Challenges and pitfalls in diagnosing superior mesenteric artery syndrome: A case report

Abstract

Superior mesenteric artery syndrome is a rare condition that causes duodenal obstruction due to compression by the superior mesenteric artery and the aorta. It can be related to congenital or acquired factors that reduce the aortomesenteric angle and distance. The clinical presentation is nonspecific and often mimics other causes of upper gastrointestinal obstruction. The diagnosis requires a high index of suspicion and a correlation of clinical symptoms with radiographic findings. We report a case of a 17-year-old female patient who presented with chronic abdominal pain, vomiting, and weight loss. She was diagnosed with superior mesenteric artery syndrome based on an abdominal computed tomography scan that showed a reduced aortomesenteric angle of 30° and a reduced aortomesenteric distance of 7 mm. She was treated conservatively with anticoagulation therapy, dietary modification, and physical activity. She reported symptom improvement and weight gain after 2 weeks of treatment. This case illustrates the challenges and pitfalls in diagnosing superior mesenteric artery syndrome.

Introduction

Superior mesenteric artery (SMA) syndrome is a rare condition that causes duodenal obstruction due to compression by the SMA and the aorta. ¹ The etiology of SMA syndrome is multifactorial and can be related to congenital or acquired factors that reduce the aortomesenteric angle and distance.^1,2 The clinical presentation of SMA syndrome is nonspecific and often mimics other causes of upper gastrointestinal obstruction. ³ The diagnosis of SMA syndrome requires a high index of suspicion and correlation of clinical symptoms with radiographic findings. ³

SMA syndrome is a rare condition that can be challenging to diagnose, as it often mimics other causes of upper gastrointestinal obstruction. ¹ The incidence of SMA syndrome is estimated to be between 0.1% and 0.3%.^1,2 This case report highlights the importance of considering SMA syndrome in patients who present with postprandial abdominal pain, vomiting, early satiety, and weight loss, especially if they have risk factors such as rapid weight loss, scoliosis, spinal surgery, or trauma. ⁴ The diagnosis of SMA syndrome requires a high index of suspicion and correlation of clinical symptoms with radiographic findings. ⁴ Imaging modalities such as upper gastrointestinal series, contrast-enhanced abdominal computed tomography (CT) scan, magnetic resonance imaging (MRI), or ultrasound are essential for accurate diagnosis and timely management of SMA syndrome.^3,4

This case report presents a rare and unusual manifestation of SMA syndrome with chronic pain, this case demonstrates the importance of considering SMA syndrome in the differential diagnosis of chronic abdominal pain, especially in patients with low body mass index (BMI) and no other risk factors. It also shows the feasibility and effectiveness of non-surgical treatment in such cases.

Case presentation

Patient’s details and presentation

We report the case of a 17-year-old female who presented with chronic abdominal pain of 2 years of duration. The patient complained of severe, poorly localized, cramping abdominal pain that occurred 1 h after meals and was accompanied by vomiting. The pain was refractory to conventional medical therapy and interfered with the patient’s weight, concentration, social life, and education. The patient stated that the pain was alleviated by lying on her left side. The pain did not radiate to any other region.

History and clinical examination

Medical history was unremarkable, and there were no findings on clinical examination even at the level of abdomen examination. In addition, a gynecological examination of the pelvis showed normal findings.

Before 2 years, the patient’s BMI was 25.7 Kg/m². On admission, it was 20.1 kg/m².

Diagnostic assessment

The patient had undergone multiple diagnostic tests in the previous 2 years to establish a definitive diagnosis and rule out other possibilities. Repeated blood tests, including complete blood count and liver function tests, were normal for her age.

On admission, electrolytes and arterial blood gases were within normal ranges up to the age. The electrocardiogram showed no abnormalities. Gastroesophageal reflux disease (GERD) was suspected, but esophageal function study and upper gastrointestinal endoscopy were unremarkable. Doppler echography of the abdomen showed no abnormalities at the level of major abdominal vessels. Small bowel follow-through with gastrograffin was not performed due to a lack of resources. Abdominal computed tomography with contrast revealed a 30° angle between the abdominal aorta and the SMA, with a 7 mm obstruction of the latter after the compression point (Figure 1). Moreover, the distance between the abdominal aorta and SMA was less than 6 mm (Figure 2). Even though the patient does not have any risk factors for developing SMA syndrome, these findings confirmed the diagnosis of this syndrome.

Figure 1.

(a) and (b) CT with contrast shows the angle between the superior mesenteric artery and abdominal aorta (arrowhead). (c) 3D construction of the arteries also shows the same angle (arrowhead) in addition to discontinuity at the level of the celiac trunk (the arrow).

