VIPomas
Related Subjects:
|Zollinger Ellison syndrome
|VIPomas
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.
