Endoscopic ultrasonography for the preoperative localization of insulinomas.

Preoperative radiological localization of insulinomas often fails because of the small size of the tumors. We studied retrospectively the value of different procedures in preoperative localization of insulinomas in 18 patients. Radiological assessment included transabdominal ultrasonography, computed tomography, angiography, magnetic resonance imaging, transhepatic venous sampling, and endoscopic ultrasonography (EUS) for the last 11 patients. During surgery, the association of palpation and intraoperative ultrasonography localized 16 solitary tumors and two multiple tumors (mean size, 1.8 +/- 1.1 cm). There insulinomas were found to be malignant. Conventional preoperative methods correctly localized the tumor in seven of 18 cases (38%), whereas the sensitivity of EUS was 10 of 11 cases (90%). Surgical procedures involved eight enucleations, nine distal pancreatectomies, and one total pancreatectomy. Because of its high sensitivity and safety, EUS was found to be the best method for preoperative localization of insulinomas, and we recommend that EUS replace conventional methods for the majority of cases.