VIPoma

A VIPoma (also known as Verner Morrison syndrome, after the physicians who first described it ) is a rare (1 per 10,000,000 per year) endocrine tumor, usually (about 90%) originating in the pancreas, that produces vasoactive intestinal peptide (VIP).

A syndrome caused by non-β islet cell tumors. It may be associated with multiple endocrine neoplasia type 1.

The massive amounts of VIP in turn cause profound and chronic watery diarrhea and resultant dehydration, hypokalemia, achlorhydria (hence WDHA-syndrome, or pancreatic cholera syndrome), acidosis, vasodilation (flushing and hypotension), hypercalcemia and hyperglycemia.

Symptoms and Signs
The major clinical features are prolonged watery diarrhea (fasting stool volume > 750 to 1000 mL/day) and symptoms of hypokalemia and dehydration. Half of the patients have relatively constant diarrhea while the rest have alternating periods of severe and moderate diarrhea. One third have diarrhea < 1yr before diagnosis, but in 25%, diarrhea is present for 5 yr or more before diagnosis. Lethargy, muscle weakness, nausea, vomiting and crampy abdominal pain are frequent symptoms. Hypokalemia and impaired glucose tolerance occur in < 50% of patients. Achlorhydria is also a feature. During attacks of diarrhea, flushing similar to the carcinoid syndrome occur rarely.

Diagnosis
Besides the clinical picture, fasting VIP plasma dosage may confirm the diagnosis, and CT scan and somatostatin receptor scintigraphy are used to localise the tumor, which is usually metastatic at presentation.

Treatment
Besides treating the water and electrolyte abnormalities, octreotide (a somatostatin analogue) can be used to temper symptoms. Surgery is the only curative option.