Figure 2.

(a) CT with contrast shows the angle between the superior mesenteric artery (SMA) and abdominal aorta. (b) A transverse section showing the distance between SMA and abdominal aorta which is 5.9 mm.

Treatment and follow-up

Non-surgical treatment was considered as the first-line treatment with administrating anti-coagulation therapy. Furthermore, the patient was advised to avoid meals that contain high levels of fat and do regular sports. After 3 months of follow-up, the patient reported no symptoms, and her BMI increased and now it is approximately 21.3 kg/m².

Discussion

SMA syndrome is a rare condition that causes duodenal obstruction due to compression by the SMA and the aorta. ⁵ The etiology of SMA syndrome is multifactorial and can be related to congenital or acquired factors that reduce the aortomesenteric angle and distance. ⁵ The clinical presentation of SMA syndrome is nonspecific and often mimics other causes of upper gastrointestinal obstruction. ⁵ The diagnosis of SMA syndrome requires a high index of suspicion and correlation of clinical symptoms with radiographic findings. ⁵

In this case report, we describe a 17-year-old female patient who presented with chronic abdominal pain, vomiting, and weight loss. She had undergone multiple diagnostic tests in the previous 2 years, but none of them revealed the cause of her symptoms. She was finally diagnosed with SMA syndrome based on an abdominal CT scan that showed a reduced aortomesenteric angle of 30°. In addition, the CT scan revealed a reduced aortomesenteric distance of 5.9 mm, which is below the diagnostic threshold of 8 mm according to the previously published studies, confirming the diagnosis of SMA syndrome. ⁵ She was treated conservatively with anticoagulation therapy, dietary modification, and physical activity. She reported symptom improvement and weight gain after 2 weeks of treatment.

This case illustrates the challenges and pitfalls in diagnosing SMA syndrome, which can lead to delayed treatment and complications. SMA syndrome is often overlooked or misdiagnosed as other conditions such as GERD, peptic ulcer disease, pancreatitis, or functional dyspepsia. ⁶ The diagnosis of SMA syndrome should be considered in patients who present with postprandial abdominal pain, vomiting, early satiety, and weight loss, especially if they have risk factors such as rapid weight loss, scoliosis, spinal surgery, or trauma. ⁷ The diagnosis can be confirmed by imaging modalities such as upper gastrointestinal series, contrast-enhanced abdominal CT scan, MRI, or ultrasound.^6,7 These imaging studies can demonstrate the characteristic findings of duodenal compression by the SMA and the aorta, such as dilatation of the proximal duodenum, narrowing of the distal duodenum, delayed gastric emptying, or positional obstruction. ⁵

The treatment of SMA syndrome depends on the severity of symptoms and the underlying cause. Conservative treatment is usually the first-line option and consists of nutritional support, anticoagulation therapy, prokinetic agents, and positional therapy. ⁸ Nutritional support aims to restore the mesenteric fat pad and increase the aortomesenteric angle and distance. It can be achieved by oral intake of high-calorie foods or enteral feeding via a nasojejunal tube or percutaneous jejunostomy tube.^7,8 Anticoagulation therapy is used to prevent thrombosis in the SMA or its branches due to stasis or turbulence. Prokinetic agents such as metoclopramide or erythromycin can enhance gastric motility and emptying.^5,8 Positional therapy involves lying on the left side or prone position to relieve the duodenal compression by gravity. Surgical treatment is reserved for patients who fail conservative treatment or have severe complications such as perforation, bleeding, or ischemia. ⁵ Surgical options include duodenojejunostomy, gastrojejunostomy, ligament of Treitz division, or vascular reconstruction.^5,7,8

The prognosis of SMA syndrome is generally good if diagnosed early and treated appropriately. However, some patients may have recurrent symptoms or complications that require long-term follow-up and management.^7,8 The mortality rate of SMA syndrome is estimated to be around 1%. ⁸

Limitations

One of the limitations of this case report was that we could not follow up on the patient who left our hospital due to personal reasons, and therefore we could not assess her long-term outcomes.

Conclusion

SMA syndrome is a rare but potentially serious condition that can cause chronic abdominal pain, vomiting, and weight loss. It requires a high index of suspicion and radiographic confirmation for diagnosis. Conservative treatment is usually effective in most cases, but surgical intervention may be needed in refractory or complicated cases. Early diagnosis and treatment can improve the quality of life and prevent morbidity and mortality in patients with SMA syndrome.