Insulinoma unmasked by bariatric surgery

Abstract

Introduction: Hypoglycemia is a known complication of bariatric surgery and it is attributed to several mechanisms one of them is islet cell hyperplasia (1). To our knowledge there are just few reported cases in the literature of confirmed insulinoma discovered after bariatric surgery (2). Clinical case: A 42 year old man morbidly obese underwent biliopancreatic diversion, four months later and after losing twenty kilograms of his weight he started to have repeated episodes of sever hypoglycemia almost always induced by fasting with confirmed low blood sugar level as low as 1.6 mmol/liter with history of loss of consciousness several times in two months period. Two weeks before he undergoes the ultimate management his hypoglycemia was persistent and he needed to be admitted and kept on contentious intravenous infusion of D10 % to maintain his blood sugar just above 4 mmol/liter. His physical examination was unremarkable apart from obesity with BMI of 51 kg/m2. His laboratory workup after stopping intravenous dextrose for five minutes was consistent with endogenous insulin induced hypoglycemia : blood sugar 2mmol/liter (n 3.9-6.1), insulin 157 pmol/liter (n 43-193), CPeptide 2521 pm/liter (n 260-1390), proinsulin 1100 pmol/liter (n 3-20), screening for serum sulfonylurea and meglitinides were negative. The rest of his blood works include: Am cortisol 282 nmol/liter (n 138-635), kidney and liver functions were normal. CT scan of abdomen showed 2x1.6 cm tumor at the body of the pancreas which was resected laproscopically and patient blood sugar normalized within minutes intraoperatively. The Histopathology examination confirmed that the mass was insulinoma. The patient remains free of symptoms after one year of follow up. Conclusion: We report a very rare case of insulinoma that was unmasked by biliopancreatic diversion and we believe such an etiology should be considered in workup of post bariatric hypoglycemia.