NORD gratefully acknowledges Christopher L. Skelly, MD, Elizabeth Townsend, and Grace Z. Mak, MD, University of Chicago, Department of Surgery, for the preparation of this report.
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
Since 13-50% of healthy asymptomatic patients have a form of celiac artery compression and a much smaller percentage of these patients actually report symptoms consistent with MALS,2 there is significant debate amongst doctors regarding the existence, the causes, and the management of MALS. The cause of the symptoms is thought to be due to either poor blood flow from celiac artery compression, nerve irritation from compression celiac nerve plexus, or a combination of both. Compression of the celiac artery may result in blood flow coming from another abdominal blood vessel (the superior mesenteric artery) and going to the stomach and liver when a patient eats. This is known as a “steal phenomenon” and a possible cause of abdominal pain.3-5 Another theory is that the nerves in the area of the celiac artery (the peri-aortic ganglia and celiac nerve plexus) are also thought to be overstimulated leading to spasm (vasoconstriction) of the arteries going to the stomach and small bowel and this results in symptoms. Another theory is the compression of the nerves causes interference of the brain/stomach (neuro-enteric) pain pathways resulting in hypersensitivity and pain in the stomach. Common surgical teaching maintains that chronic gastrointestinal ischemia occurs when two of the three major intestinal blood vessels have blocked blood flow; however, now many doctors believe that gastrointestinal ischemia may have a number of different causes including a neurologic component.
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.
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
Additionally, Mak et al reported incorporating psychiatric and chronic pain service in the pre-operative and post-operative evaluations given the correlation between chronic physical pain and psychological pain. Pre-operatively, all patients are evaluated by a multi-disciplinary team consisting of general and vascular surgery, psychiatry, and pain service. This team then discusses each patient, and surgery is not considered until the patient has been unanimously cleared by the entire team.4 We have found this approach to be extremely helpful to the patients.10-12
The 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
Overall, 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
Post-operative complications tend to be minor and self-limited including diarrhea, nausea, and self-limited pancreatitis. The major post-operative problem is either continued or return of the abdominal pain. An important finding is that surgery does not treat any anxiety or depression that is also present.11, 12
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
Significant controversy exists as to the true existence and the causes of this syndrome. Supporters of the syndrome attribute the symptoms to both poor blood flow (ischemia) from celiac artery compression as well as enlargement (hypertrophy) of the celiac nerve plexus and associated neuropathy. Histologic changes seen under the microscope (intimal hyperplasia, elastic fiber proliferation, and disorganization of the adventitia) in the arterial wall of the celiac artery have been described in patients with celiac artery compression as well.6 Classically, it was believed that pain of the intestine from poor blood flow (gastrointestinal ischemia) occurred when two of the three major intestinal vessels were involved; however, many physicians no longer support this notion and now believe that gastrointestinal ischemia is multifactorial in nature including a neurologic component.3, 5, 18 Opponents of MALS point to the natural finding of celiac artery compression in patients without any symptoms; additionally it is pointed out that symptoms don’t improve in all patients following surgery to treat MALS. All told, there are more factors than just compression of the celiac artery that need to be considered.11, 12, 19 Randomized controlled studies of patients diagnosed with celiac artery compression comparing non-operative management to surgery or placebo surgery to MALS release surgery would be beneficial to better delineate the effectiveness of surgery; however, there are ethical and patient perspective in the design of such trials that make them challenging. Patients seen in the clinic often request surgery as they are anxious for any possible solution due to the chronic pain. There is much opportunity to study the most effective management of these complex patients. It would also be useful to look at the patient characteristics or pre-operative evaluation that may predict success after surgical treatment as well as follow these patients for an extended period of time for long-term follow-up. Nonetheless, work needs to continue on unraveling this vexing cause of pain.
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