Pancreatic Uptake by F-18-FDOPA PET/CT in Patients With Hypoglycemia After Gastric Bypass Surgery Compared With Controls With or Without Carbidopa Pretreatment

Purpose: The use of 18Fluorine-labeled dihydroxy-phenyl-alanine (F-18-FDOPA) PET/CT in patients with hypoglycemia suspected to be caused by pancreatic disease can be helpful to localize the source of excess insulin production. In this setting, carbidopa pretreatment is not recommended. However, quantitative comparisons of pancreatic tracer uptake in patients with or without carbidopa pretreatment and in diffuse pancreatic disease are lacking. Therefore, we aimed to describe and quantify pancreatic F-18-FDOPA uptake in patients without pancreatic disease with or without carbidopa pretreatment and in patients with hypoglycemia after gastric bypass surgery.

Patients and Methods: This is a retrospective data analysis of F-18-FDOPA PET/CT scans performed at a university medical center in the period from 2009 to 2015. All scans were reconstructed and calculated based on the European Association of Nuclear Medicine/EANM Research Ltd guidelines. Of 358 patients without evidence of pancreatic disease or hypoglycemic disorders, 344 received carbidopa and 14 did not. Another 9 patients had post-gastric bypass hypoglycemia. The main outcome measurement was F-18-FDOPA SUVmax for pancreatic head, body, and tail regions.

Results: Carbidopa pretreated patients had a lower median SUVmax (-1.15, -1.20, and -0.84 in pancreatic head, body, and tail [all P <0.01]) than patients without carbidopa pretreatment. Patients with post-gastric bypass hypoglycemia scanned without carbidopa pretreatment had higher median SUVmax (+1.18, + 1.39, and + 1.63, all P <0.03) compared with controls without pretreatment.

Conclusions: Patients with post-gastric bypass hypoglycemia have increased uptake in all pancreatic regions. Carbidopa pretreatment lowers pancreatic F-18-FDOPA uptake in the nonaffected pancreas and may therefore mask disease activity in post-gastric bypass hypoglycemia.