Localization of Insulinomas

HYPOTHESIS: Intraoperative ultrasonography is more sensitive than preoperative and other intraoperative techniques for localizing insulinoma. DESIGN: Retrospective review. SETTING: A tertiary referral center. PATIENTS: All patients with a biochemical diagnosis of organic hyperinsulinism who were referred to University of California, San Francisco, from 1975 to 1998. METHODS: Sensitivities of the localization techniques for insulinoma were evaluated. RESULTS: The sensitivities of tumor localization with arteriography, computed tomography, preoperative ultrasonography, magnetic resonance imaging, magnetic resonance imaging with gadolinium, transhepatic venous sampling, palpation, and intraoperative ultrasonography were 47%, 24%, 50%, 30%, 40%, 55%, 76%, and 91%, respectively. Nine of the 11 nonpalpable and nonvisible tumors at operation were localized by intraoperative ultrasonography. CONCLUSION: The currently available preoperative localization tests are not reliable enough to be recommended when intraoperative ultrasonography is available.