Superior mesenteric artery syndrome causing gastric outlet obstruction

Case contributed by Jason Szczepanski
Diagnosis certain

Presentation

Two-week history of abdominal bloating, pain, anorexia with a few days of nausea and vomiting. Altered bowel habits over last month. Systemically well. No significant past medical history.

Patient Data

Age: 40 years
Gender: Male

Marked distention of the stomach with some intraluminal bowel gas seen within the expected region of the duodenum. Associated elevation of the left hemidiaphragm with overlying compressive atelectasis.

Elsewhere, there is a paucity of bowel gas. Some fecal material is seen within the right colon and rectum. No large volume pneumoperitoneum or portal venous gas.

Findings are suspicious for gastric outlet obstruction.

Markedly distended stomach and duodenum, with collapse and transition point at the D3 segment where the duodenum crosses beneath the superior mesenteric artery (SMA). Appearances reflect duodenal obstruction. There is significant narrowing of the aortomesenteric angle to 19 degrees, which is suspicious of SMA syndrome.

No gastric pneumatosis or abnormal enhancement to suggest organ ischemia.

There is no superior mesenteric vessel swirling or abnormal small bowel configuration to suggest a midgut malrotation/volvulus.

Unremarkable appearance of the remainder of the small and large bowel.

Case Discussion

Superior mesenteric artery syndrome is a rare entity, with approximately 400 cases reported to have occurred worldwide.

The SMA arises from the anterior part of the abdominal aorta behind the body of the pancreas at the level of L1, 1 cm below the origin of the celiac trunk. It runs downwards, to the right forming a curve with its convexity towards the left; crossing over the third part of the duodenum, enters the root of the mesentery. When viewed laterally, the SMA is seen to run inferiorly from the anterior aspect of the aorta, surrounded by lymphatic tissues and a mesenteric pad of fat. The acute downward angle ranges from 38 to 65, which is due to the erect posture of man 1,2.

The presentation of these patients can be quite variable - from acute to chronic. The majority of patients present with a chronic history, lasting for months. They can display a large constellation of symptoms, such as weight loss, early satiety, nausea, vomiting, postprandial abdominal pain, bloating, reflux or anorexia simply due to the listed symptoms 2.

The condition can be acquired - due to severe illness such as malignancy or paraplegia, or anatomical - such as a short mesenteric root or duodenal malrotation. 

While the patient was in the Emergency Department, he had a severe episode of pain which was concerning for acute gastric perforation. He was taken to surgery where a perforation was confirmed, and he underwent a sleeve gastrectomy to repair the injury.

He had an uncomplicated recovery post-operatively.

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