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When should neuroendocrine tumors be suspected as a cause of chronic secretory diarrhea?
- Neuroendocrine tumors are uncommon causes of chronic secretory diarrhea. For example, one VIPoma might be expected per 10 million people per year.
- The below table lists these tumors and their markers. Because of the rarity of these tumors as a cause for chronic diarrhea, other causes of secretory diarrhea should be considered first.
- If tumor is visualized by CT scan or if systemic symptoms (e.g., flushing) are present, evaluation for neuroendocrine tumors may have a better yield. Blanket testing for tumor-associated peptides is likely to yield many more false-positives than true-positives and therefore can be very misleading.
Neuroendocrine Tumors Causing Chronic Diarrhea and Their Markers
| Typical Symptoms | Tumor | Mediator and Tumor Marker |
|---|---|---|
| Gastrinoma | Zöllinger-Ellison syndrome: pancreatic or duodenal tumor, peptic ulcer, steatorrhea, diarrhea | Gastrin |
| VIPoma | Verner-Morrison syndrome: watery diarrhea, hypokalemia, achlorhydria, flushing | Vasoactive intestinal polypeptide |
| Medullary thyroid carcinoma | Thyroid mass, hypermotility | Calcitonin, prostaglandins |
| Pheochromocytoma | Adrenal mass, hypertension | Vasoactive intestinal polypeptide, norepinephrine, epinephrine |
| Carcinoid | Flushing, wheezing, right-sided cardiac valvular disease | Serotonin, kinins |
| Somatostatinoma | Nonketotic diabetes mellitus, steatorrhea, diabetes, gallstones | Somatostatin |
| Glucagonoma | Skin rash (migratory necrotizing erythema), mild diabetes | Glucagon |
| Mastocytosis | Flushing, dermatographism, nausea, vomiting, abdominal pain | Histamine |
VIPoma, Vasoactive intestinal polypeptide tumor.
