This syndrome is very rarely diagnosed and it's not clear if this is because it actually is rare or if it often goes undiagnosed. Because it seems most common in young women in their teens and early 20s who are very thin, it is often written off as an eating disorder rather than an actual physiological disorder, despite the insistence of patients that they are not intentionally vomiting and do not want to be limiting food intake. It is said that about one third of cases are diagnosed at autopsy. Testing for MALS is usually done with imaging studies, including CAT scan, MRI, and ultrasound (a test called a mesenteric duplex ultrasound to check blood flow through the celiac artery and compression of the celiac plexus.). Treatment is surgery to stop the compression from happening. In adults, there can be the complication that the artery remains compressed even once released, probably because it's been compressed for so long.
This entry in the National Organization for Rare Disorders provides a very thorough and updated summary of the research and treatment around MALS.
There is now a laparoscopic version of the surgery that is being done at Mayo Clinic
This is a presentation of a case series of 47 patients in which surgery was done to correct the compression found in MALS. It is suggested here that MALS my be neurogenic rather than caused by vascular abnormality as is generally thought. Also, Dynamic Doppler Ultrasound was used prior to surgery (it is not clear if this was for diagnostic purposes) and the presenter says that this is an accurate test to establish the diagnosis.
Anatomy of the celiac artery
SMAS and MALS- true syndrome or fallacy? (spoiler alert- they are real)
This is a presentation that was given at Stanford medical school and is very informative.
SMAS stands for Superior Mesentery Artery Syndrome and also involves compression that leads to extreme pain. Symptoms are similar to those of MALS, mostly extreme abdominal pain, vomiting, nausea, etc. SMAS mimics a bowel obstruction and can make a person physically unable to eat so can be fatal. Similar to MALS, it is often misdiagnosed as an eating disorder. In this case it's the duodenum that is being compressed (the first part of the small intestine) that is compressed between the Superior Mesentery Artery (SMA) and the aorta. The left renal vein can also be compressed which leads to a kidney condition called Nutcracker Syndrome. SMAS is thought to be caused by dramatic weight loss resulting in loss of fat in the fat pad between the artery and duodenum, which changes the angle of the SMA to aorta. The angle is usually about 45 degrees (38 to 56), but in SMA it is under 25 degrees and can be as narrow as 6 degrees (it's usually 10 degrees or less). The distance between the SMA and the aorta is usually 10-20 mm, in SMAS it is 2-8 mm. Many people have the narrowed angle but do not have symptoms, symptoms of obstruction must be present to have SMAS.
SMA Syndrome on the show Mystery Diagnosis Part 1 Part 2 Part 3
The SMAS entry on the NORD site is very good.
This is a video of a doctor reviewing a CT scan looking for SMAS. It can be helpful to have an idea of what some of the tests are looking for and why so that as a patient you can ask the right questions to know if your scan was properly reviewed.
This same mechanism can also pinch the left renal vein which is returning blood to the heart from the kidney. This causes blood to back up in the left kidney which in turn causes renal hypertension. This causes left flank pain and blood in the urine. It is diagnosed by ultrasound, measurement of the blood flow rate, and measurement of the angle between the two arteries. Treatment focuses on gaining enough weight to cause the angle between the arteries to widen again. This helps because there is a pad of fat between the arteries that is believed to help hold the angle open and the compression seems to occur when this fat is lost. Surgery is also available.
Chronic mesenteric ischemia is a lack of blood flow to the intestines. This seems to be the same as the mechanism that causes both MALS and SMAS. This is usually worsened when a person eats. Symptoms occur because the body needs more blood for digestion than it can get from arteries because they are partially blocked. When this happens in the long run the patient can lose a lot of weight and become malnourished. Primary symptom is pain, usually after eating when trying to digest. This can be worse after eating foods that are harder to digest, such as solid vs liquid foods or high fat meals. Some foods may be more problematic than others and this seems to vary a lot between people. Treatments can be divided into 3 categories- medical management (treatments that reduce symptoms, changing risk factors that cause the disease, and preventing exacerbation of the symptoms). The second group is minimally invasive treatments (endovascular options), and lastly surgical treatments. Risk factors are generally the same as those for coronary artery disease (high blood pressure, diabetes, high cholesterol, etc) as well as chronic kidney failure. Hugh blood pressure is a major factor. Initial tests include either ultrasound to assess blood flow, or a CT angiogram which can assess blood flow in the aorta and it's branches. The most common vessels implicated include the Superior Mesenteric Artery, the Celiac Artery, and the Inferior Mesentery artery. Angiogram may also be done in which dye is injected into the abdomen via a peripherally inserted catheter so that blood flow can be seen over time.
