VIPoma and WDHA Syndrome
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Direct answer
Rare neuroendocrine tumours of the pancreatic body or tail that secrete vasoactive intestinal peptide cause VIPoma and its WDHA syndrome — watery diarrhoea, hypokalaemia and achlorhydria — also called Verner-Morrison syndrome or pancreatic cholera. The diarrhoea is secretory and prodigious: more than a litre (often 3 litres or more) of tea-coloured stool daily, persisting unchanged during fasting, with profound hypokalaemia (sometimes below 2.5 mmol/L), metabolic acidosis from stool bicarbonate loss, flushing in some, and hypo- or achlorhydria from VIP inhibition of acid secretion. Diagnosis rests on fasting VIP levels — clearly elevated (thresholds vary by assay, commonly quoted above 75 up to above 190 pg/mL, with values above 500 classic) — plus CT or MRI and somatostatin-receptor imaging. Octreotide controls the diarrhoea and potassium loss in most patients; resection — distal pancreatectomy or enucleation — cures localised disease, with metastatic cases managed by debulking, ablation and somatostatin analogues.
What you must remember
- The acronym is the checklist: WDHA — watery diarrhoea (secretory, fasting-invariant), hypokalaemia (stool potassium loss, dangerous arrhythmia territory), achlorhydria or hypochlorhydria; VIP also causes hyperglycaemia, hypercalcaemia and flushing in a minority — the "pancreatic cholera" picture.
- Site and behaviour: most VIPomas arise in the pancreatic body-tail; roughly half to two-thirds are malignant at diagnosis (hepatic metastases common), distinguishing it from insulinoma, which is malignant in only about a tenth.
- Diagnostic test pairing: fasting serum VIP during active diarrhoea — assay-dependent cut-offs (above 75-190 pg/mL commonly cited; higher values more specific) — plus stool volume documentation; exclude other secretory diarrhoeas (gastrinoma — acidic and ulcerating; carcinoid with 5-HIAA; laxative abuse).
- First drug to reach for: octreotide, a somatostatin analogue, binds tumour receptors and shuts off VIP release — controlling fluid and electrolyte losses before, after and instead of surgery; prednisone and loperamide-class agents are weak adjuncts.
- Fluid and electrolyte rescue: patients arrive dry, hypokalaemic and acidotic — litres of saline with aggressive potassium replacement precede any imaging adventure; death historically was from hypokalaemia, not tumour.
- Operation for localised disease: distal pancreatectomy for body-tail tumours, enucleation for small favourable lesions away from the duct; intraoperative palpation and ultrasound because multiplicity occurs.
- Advanced disease strategy: cytoreductive surgery, radiofrequency ablation of liver metastases, everolimus or streptozocin-based chemotherapy, peptide receptor radionuclide therapy — VIPomas overexpress somatostatin receptors, which both images and treats them.
A typical exam case
A 55-year-old woman is admitted after three months of six to ten watery stools daily, 4 kilograms of weight loss, and two near-syncope episodes. Potassium is 2.1 mmol/L with bicarbonate of 14, glucose mildly raised. The stool is large-volume and remains voluminous during a 48-hour fast — the single bedside observation that excludes osmotic diarrhoea. Fasting VIP returns markedly elevated. After fluid and potassium resuscitation and octreotide 100 micrograms thrice daily, the diarrhoea slows within 48 hours — a diagnostic-therapeutic response in itself. CT shows a 5-centimetre pancreatic tail tumour with two liver lesions; DOTATATE PET confirms receptor expression. She undergoes distal pancreatectomy with wedge ablation of the metastases, continues depot octreotide, and her potassium normalises. The alternative presentation — the same chemistry with no lesion on CT — is investigated with endoscopic ultrasound and somatostatin imaging, remembering the rare extra-pancreatic VIPoma in ganglioneuroma-spectrum tumours, particularly in children.
Where students slip
Examiners contrast the pancreatic endocrine tumours by their "signature secretion": insulinoma — hypoglycaemia with Whipple's triad; gastrinoma — acid ulcers; VIPoma — water and potassium; glucagonoma — migratory necrolytic erythema with diabetes; somatostatinoma — gallstones, steatorrhoea and diabetes. A watery-diarrhoea stem with hypokalaemia expects VIPoma, and the mark is lost only if the candidate forgets the achlorhydria component or calls the diarrhoea osmotic. The second trap is the potassium — the exam wants the candidate to treat hypokalaemia as the immediate threat, before VIP levels return. Third, behaviour: VIPoma is malignant in over half, so an MCQ pairing it with "usually benign" (true for insulinoma) is wrong.
Frequently asked questions
What does WDHA stand for?
Watery diarrhoea, hypokalaemia and achlorhydria — the triad produced by VIP-secreting tumours, also known as Verner-Morrison syndrome or pancreatic cholera.
How is VIPoma diarrhoea characterised?
Large-volume secretory watery diarrhoea — typically over a litre, often several litres daily — that persists during fasting, distinguishing it from osmotic diarrhoea which stops with nil-by-mouth.
What laboratory test confirms VIPoma?
A clearly elevated fasting serum VIP level during active diarrhoea, with assay-dependent thresholds (commonly above 75-190 pg/mL), supported by hypokalaemia and metabolic acidosis.
Why is octreotide central to management?
Somatostatin analogue therapy switches off VIP release from receptor-expressing tumour, controlling the life-threatening fluid and potassium losses before surgery and long term in unresectable disease.
What operation cures a localised pancreatic VIPoma?
Distal pancreatectomy for body-tail tumours or enucleation for small lesions away from the pancreatic duct, after octreotide and electrolyte stabilisation.