Functional Imaging in Hyperinsulinemic Hypoglycemia after Gastric Bypass Surgery for Morbid Obesity

Context: Hyperinsulinemic hypoglycemia after Roux-en-Y gastric bypass (RYGB) has been increasingly reported. It is induced by beta-cell hyperplasia often referred to as nesidioblastosis. Positron emission tomography (PET) with [11C]-5-hydroxytryptophan (C-11-HTP) and 6-[18F]fluoro-3,4-dihydroxy-L-phenylalanine (F-18-DOPA) has been successfully applied to image neuroendocrine tumors. No data are available of the usefulness of these functional imaging techniques in post-RYGB in this new endocrine disorder, neither for diagnostic purposes nor for follow-up.

Objective: We present a patient with post-RYGB hypoglycemia who underwent C-11-HTP and F-18-DOPA PET scintigraphy for diagnostic purposes and to evaluate the effect of additional laparoscopic adjustable banding of the pouch as a surgical therapy for this disorder.

Patient: We describe a woman with biochemically confirmed post-RYGB hypoglycemia who showed diffuse uptake of the C-11-HTP and F-18-DOPA tracers in the entire pancreas. After failure of dietary and medical treatment options, she underwent a laparoscopic adjustable banding for pouch dilatation. Subjective improvement was noted, which coincided with decreased uptake of F-18-DOPA and C-11-HTP in the head of the pancreas.

Conclusions: Functional imaging by F-18-DOPA- and C-11-HTP-PET can accurately visualize diffuse endocrine pancreatic activity in post-gastric bypass hyperinsulinemic hypoglycemia. Both C-11-HTP- and F-18-DOPA-PET imaging appear to have a similar diagnostic performance in the presented case, and uptake of both tracers potentially relates to disease activity after surgical intervention. (J Clin Endocrinol Metab 97: E963-E967, 2012)