Adult-onset nesidioblastosis: a challenging diagnosis revealed by glucagon-like-peptide-1 receptor imaging

A 52-year-old female presented with recurrent episodes of fasting or post-absorptive hypoglycemia. A 72-h fasting test confirmed endogenous hyperinsulinemia. Conventional imaging was unremarkable. Selective pancreatic arterial calcium stimulation and hepatic venous sampling showed a maximum calcium-stimulated insulin concentration from several pancreatic areas, mainly the proximal splenic artery and the proximal gastroduodenal artery, suggesting the presence of one or more occult insulinoma(s) in the region of the pancreatic body. Ga-68-DOTA-exendin-4 PET/CT showed however generalized increased uptake in the pancreas and a diagnosis of nesidioblastosis was therefore suspected. The patient has been since successfully treated with dietetic measures and diazoxide. Treatment efficacy was confirmed by a flash glucose monitoring system with a follow-up of 7 months. Learning points Adult nesidioblastosis is a rare cause of endogenous hyperinsulinemic hypoglycemia. The distinction between insulinoma and nesidioblastosis is essential since the therapeutic strategies are different. 68Ga-DOTA-exendin-4 PET/CT emerges as a new noninvasive diagnostic tool for the localization of an endogenous source of hyperinsulinemic hypoglycemia. Medical management with dietetic measures and diazoxide need to be considered as a valuable option to treat patients with adult nesidioblastosis. Flash glucose monitoring system is helpful for the evaluation of treatment efficacy.