From the Guidelines
Vipoma causes achlorhydria due to the excessive secretion of vasoactive intestinal peptide (VIP), which strongly inhibits gastric acid production. This occurs through multiple mechanisms, including the activation of adenylate cyclase in parietal cells, reduction of histamine release from enterochromaffin-like cells, and counteraction of the acid-stimulating effects of gastrin, as well as the promotion of bicarbonate and water secretion from the pancreas and intestines, leading to a neutralization of any acid produced 1. The clinical presentation of vipoma syndrome, also known as WDHA syndrome (watery diarrhea, hypokalemia, and achlorhydria), is characterized by severe diarrhea, hypokalemia, and achlorhydria, which can be life-threatening if left untreated 1. Key features of the syndrome include:
- Watery diarrhea
- Hypokalemia
- Achlorhydria Treatment of vipoma syndrome often involves rehydration and the use of somatostatin analogues, which can dramatically improve the clinical condition by reducing diarrhea and normalizing vasoactive intestinal peptide levels 1. The dose of somatostatin analogues can be titrated against vasoactive intestinal peptide levels, with the goal of normalizing these levels and alleviating symptoms 1.
From the Research
VIPoma and Achlorhydria
- VIPoma is a rare pancreatic endocrine tumor that secretes excessive amounts of VIP (Vasoactive Intestinal Peptide), causing a clinical syndrome characterized by secretory diarrhea, hypokalemia, and achlorhydria 2, 3, 4, 5.
- The excessive secretion of VIP leads to achlorhydria, which is a condition where the stomach does not produce enough hydrochloric acid 2, 3, 4, 5.
- The exact mechanism of how VIP causes achlorhydria is not fully understood, but it is thought to be related to the inhibitory effect of VIP on gastric acid secretion 6.
Pathophysiology of VIPoma
- VIPomas are typically malignant and have already metastasized at the time of diagnosis (60%) 4.
- The primary lesion is usually located in the pancreas, but can also be found in the duodenum or retroperitoneum 2.
- The diagnosis of VIPoma is based on clinical features, laboratory analysis of blood and stool, radiological imaging, and immunohistochemical findings 2, 3, 4, 5.
Treatment of VIPoma
- The primary treatment for VIPoma includes fluid replacement, electrolyte balance correction, pharmacological treatment with somatostatin analogs, surgical resection, and chemotherapy 2, 3, 4, 5.
- Complete surgical resection is the only potentially curative treatment, but when the neoplasia cannot be excised completely, surgical debulking may provide palliative benefit 4.
- Somatostatin analogs, such as octreotide, can inhibit the release of VIP and provide symptom relief 6.