Insulinoma misdiagnosed as dumping syndrome after bariatric surgery

Late dumping syndrome is a possible side-effect of gastric bypass. Hypoglycemic symptoms may develop 3-4 hours after certain types of foods. There may exist patients, however, who present hypoglycemia in the absence of dumping syndrome. The presence of only mild symptoms of hypoglycemia may make the evaluation of these patients difficult and delay the identification of other possible sources of hyperinsulinemia, including an insulinoma.

A 65-year-old woman underwent gastric bypass for continued weight gain and morbid obesity. After surgery, the patient had repeated episodes of hypoglycemia, diagnosed at follow-up as late dumping syndrome. The persistence of hypoglycemic episodes after nutritional counseling and modifications in the feeding pattern led to consideration of an autonomous source of hyperinsulinemia, and MRI and CT identified insulinoma. After a laparotomy and pancreatic tumor resection, she remains free of symptoms.

Hypoglycemic episodes after obesity surgery are not always related to dumping syndrome. The persistence of hypoglycemia in spite of nutritional counseling should raise the possibility that there may exist other causes. Insulinoma, the most common cause of endogenous hyperinsulinemia, should be investigated in these patients, since it is a tumor that can be cured.