Vasoactive Intestinal Peptide Tumor (VIPoma)

The VIPoma syndrome termed pancreatic cholera because the observed severe diarrhea resembled Vibrio cholera disease. The acronym WDHHA (watery diarrhea [100%], hypokalemia [100%], achlorhydria) and acidosis from bicarbonate wasting is often present for 3 or 4 years before diagnosis, with volumes usually exceeding 6 to 8 L of stool every 24 hours. Flushing and hypercalcemia are frequent but tetany can occur which may be due to hypomagnesemia. Other features include abnormal glucose tolerance, and dilation of the gallbladder. Tumors secreting VIP usually originate in the pancreas or along the sympathetic chain as ganglioneuroblastomas, neurofibromas, and pheochromocytomas as well as throughout the gut, skin and bone marrow. VIP is not the only agent implicated in the diarrhea syndrome. Gastrin, secretin, glucagon, enteroglucagon, GIP, PP, VIP, thyrocalcitonin (TCT), prostaglandins, and peptide fragments of pre-pro VIP or any one of a number of combinations have been implicated as possible etiologic agents of the diarrhea syndrome. Clinically the secretory nature of this syndrome is exemplified by diarrhea that persists with fasting! Tumors can be localized by ultrasound if large, CT, celiac, superior mesenteric angiography and renal angiograpy and if negative transhepatic portal venous sampling. Initial treatment should be correction of fluid and electrolyte loss. Primary treatment should be surgical excision or debulking followed by somatostatin analog therapy which may control the secretions as well as the tumor growth. There appears to be little difference in the tumor response to lanreotide, interferon or both and PRRT which has been shown to improve quality of life. In advance metastatic disease positive reports have been published using tyrosine kinase inhibitors (sunitinib) and MTOR inhibitors (everolimus) with an increase of the progression free survival by up to 18 months.