Vasoactive Intestinal Polypeptide Secreting Tumor - VIPoma

 

Clinical Background

Vasoactive intestinal polypeptide secreting tumor (VIPoma) is a rare pancreatic neuroendocrine tumor associated with profuse diarrhea.

Epidemiology

  • Incidence – 1/10,000,000
  • Age – median onset is 40s
  • Sex – M:F, equal
  • Occurrence – sporadic, although some occur in association with multiple endocrine neoplasia type 1 (MEN1)
  • 60-80% of patients have metastatic disease at presentation

Risk Factors

  • Genetic – around 5% associated with MEN 1

Pathophysiology

  • Most tumors occur in the body and tail of the pancreas and are unifocal
  • Symptoms result from the secretion of vasoactive intestinal polypeptide (VIP)
    • VIP is an amino acid polypeptide that binds to intestinal epithelial cells and activates cellular adenylate cyclase and cyclic adenosine monophosphate (cAMP )
  • Other tumors that can produce VIP include ganglioneuroblastoma, bronchogenic carcinoma, pheochromocytoma, medullary thyroid carcinoma

Clinical Presentation

  • Verner-Morrison syndrome
    • Chronic watery diarrhea, hypokalemia and achlorhydria (WDHA )
    • Profuse diarrhea (patients may exceed 6-8 L/day) causing dehydration, metabolic acidosis and renal failure

Treatment

  • Symptom control
  • Somatostatin analogues
  • Resection