Nesidioblastosis: an uncommon complication seen post Roux-en-Y gastric bypass

SUMMARY: Adult-onset nesidioblastosis is a rare complication of Roux-en-Y gastric bypass surgery and may occur months to years after the initial surgical procedure. It is manifested by a hyperinsulinemic, hypoglycemic state. The annual incidence of adult-onset hyperinsulinemic hypoglycemia is believed to be less than 0.1 in 1 000 000 with a mean age of onset of 47 years (1). Here, we describe a patient who presented with worsening hypoglycemic symptoms for 1 year prior to presentation that eventually progressed to hypoglycemic seizures. The onset of this hypoglycemia was 5 years after Roux-en-Y gastric bypass surgery. A full neurological evaluation, which included an EEG, head CT, and MRI, was performed to rule out epilepsy and other seizure-related disorders. After hypoglycemia was confirmed, extensive laboratory studies were obtained to elucidate the cause of the hypoglycemia and differentiate nesidioblastosis from insulinoma. Once the diagnosis of nesidioblastosis was established, a sub-total pancreatectomy was performed, and the patient was discharged and placed on acarbose, a competitive reversible inhibitor of pancreatic α-amylase and intestinal brush border α-glucosidases which slows carbohydrate absorption. The lack of information and understanding of nesidioblastosis due to its rarity makes any knowledge of this rare but important surgical complication essential. As incidence of obesity increases, the number of gastric bypasses being performed increases with it, and understanding this disease process will be essential for the primary care provider. This is the primary reason for the writing of this publication. LEARNING POINTS: Nesidioblastosis is a persistent hyperinsulinemic, hypoglycemic state, mostly seen after Roux-en-Y gastric bypass surgery, with symptoms occurring postprandially. The incidence is 0.1–0.3% of all post Roux-en-Y gastric bypass patients. The key diagnostic clue to identifying nesidioblastosis is a positive selective arterial calcium stimulation test, showing a diffuse pattern of increased basal hepatic venous insulin concentration, whereas insulinomas would show focal increases. Pathological specimen of pancreas will show diffuse hypertrophy of beta cells. Management includes acarbose and total or subtotal pancreatectomy, which can be curative. With the prevalence of obesity increasing and more patients turning to Roux-en-Y gastric bypass, more patients may be at risk of this potential surgical complication.