Superior mesenteric artery syndrome (SMAS) occurs when part of the small intestine becomes squashed (compressed), meaning food and nutrients cannot pass through or be absorbed effectively.^1,2 It affects the duodenum, which is the part of the small intestine that food enters as it leaves the stomach. In SMAS, this part of the intestine becomes squashed between two arteries, the abdominal aorta and the superior mesenteric artery. This prevents the passage and absorption of food and fluids through the rest of the digestive tract and causes the accumulation of food in the stomach. This means nutrients from food, and liquids are not absorbed, leading to malnutrition and weight loss, which can be life-threatening if left untreated. The accumulation of food in the stomach causes gut symptoms and disabling pain.

Synonyms: Superior Mesenteric Artery Compression Syndrome (SMACS), Wilkie’s syndrome, aortomesenteric artery compression, cast syndrome, duodenal vascular compression, mesenteric root syndrome, Superior Mesenteric Artery Syndrome; SMAS, aortomesenteric artery duodenal compression, superior mesenteric artery compression syndrome, arterio-mesenteric duodenal compression syndrome.^1-4

Universal rare disease classifications provide a common language for recording, reporting and monitoring diseases. Please visit the Rare Disease Classifications page for more information about these internationally recognised classifications.

ORPHA: 622099 Superior mesenteric artery syndrome

ICD-11: DA52.Y Other specified vascular disorders of the duodenum

The symptoms of SMAS vary widely between individuals. Early symptoms are usually mild and include nausea, vomiting, upper abdominal pain, indigestion, constipation, and feeling full after only a small amount of food (early satiety).^{1, 3, 5} These symptoms may come and go, and in some people they can come on suddenly.

As the condition worsens, they may include debilitating pain after every meal, vomit with green or yellow coloured bile, and sudden weight loss.^{1, 3}  The discomfort associated with eating may lead people to reduce their food intake, which can lead to life -threatening malnutrition if untreated.

Please speak to your medical team to learn more about the symptoms and health implications of SMAS.

Rare diseases are often serious and progressive, exhibiting a high degree of symptom complexity, leading to significant disability. Majority of the estimated two million Australians living with a rare disease meet the Australian Government’s definition for disability (in accordance to the Australian Public Service Commission and Australian Bureau of Statistics), and many experience severe and permanent disability impacts. If you or someone you care for is experiencing disability-related impacts from a rare condition, please speak with a health or disability professional for advice. Information about relevant disability support can be found at the RARE Portal’s Disability Support Information page.

SMAS is caused by compression of the duodenum (part of the digestive tract) by two arteries (the abdominal aorta and superior mesenteric arteries). The duodenum is surrounded by a layer of fat called the mesenteric fat pad.^{1-3, 5} This acts as a protective cushion shielding the duodenum from the pressure of the body parts around it. In SMAS, this fat pad degrades (gets smaller and thinner), meaning that the arteries surrounding the duodenum (the abdominal aorta and superior mesenteric artery) can press against the duodenum and squash it.

The degradation of the mesenteric fat pad can be caused by excessive weight loss, such as due to an eating disorder, gastric bypass surgery, injury, a growth spurt without weight gain, cancers, severe burns (which can cause the body to burn fat rapidly) or conditions limiting the absorption of nutrients from food. Extended weight loss caused by SMAS can worsen the condition, as the mesenteric fat pad degrades even more, which leads to worse compression of the duodenum.

In some cases, people can also be born with very little fat around their duodenum (this is known as congenital SMAS).

Some surgeries, such as those that correct for scoliosis (misaligned spine) can alter the position of the abdominal aorta and superior mesenteric artery and also lead to SMAS.

There are no published consensus clinical diagnostic criteria diagnostic for SMAS.

Diagnosis of SMAS may be made based on a clinical examination identifying the characteristic symptoms and patient history.^1-3

As part of the diagnosis, many people may undergo imaging scans such as X-ray, computed tomography angiography (CTA) scan, or magnetic resonance imaging (MRI). These scans may help detect if there is a blockage at the duodenum, and a small angle and distance between the abdominal aorta and the superior mesenteric artery.^1-3,5

As part of the diagnosis process, doctors may also do tests to rule out other conditions that have similar symptoms (differential diagnosis), such as peptic ulcer disease, chronic idiopathic intestinal pseudo-obstruction, diabetes mellitus, gall bladder disease, irritable bowel disease, inflammation of the duodenum (duodenitis), visceral neuropathy, cyclic vomiting syndrome, inflammation of the pancreas (pancreatitis), vascular collagen condition, chronic mesenteric ischemia, median arcuate ligament syndrome (MALS) or celiac steal syndrome.

Please speak to your medical team to learn more about the available pathways for diagnosis of SMS syndrome.

