Nesidioblastosis: A Rare Case of Post Prandial Hypoglycemia in a Patient With Gastric Bypass Surgery

Abstract

A 46-year-old man with recurrent episodes of hypoglycemia for two-years admitted with recent worsening of symptoms that ranged from dizziness, diaphoresis and disorientation to seizures and loss of consciousness. His symptoms were mostly postprandial with low random home sugars (50-80 mg/dL) despite consuming sugary drinks and candies. History remarkable for Roux-en-Y gastric bypass (RYGB) surgery 5 years ago for obesity, anxiety disorder and daily alcohol use (40 g/day). Denied diabetes, use of diabetic medications or weight loss supplements. Unremarkable physical exam with normal mental status. Labs [Table 1] demonstrated elevated proinsulin and C-peptide levels with negative urine toxicology screen and sulfonylurea assay. CT scan of the head and abdomen were unremarkable. Gastroenterology (GI) was consulted for an evaluation with endoscopic ultrasound (EUS) to rule out insulinoma. Although insulinoma was the working diagnosis in-addition to other differential diagnoses as listed [Table 2], a negative monitored 72-hour fasting test [Fig. 1] without any symptomatic hypoglycemic episodes essentially ruled out insulinoma. Recurrent post-prandial hypoglycemia with neuroglycopenic symptoms in the setting of RYGB and endogenous hyperinsulinism with negative 72-hour fasting test suggested nesidioblastosis as the likely diagnosis. Our patient was managed with Diazoxide (3-8mg/kg/day divided into 3 doses) and, complex carbohydrates were added to his diet. His hypoglycemic symptoms improved at subsequent follow-ups. Nesidioblastosis is rare in adults and, seen in patients who had undergone gastric bypass surgery with etiology linked to persistent hyper-secretion of glucagon-likepeptide-1 causing beta cells hypertrophy. Post-prandial neuroglycopenia is a classic manifestation but can be challenging to diagnose due to its rarity and the difficulty to localize on imaging. Selective arterial calcium stimulation and venous sampling can confirm the diagnosis, invasively [1-3]. Often patients are referred to GI for evaluation with EUS, but with RYGB, EUS is technically not feasible to evaluate pancreas due to the altered anatomy. However, a certain diagnosis can be made based on the history, labs [Table 1] and a negative 72-hour fasting test without the need for invasive tests. With increasing prevalence of obesity and gastric bypass surgeries, we as gastroenterologists shall expect to see more of this rare, but interesting metabolic complication of gastric bypass surgery.Figure 1Reference: [1] Service, G.J., et al. N Engl J Med, 2005. 353(3): p. 249-54. [2]. Kellogg, T.A., et al. Surg Obes Relat Dis, 2008. 4(4): p. 492-9. [3] Ritz, P. and H. Hanaire. Diabetes Metab, 2011. 37(4): p. 274-81.Figure 2Figure 3