[Diagnostic localization of insulinoma. Experiences with 25 patients with solitary tumors]

The most effective way to localize the mostly small ( < 2 cm), benign and solitary insulinomas is still under discussion. Especially the evaluation of the different preoperative localization methods is not clarified. The aim of our study was to support the ongoing discussion in that matter.

In total 25 patients have been included in our study since 1987. All showed sporadic insulinomas and underwent surgery. The following preoperative localization methods had been used: ultrasonography (US): 25 patients, computed tomography (CT): 23 patients, somatostatin receptor scintigraphy (SRS): four patients since 1990, angiography: six patients, endosonography (ES): five patients since 1995, selective portal venous sampling (PVS): two patients, magnetic resonance imaging (MRI): four patients since 1993. All 25 patients underwent a bidigital palpation in combination with intraoperative ultrasonography (IOUS). Four of the 25 patients were reoperated and had a prior unsuccessful operation elsewhere.

Preoperatively 19 of 25 insulinomas were localized (76%). The following sensitivity rates had been found: ultrasonography: 56%, computed tomography: 43%, endosonography: 100%, angiography: 66%, magnetic resonance imaging: 25%, selective portal venous sampling: 100%, somatostatin receptor scintigraphy: 0%. All 25 insulinomas were detected during operation, 100% by palpation in combination with intraoperative ultrasonography and 92% by palpation on its own.

After an insulinoma is biochemically proven and after exclusion of a malignant metastasizing tumor by ultrasonography, all patients should be operated on. Intraoperative ultrasonography should be performed in any case. As other preoperative localization methods did not prove a convincing cost-utility-relation, one should not consider the usage of these methods before the initial operations. Before re-operations one should consider the use of costly pre-operative methods to localize insulinomas. Here endosonography and selective portal venous sampling are recommended as the first procedures of choice.