What are the features of a VIPoma?
The main clinical features of VIPoma are listed below:
- Watery diarrhoea
- Hypokalaemia
- Achlorhydria
- Facial flushing
- Dehydration
- Hypercalcaemia
- Weakness
- Abdominal pain
- Weight loss
This condition is sometimes referred to as 'pancreatic cholera' because its main clinical features is profuse diarrhoea. The diarrhoea tends to occur intermittently at first, but as the tumour grows the diarrhoea becomes continuous. The volume excreted exceeds 3 litres per day in 80% of patients, and it has been known to reach 20 litres in some. This contains a large amount of electrolytes (potassium and bicarbonate), leading to hypokalaemia (low blood potassium content). This is worsened by the release of aldosterone to combat the fluid loss, the result of which is further potassium excretion. Low blood potassium can lead to cardiac arrhythmias and, in severe cases, death.
Achlorhydria (no acid production in the stomach) is seen in 30% of patients, with a further 30% suffering from hypochlorhydria (low acid production). All these features form the characteristic WDHA (Watery Diarrhoea, Hypokalaemia, and Achlorhydria) which is often used to describe VIPoma syndrome.
Hypercalcaemia is also a feature, although its cause is uncertain. It could be due to parathyroid hormone related protein (PTHrP), or it could be due to parathyroid hormone released as part of MEN 1, or dehydration. Dehydration may also lead to hypovolemia, which can in some cases lead to renal failure. Hypomagnesaemia has been known to occur in VIPoma, and this can lead to tetany (twitching of muscles).
The role of VIP as a muscle relaxant can be seen in a VIPoma crisis, where severe hypotension (low blood pressure) may occur due to relaxation of smooth muscle of the vessels. This worsens the hypovolemic effect of dehydration.
Other common features include facial flushing (in 20% of cases), weakness, abdominal pain and weight loss.