A 48-year-old man originally presented with a 5-day history of watery, nonbloody diarrhea without recent travel or contact with ill people. His medical history was significant for a prolonged course of Clostridium difficile diarrhea 1 year earlier. On physical exam, he had orthostatic hypotension, dry mucous membranes, mild right lower quadrant tenderness to palpation, and hyperactive bowel sounds. Laboratory testing revealed a sodium level of 130 mEq/L, a potassium level of 1.7 mEq/L, a chloride level of 102 mEq/L, a bicarbonate level of 13 mEq/L, a blood urea nitrogen level of 43 mg/dL, a creatinine level of 1.6 mg/dL, and a calcium level of 11.4 mg/dL. Despite several liters of IV hydration and aggressive potassium repletion, he remained severely hypokalemic with a potassium level of 1.5 mEq/L. He was admitted to the medical ICU for further resuscitation. Stool testing was negative for C. difficile and other infectious organisms. The patient's symptoms resolved before additional evaluation, and he was discharged with a presumed diagnosis of severe viral gastroenteritis. The patient returned 1 week later with recurrence of profuse diarrhea. His physical examination was notable for a blood pressure of 104/59 mm Hg (nonorthostatic) and a pulse of 106 beats/min, again with dry mucous membranes and mild tenderness to palpation of the right lower quadrant. Serum chemistry panel revealed a sodium level of 137 mEq/L, a potassium level of 2.3 mEq/L, a chloride level of 111 mEq/L, a bicarbonate level of 10 mEq/L, a blood urea nitrogen level of 38 mg/dL, a creatinine level of 2.3 mg/dL, and a calcium level of 10.4 mg/dL. Testing was again negative for an infectious source of diarrhea, and colonoscopy was not suggestive of inflammatory bowel disease. An abdominal CT revealed a 5-cm pancreatic tail mass. The patient was later found to have an elevated vasoactive intestinal peptide (VIP) level of 1,765 pg/mL (reference range, 0 to 60 pg/mL). Fecal osmolality was not obtained. The tumor was resected, and histology confirmed a neuroendocrine tumor.
Tryon, Connor; Jennifer Coffey; Lida Fatemi; and Patrick Rendon. "Clinical vignette: VIPoma as a cause of persistent diarrhea." (2014). https://digitalrepository.unm.edu/hostpitalmed_pubs/45