Treatment is targeted at managing symptoms, ensuring nutrients are absorbed by the body, and increasing body weight to restore the fat pad surrounding the duodenum.^{1-3, 5} This usually involves a multidisciplinary care team. For individuals who develop SMA after significant weight loss, weight gain can sometimes reverse the condition.

Management strategies may include eating small meals often, supplementing meals with high energy liquids and lying in specific positions after a meal (postural therapy) which may also assist to move food thorough the duodenum.

In some cases, high energy liquids are delivered either intravenously (total parenteral nutrition) or through a feeding tube inserted through the nose to the intestine (naso-jejunal tube) to stop life-threatening malnourishment and weight loss. Surgery may be performed to direct food and liquids to bypass the crushed part of the duodenum.

Please speak to your medical team to learn more about the possible treatment or management options for your condition. Treatment will depend on an individual’s specific condition and symptoms. It is also important to stay connected to your medical team so that you can be made aware of any upcoming clinical trial opportunities.

Healthcare professionals involved in the care of individuals with SMAS may include general practitioners (GP), paediatricians, gastroenterologists, surgeons, radiologists, dieticians, pain specialists, and psychologists or psychiatrists.^{1, 2} The need for different healthcare professionals may change over a person’s lifetime and extend beyond those listed here.

Clinical care for rare diseases often involves a multidisciplinary team of medical, care and support professionals. Please note that the information provided here is as a guide and that RVA does not necessarily monitor or endorse specific clinics or health experts.

For many rare diseases, palliative care services may be relevant and useful. Palliative care services are available for people (adults, children and their families) living with a life-limiting illness. Palliative care services provide assistance, support, resources and tools to help people manage their illness and the symptoms, ease pain, and improve comfort and quality of life. Palliative care is not only for end-of-life care. It can also help at any stage of illness from diagnosis onwards, and will look different for different people. For more information about palliative care and how it can help you, please visit:

• Australian Institute of Health and Welfare: Palliative care Overview
• Australian Government Department of Health, Disability and Ageing: Palliative care
• Palliative Care Australia

We are not aware of any clinical care guidelines for superior mesenteric artery syndrome in Australia. If you know of any relevant care guidelines, please let us know via the Contribute page.

Individuals living with rare diseases may have complex medical issues and disabilities, which are not always visible. It is often useful to refer to their medical history as well as personal information such as a medical card, doctor’s letter, or if available, a rare disease passport, for relevant information.

There are specific considerations around participating in rare disease research, including clinical trials. It is important to be mindful of issues such as data privacy, research ethics, consent and differences in research regulations between Australia and other countries.

If you are interested in finding clinical trials for your condition, please visit the following websites; however, there may not be any clinical trials available:

• Australian Clinical Trials
• ClinicalTrials.gov

It is best to discuss your interest in any clinical trials with your medical team to determine suitability and eligibility.

Australian Organisation that provides support on home parenteral nutrition:
Parenteral Nutrition Down Under (PNDU)
Website: https://pndu.org/
PNDU’s mission is to support, research and inform consumers, carers and providers of parenteral nutrition for intestinal failure.

International Organisation:
SMAS Research and Awareness and Support (United States of America)
Website: https://www.smasyndrome.org/

Please note that RVA does not monitor or endorse each group/organisation’s operational governance and activities. When engaging with a group, please consider the information on the RARE Portal’s Finding Helpful Peer and Community Supports page.

SMAS varies between individuals, and each person’s experience is unique.

Personal story shared with RVA: Ebony’s Story

If you would like to share your personal story with RVA, please visit the Rare Voices Australia: Share Your Story page. RVA will consider your story for publishing on our website and inclusion on the RARE Portal.

For information on available government and social services that provide support for individuals with a rare disease, please visit the National and State Services pages.

People living with a rare disease, including families and carers, often face unique challenges such as diagnostic delays, misdiagnoses, limited treatment options, and limited access to rare disease specialists and support. These challenges may impact people’s emotional wellbeing and quality of life. Many people find it helpful to seek mental health and wellbeing support to cope with ongoing stress and uncertainty. Connecting with people who have shared experiences through a support group may also be helpful. Information about relevant mental health and wellbeing support can be found at:

• Mental Health and Wellbeing Support for Australians Living with a Rare Disease
• The National and State Services pages underneath the ‘Mental Health’ sections listed

Further information on SMAS can be found at:

• Genetic and Rare Diseases (GARD) Information Center: Superior mesenteric artery syndrome
• National Organization for Rare Disorders (NORD): Superior mesenteric artery syndrome

Orphanet: Superior mesenteric artery syndrome

This page has been developed by Rare Voices Australia (RVA)’s RARE Portal team.

If you are aware of any additional information that may benefit stakeholders with an interest in this page, or if you notice any broken links or inaccurate information, please let us know via the Contribute page.