VIPoma (Verner-Morrison syndrome)
VIPoma is a rare vasoactive intestinal peptide-secreting pancreatic neuroendocrine tumor that causes Verner-Morrison syndrome: massive watery diarrhea, hypokalemia, and achlorhydria (WDHA syndrome). Diagnosis rests on a markedly elevated serum VIP level with tumor localization on imaging; first-line management is fluid and electrolyte repletion plus octreotide, with surgical resection for localized disease.
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What this article covers
- Overview
VIPoma is a rare, usually pancreatic, neuroendocrine tumor that autonomously secretes vasoactive intestinal peptide (VIP), producing a distinctive secretory diarrhea syndrome.
- Epidemiology
Rarity: VIPoma is among the rarest functional pancreatic neuroendocrine tumors, far less common than insulinoma or gastrinoma.
- Risk factors
MEN1 mutation carriers: A germline MEN1 mutation predisposes to pancreatic neuroendocrine tumors, including VIPoma, alongside parathyroid and pituitary tumors, though VIPoma is an uncommon manifestation.
- Pathophysiology
Cell of origin: VIPoma arises from non-alpha, non-beta pancreatic islet cells (D1 cells), which normally contribute little circulating VIP; the tumor secretes VIP autonomously in large, unregulated quantities.
- Clinical features
Diarrhea: Chronic, watery, large-volume, odorless diarrhea is the dominant complaint, often exceeding 5 liters per day at its worst and persisting through fasting.
- Differential diagnosis
Carcinoid syndrome: Also causes flushing and watery diarrhea, but flushing is more prominent and episodic, urinary 5-hydroxyindoleacetic acid is elevated rather than VIP, and profound hypokalemia is less typical.
- Diagnosis
First, know what establishes the diagnosis: VIPoma is confirmed by a fasting serum VIP level markedly above 75 pg/mL in a patient with the clinical WDHA pattern, together with a pancreatic tumor found on subsequent workup.
- Management
First, resuscitate fluids and electrolytes: Begin intravenous isotonic crystalloid to replace ongoing stool losses and correct dehydration, with potassium and bicarbonate repletion guided by frequent…
- Complications
Dehydration and acute kidney injury: Ongoing multi-liter stool losses can produce prerenal azotemia and hypovolemic shock if fluid replacement lags.
- Prognosis
Localized disease: Complete surgical resection of a localized VIPoma offers the best chance of cure, with resolution of the diarrhea syndrome once the tumor is removed.
- Prevention
Early recognition: Checking a fasting VIP level in any patient with secretory diarrhea exceeding 1 L/day that persists despite a supervised fast avoids prolonged, unrecognized fluid and electrolyte loss.
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- Gastrinoma (Zollinger-Ellison syndrome)
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- Insulinoma
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- Carcinoid syndrome
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- Hypokalemia
Hypokalemia is a serum potassium level below 3.5 mEq/L, most often caused by gastrointestinal or renal potassium losses, and it produces weakness, ileus, and arrhythmia risk through altered membrane excitability. Diagnosis rests on the urine potassium-creatinine ratio to separate renal from extrarenal causes, and treatment is intravenous or oral potassium chloride, with concurrent magnesium repletion, dosed to severity and symptoms.