gastrointestinal disorders
Vipoma
Diagnosis of Vipoma
Confirmation of secretory diarrhea Serum vasoactive intestinal peptide (VIP) levels Endoscopic ultrasonography, positron emission tomography (PET), or scintigraphy can localize Diagnosis of vipoma requires demonstration of secretory diarrhea (stool osmolality is close to plasma osmolality, and twice the sum of sodium and potassium concentration in the stool accounts for all measured stool osmolality). Other causes of secretory diarrhea and, in particular, laxative abuse must be excluded (see Testing ). In such patients, serum VIP levels should be measured (ideally during a bout of diarrhea). Markedly elevated levels establish the diagnosis, but mild elevations may occur with Patients with elevated VIP levels should have tumor localization studies, such as endoscopic ultrasonography, PET, andoctreotidescintigraphy or arteriography to localize metastases. 50% of patients. Hypercalcemia occurs in 50% of patients. 