Makindo Medical Notes

Both VIPomas and villous adenomas can cause profuse watery diarrhoea 💧 and hypokalaemia 🔋 depletion.

📖 About

• VIPomas are very rare pancreatic neuroendocrine tumours that secrete vasoactive intestinal peptide (VIP).
• They classically present with WDHA syndrome:
  • Watery diarrhoea 💧 (secretory, large-volume)
  • Hypokalaemia 🔋
  • Achlorhydria 🧪 (gastric acid suppression)
• Most arise in the pancreatic tail, though ectopic sites (adrenal, sympathetic chain) are reported.
• Associated gene location: VIP gene on chromosome 6.

🦠 Aetiology & Pathophysiology

• VIP acts via cAMP, stimulating intestinal chloride and water secretion → secretory diarrhoea.
• Chronic secretion causes profound fluid & potassium loss, leading to dehydration, acidosis, and weakness.
• Rarely, other peptide-secreting tumours (e.g., ganglioneuroblastomas) can mimic VIPoma syndrome.

🔍 Clinical Features

• Profuse watery diarrhoea (>3L/day), persists during fasting.
• Hypokalaemia: muscle weakness, cramps, lethargy.
• Weight loss and cachexia due to chronic fluid loss.
• Facial flushing in some patients (carcinoid-like feature).
• Hepatomegaly may indicate liver metastases at presentation.

🧪 Investigations

• Bloods:
  • U&E: low potassium, non-anion gap metabolic acidosis (loss of HCO₃⁻ in stool).
  • Mild hyperglycaemia due to impaired insulin secretion.
• Plasma VIP level: diagnostic when markedly elevated.
• Neuroendocrine markers: ↑ pancreatic polypeptide, chromogranin A.
• Imaging (CT/MRI ± PET with somatostatin analogue): localises tumour and detects metastases.

💊 Management

• Stabilisation: Aggressive IV fluids + potassium replacement.
• Octreotide (somatostatin analogue) — suppresses VIP release, improves diarrhoea.
• Definitive therapy: Surgical resection if localised.
• Metastatic disease: debulking, hepatic resection/embolisation, or targeted therapies; otherwise palliative care with symptom control.

📌 Exam Pearls

• 💡 Always think of VIPoma when you see secretory diarrhoea + hypokalaemia + metabolic acidosis that continues despite fasting.
• 💡 Villous adenomas of the colon can mimic this with hypokalaemic diarrhoea → a favourite comparison point.
• 💡 Octreotide is both diagnostic (improvement in symptoms) and therapeutic.