Pheochromocytoma Producing Vasoactive Intestinal Peptide

The syndrome of watery diarrhea associated with hypokalemia and achlorhydria was originally described in 1958. Subsequently, this syndrome was shown to be caused by a neuroendocrine tumor secreting vasoactive intestinal peptide (VIP), and such tumors are almost always pancreatic in origin. We describe the case of a 78-year-old woman with gradual onset of hypokalemia, watery diarrhea, and weight loss. After a left adrenal mass was discovered, the patient chose medical therapy over surgical intervention. Initially her condition responded, then gradually became refractory to medical therapy. She had elevated levels of VIP, pancreatic polypeptide, dopamine, and vanillylmandelic acid. Subsequently, the patient underwent surgical excision of the mass that was found to be a VIP-producing pheochromocytoma. After surgery her diarrhea subsided, and her electrolytes and affected neuroendocrine hormone levels normalized.