Insulinoma presenting with post-prandial hypoglycaemia following fundoplication

Insulinomas are rare neuroendocrine tumours that classically present with fasting hypoglycaemia. This case report discusses an uncommon and challenging case of insulinoma soon after upper gastrointestinal surgery. A 63-year-old man presented with 6 months of post-prandial hypoglycaemia beginning after a laparoscopic revision of Toupet fundoplication. Hyperinsulinaemic hypoglycaemia was confirmed during a spontaneous episode and in a mixed-meal test. Localisation studies including magnetic resonance imaging (MRI), endoscopic ultrasound (EUS) and gallium dotatate positron emission tomography ((68)Ga Dotatate PET) were consistent with a small insulinoma in the mid-body of the pancreas. The lesion was excised and histopathology was confirmed a localised well-differentiated neuroendocrine pancreatic neoplasm. There have been no significant episodes of hypoglycaemia since. This case highlights several key points. Insulinoma should be sought in proven post-prandial hyperinsulinaemic hypoglycaemia – even in the absence of fasting hypoglycaemia. The use of nuclear imaging targeting somatostatin and GLP1 receptors has improved accuracy of localisation. Despite these advances, accurate surgical resection can remain challenging. LEARNING POINTS: Hypoglycaemia is defined by Whipple’s triad and can be provoked by fasting or mixed-meal tests. Although uncommon, insulinomas can present with post-prandial hypoglycaemia. In hypoglycaemia following gastrointestinal surgery (i.e. bariatric surgery or less commonly Nissen fundoplication) dumping syndrome or non-insulinoma pancreatogenous hypoglycaemia syndrome (NIPHS) should be considered. Improved imaging techniques including MRI, endoscopic ultrasound and functional nuclear medicine scans aid localisation of insulinomas. Despite advances in imaging and surgical techniques, accurate resection of insulinomas remains challenging.