Superior Mesenteric Artery Syndrome (SMAS)

SMAS, delayed gastric emptying, and gastroparesis

SMAS can do more than cause vomiting from a narrow duodenal passage. The obstruction can back up the stomach and proximal duodenum, creating chronic distention and delayed gastric emptying. Patients may therefore have symptoms and even gastric-emptying studies that resemble gastroparesis.

Because formal gastroparesis is defined as delayed gastric emptying without mechanical obstruction, clinicians should interpret a delayed gastric-emptying study carefully when active SMAS is still present. In some patients, the delayed emptying is at least partly secondary to the duodenal obstruction.

When SMAS surgery successfully relieves the obstruction, gastric emptying and feeding tolerance can improve. Published radionuclide gastric-emptying studies document postoperative improvement in some patients. Other patients continue to have delayed emptying because chronic gastric/duodenal atony or a separate motility disorder remains.

For that reason, VCA considers preoperative and postoperative gastric-emptying results, oral intake, tube-feeding requirements, and long-term feeding tolerance important outcome measures rather than treating SMAS surgery as simply 'worked' or 'failed.'