A 46-year-old man with profuse diarrhoea was admitted for measurement of his daily stool weight for 3 days

A 46-year-old man with profuse diarrhoea was admitted for measurement of his daily stool weight for 3 days, with a further measurement on day 4 when fasting. He had previously had a normal colonoscopy and small bowel meal. his serum potassium level is 2.4 mmol/L (3.5–4.9)

daily stool weight:
day 1 1450 g (<200)
day 2 1200 g
day 3 1560 g
day 4 (fasting) 1400 g
What is the most likely diagnosis?

Question 25
A: coeliac disease
B: irritable bowel syndrome
C: lactose intolerance
D: pancreatic insufficiency
E: VIPoma

aNS: E: VIPoma