SAT158 Hypoglycemia After Bariatric Surgery Caused By Insulinoma

Disclosure: A. Yaseen: None. H. Lam: None. Introduction: Post bariatric surgery hypoglycemia occurs at least 6 to 12 months after bariatric surgery, presents as postprandial neuroglycopenia with documented blood glucose <54 mg/dl occurring 1 to 3 hours after meals, resolving with carbohydrate intake, and normal fasting glucose. Fasting hypoglycemia or hypoglycemia > 4 hours after caloric intake is not typical of post-bariatric hypoglycemia and should raise concern for other etiologies, specifically insulinoma. Clinical Case: A 62 year old female who had Roux-en-Y gastric bypass (RYGB) surgery 18 years ago presented with confusion and a blood glucose level of 35 mg/dl.She had been having episodic hypoglycemia fasting and nonfasting for 4 years prior to presentation. Initial workup revealed serum insulin 10 uIU/ml, C-peptide 2.3 ng/ml, and serum glucose of 19 mg/dl. A dextrose 20% in water intravenous infusion was started in addition to octreotide injections, acarbose, and diazoxide. Prednisone was added later and acarbose discontinued. Magnetic resonance imaging of the abdomen and magnetic resonance cholangiopancreatography showed a 1.8 x 1.3 cm enhancing lesion within the pancreatic tail. Selective arteriography and intra-arterial calcium stimulation with hepatic venous sampling revealed significant elevation of insulin after calcium gluconate injection into the accessory pancreatic tail artery arising from the superior mesenteric artery which supplies the hypervascular pancreatic tail mass. Patient had an exploratory laparotomy and splenic preserving distal pancreatectomy. Surgical pathology revealed a 2.1 cm grade 1, well-differentiated neuroendocrine tumor that was limited to the pancreas. Hypoglycemia resolved after surgery and she was discharged on glargine insulin and metformin. 1 month after surgery, C-peptide was 0.3 ng/ml, serum glucose was 101 mg/dl and HbA1c was 6.5%. Discussion and Conclusion: The incidence of hypoglycemia after RYGB is uncertain but has been reported to be 0.1 to 0.4% of cases. Only 9 cases of insulinoma in patients with a history of gastric surgery have been reported, 7 of 9 (78%) being female with an average age of 56 years old. Symptoms included fasting and postprandial hypoglycemia occurring 6 months to 20 years after bariatric surgery. CT, MRI, and endoscopic ultrasound have been found to have excellent sensitivity for preoperative localization of insulinoma. Selective arteriography and intra-arterial calcium stimulation with hepatic venous sampling is recommended when non-invasive imaging modalities fail to localize the tumor. Surgical resection remains the mainstay for cure. Dietary modification and pharmacological therapy with diazoxide or somatostatin analogues are used in poor surgical candidates. Insulinoma after RYGB is rare, but needs to be considered in patients with hypoglycemia occurring in the fasting state, as this is atypical for post-bariatric hypoglycemia Presentation: Saturday, June 17, 2023