A rare case of post-gastric bypass hypoglycaemia

A 46-year-old woman with a history of Roux-en-Y gastric bypass (RYGB) surgery in 2010 was referred to the hepatobiliary oncology clinic in the University of Colorado Hospital in May 2013 with frequent episodes of post-prandial hypoglycaemia with neurogenic and neuroglycopenic symptoms. Findings in her biochemical profile, a 72-hour fast, and a mixed meal test were all negative. Subsequent CT abdomen and endoscopic ultrasound did not identify pancreatic lesions. Interventional radiology (IR) hepatic venous sampling with calcium gluconate localised excess insulin production to the tail of the pancreas. Medical management with acarbose and octreotide was commenced, but due to progressive symptoms and life-threatening episodes of hypoglycaemia, the pancreas was surgically resected. Pathology failed to show neoplastic tissue; histology demonstrated mild hyperplasia and hypertrophy, although within normal limits. A diagnosis of nesidioblastosis – a rare disease that causes pancreatic hyperfunction in the absence of an insulinoma and with evidence of hyperplasia – was made. It is a leading cause of hyperinsulinaemic hypoglycaemia in childhood, but causes <5% of cases in adults. Although the exact pathogenesis is not understood, nesidioblastosis is increasingly recognised as a late complication of bariatric surgery, where it is termed “post-gastric bypass hypoglycaemia” to distinguish from other entities associated with nesidioblastosis.