Chronic Diarrhea Secondary to Newly Diagnosed VIPoma

Vasoactive intestinal polypeptide-secreting tumors (VIPoma) are a rare pancreatic neuroendocrine tumor that can cause chronic diarrhea with 1 case per 10 million people per year. Diagnosis is made based on a combination of laboratory evaluation (serum VIP level), imaging findings (functional positron emission tomography-computed tomography [PET-CT]), and histological analysis (chromogranin A stain). We present a case of a male with 6 months of diarrhea and malaise who was found to have significant kidney injury and hypokalemia requiring admission to the medical intensive care unit. Subsequent laboratory evaluation while admitted eventually showed a low stool osmotic gap (–11 mOsm/kg) consistent with secretory diarrhea, in addition to significantly elevated VIP levels at 940 pg/mL (normal <75). Cross-sectional imaging with functional Gallium-68 dotatate PET-CT confirmed metastatic functional neuroendocrine tumor indicative of a VIPoma. Pathology on subsequent metastatic liver lesion aspiration was consistent with a well-differentiated VIPoma, and symptoms dramatically improved following initiation of octreotide therapy.