VIPomas

Vasoactive intestinal polypeptide (VIP) secreting tumours are rare neuroendocrine tumours. The associated syndrome was first described by Priest and Alexander in 1957. They reported a case that they thought to be a variant of the Zollinger–Ellison syndrome—a patient with an islet cell tumour associated with diarrhoea, peptic ulceration, and hypokalaemia (1). The following year, Verner and Morrison described a syndrome of profuse, refractory, watery diarrhoea with severe hypokalaemia and dehydration associated with a non-β-cell islet cell tumour (2). Historical terms for this syndrome have included ‘pancreatic cholera’ (as the diarrhoea is similar to the secretory diarrhoea observed in cholera) and the acronym WDHA (watery diarrhoea, hypokalaemia, and achlorhydria). However, these terms are inaccurate descriptions of a syndrome that can be associated with both extrapancreatic tumours and normal gastric acid secretion. In 1973, Bloom first connected the watery diarrhoea with an elevated plasma VIP level and an increased tumour content of VIP, suggesting the term ‘VIPoma syndrome’ (3). There followed a debate as to whether VIP was a marker for the syndrome or the causative agent for the diarrhoea. However, in 1983, Kane infused porcine VIP intravenously in healthy human subjects, achieving VIP levels similar to patients with VIPomas. Profuse watery diarrhoea developed within 4 h of infusion, providing evidence that VIP was indeed the mediator of the syndrome (4).