four still reported no improvement in abdominal pain. One of the limitations of this study was the poor compliance in completing the post-operative quality of life surveys. This improved later in the study but led to poor long-term follow-up data for the initial patients.4 The second large published series by van Petersen consisted of 46 patients who underwent retroperitoneal endoscopic release of the median arcuate ligament. They reported a success rate of 89% with 30 patients reporting no symptoms at follow-up and 11 patients reporting clear improvement of symptoms.15

For those patients with recurrent or persistent abdominal pain, they are re-evaluated for possible re-narrowing of the celiac artery either due to formation of scar tissue in the artery wall (intravascular web) or the natural conformation of the celiac artery. These patients may require additional procedures typically with a balloon angioplasty. Additionally, there are some patients with recurrent or persistent abdominal that will now have normal blood flow. This suggests that they have chronic functional abdominal pain. Mak et al published a protocol for those patients with persistent symptoms. Repeat duplex ultrasound is first performed. Patients with significantly elevated velocities as well as continued respiratory variation then undergo angiography with possible angioplasty. In those patients with normalized celiac artery velocities, repeat CT angiogram is performed to evaluate for intra-abdominal pathology following surgery. If the CT is normal, patients are offered celiac plexus nerve block by anesthesia and are counseled that they may have functional abdominal pain.4

3. Sultan S, Hynes N, Elsafty N and Tawfick W. Eight years experience in the management of median arcuate ligament syndrome by decompression, celiac ganglion sympathectomy, and selective revascularization. Vasc Endovascular Surg. 2013; 47: 614-9. 59ce067264

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