LBSUN345 Diagnostic Dilemma In A Case of Vipoma

INTRODUCTION: Vasoactive intestinal polypeptide secreting tumors (VIPoma) are rare neuroendocrine tumors that have nonspecific features of watery diarrhea, hypokalemia and achlorhydria. With an incidence of 1 in a million per year, it is diagnosed based on serum VIP levels (>75pg/ml) followed by imaging studies to localize the tumor and look for metastases. We present a challenging case of VIPoma that was successfully managed with surgical exploration despite classic yet nonspecific clinical features and poor evidence on imaging. CASE DISCUSSION: A 78-year-old Caucasian woman presented with persistent secretory diarrhea for 2 months. Past medical history was significant for intractable peptic ulcer disease and Billroth II reconstruction. Laboratory investigations showed severe hypokalemia (2.1 mmol/l), serum bicarbonate 13 and chloride 117. Blood glucose and calcium levels were within normal range. Stool studies confirmed secretory diarrhea with stool osmotic gap of 10 mOsm/kg but no growth. Serum gastrin, parathyroid hormone, chromogranin and urine 24-hour 5-hydroxy indoleacetic acid (5-HIAA) levels were within normal limits. Plasma VIP levels were elevated at 79 pg/mL. Computed tomography of the abdomen and pelvis did not show any evidence of pancreatic tumor or biliary ductal dilatation. Endoscopic ultrasound could not fully evaluate the head of pancreas but showed unremarkable liver, pancreatic body and tail. Capsule endoscopy was unremarkable as well. An octreotide scan, however, demonstrated increased activity near the head of the pancreas and abdominal aorta. As clinical picture and octreotide scan findings were consistent with VIPoma, operative exploration for possible pancreaticoduodenectomy was pursued. No evidence of palpable or occult metastatic disease was found; but intraoperative color doppler ultrasound localized two lesions less than 1 cm in size at the level of the uncinate process and ampulla. An open pancreaticoduodenectomy was performed and the existing Billroth II anatomy was modified to accommodate pancreatojejunostomy, gastrojejunostomy and choledochojejunstomy. A jejunostomy tube was placed for enteral access. At 2-month post-operative follow-up, the patient had significant improvement of his diarrhea. Radiographic resolution was noted on repeat octreotide scan 4 months following resection. CONCLUSION: VIPomas are usually diagnosed by elevated VIP levels and imaging studies are used to localize the tumor for further treatment. However, this case highlights that in secretory diarrhea with elevated VIP level and no alternate diagnosis, despite negative imaging studies further exploration with octreotide scan is warranted. Surgical exploration may show the site of lesion and appropriate surgical intervention may lead to resolution of VIPoma. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.