Intraoperative ultrasonic localization of endocrine tumors of the pancreas.

Small endocrine tumors of the pancreas can be located before operation by computerized tomography, ultrasonography, angiography, or percutaneous transhepatic venous sampling for hormone assay; to these may eventually be added nuclear magnetic resonance studies. Precise preoperative localization of insulinomas is possible in 80% to 90% of the cases if a stepwise approach combining these methods is used. In as many as 10% of the patients with organic hyperinsulinism and as many as 50% of the patients with Zollinger-Ellison syndrome problems are encountered during the operation because either the tumor cannot be palpated or there are multiple tumors. Only 25% of the multiple tumors are known by angiography before operation. Forty percent of the tumors have a diameter of less than 1 cm. Numerous methods have been reported for intraoperative localization of endocrine pancreatic neoplasms.