VIPoma

• • A non-beta islet cell tumor of the pancreas that secretes VIP

  • VIPomas cause the WDHH syndrome (watery diarrhea, hypokalemia, hypochlorhydria)

  • Chronic profuse watery diarrhea

  • Massive fecal loss of potassium

  • Low serum potassium

  • Extreme weakness

  • Elevated serum vasoactive intestinal polypeptide (VIP) level

Epidemiology

• • Approximately 80% of the tumors are solitary, located in the body or tail of the pancreas

  • About 50% of the lesions are malignant, and 75% of those have metastasized by the time of exploration.

  • Mean age of presentation is 47 years; women are affected 3 times as often as men

Symptoms and Signs

• • Profuse watery diarrhea

  • Extreme weakness

Laboratory Findings

• • Elevated fasting VIP levels (> 190 pg/mL)

  • Low serum potassium

  • Severe metabolic acidosis results from loss of HCO3 in the stool

  • Elevated serum calcium, possibly from secretion by the tumor of a parathyroid hormone-like substance

  • Mild hyperglycemia

  • Hypochlorhydria

Imaging Findings

• • CT scan or MRI is the best initial imaging test for localization and metastases

  • Somatostatin receptor scintigraphy is also useful for localization

• • Severe chronic watery diarrhea along with metabolic acidosis and hypokalemia may prompt investigation for VIPoma

  • Severe secretory diarrhea, elevated serum VIP level and pancreatic mass suggests diagnosis

Rule Out

• • Patients who complain of severe diarrhea must be evaluated carefully for other causes before seriously considering the diagnosis of VIPoma

  • Gastrinoma

  • Carcinoid

  • Medullary thyroid tumor

• • Documentation of severe, watery diarrhea (stool volume averages about 5 L/d during acute episodes)

  • Serum VIP level

  • CT scan or MRI

  • Somatostatin receptor scintigraphy if not detected by CT scan or MRI

When to Admit

• • Severe metabolic acidosis

  • Severe hypokalemia

• • Octreotide for palliation of symptoms.

Surgery

• • Resection of entire tumor

  • -Pancreaticoduodenectomy for tumor in head of pancreas

    -Distal pancreatectomy for tumor in body and tail

  • Palliative debulking of metastases

Indications

• • All cases in which resection is technically feasible

Medications

• • Long-acting somatostatin analogs decrease VIP levels, controls diarrhea, and may even reduce tumor size

  • Streptozocin if not completely resected

Prognosis

• • 1-year survival is 40% in patients whose tumors cannot be completely resected

References