Roughly 50–75% of VIPomas are malignant, but even when they are benign, they are problematic because they tend to cause a specific syndrome: the massive amounts of VIP cause a syndrome of profound and chronic watery diarrhea and resultant dehydration, hypokalemia, achlorhydria, acidosis, flushing and hypotension (from vasodilation), hypercalcemia, and hyperglycemia.
[4] The major clinical features are prolonged watery diarrhea (fasting stool volume > 750 to 1000 mL/day) and symptoms of hypokalemia and dehydration.
Lethargy, muscle weakness, nausea, vomiting and crampy abdominal pain are frequent symptoms.
[5] Besides the clinical picture, fasting VIP plasma level may confirm the diagnosis, and CT scan and somatostatin receptor scintigraphy are used to localise the tumor, which is usually metastatic at presentation.
[citation needed] For metastatic disease, peptide receptor radionuclide therapy (PRRT) can be highly effective.