Persistent Hyperinsulinemic Hypoglycemia After Insulinoma Surgery: Diagnostic Impact of GLP‐1 Receptor PET/CT After Negative Conventional Imaging

Background: Localization of recurrent or residual insulinoma may be particularly challenging in postoperative setting, especially in the presence of postoperative anatomical distortion and inconclusive conventional imaging. Case presentation: A 71-year-old man developed recurrent endogenous hyperinsulinemic hypoglycemia following apparently curative surgical enucleation of a pancreatic insulinoma. The postoperative course was complicated by intra-abdominal hemorrhage and pseudocyst formation, resulting in marked anatomical distortion. Despite persistent biochemical evidence of insulinoma recurrence, serial contrast-enhanced computed tomography (CT) and 68Ga-DOTATOC PET/CT failed to identify residual disease. Subsequent glucagon-like peptide-1 receptor (GLP-1R) imaging with 68Ga-NODAGA-Exendin-4 PET/CT demonstrated focal tracer uptake in the pancreatic head, highly suggestive of recurrent or residual insulinoma. Endoscopic ultrasound (EUS) subsequently confirmed a small lesion in the uncinate process, which was successfully treated with EUS-guided radiofrequency ablation (EUS-RFA). Following the procedure, hypoglycemic episodes resolved, with normalization of glucose, insulin, and C-peptide levels and no signs of recurrence at follow-up. Conclusion: This case highlights the clinical value of GLP-1 receptor PET/CT for localizing insulinoma in the context of negative conventional or somatostatin receptor (SSTR)-based imaging. Accurate functional localization may directly guide minimally invasive therapeutic interventions and help avoid high-risk reoperative pancreatic surgery.