Intraoperative ultrasonographic localization of islet cell tumors. A prospective comparison to palpation.

The purpose of the present study was to evaluate prospectively the value of intraoperative ultrasound scanning (IOUS) in localizing islet cell tumors by comparing results of IOUS to those of palpation during 44 consecutive laparotomies for gastrinoma (36) or insulinoma (8). All patients had preoperative radiographic imaging studies and selective venous sampling for hormones, which guided the subsequent laparotomy. Any suspicious finding by palpation and/or IOUS was resected. Pathologic evidence of islet cell neoplasm served as the reference standard. Five patients were excluded from analysis because neither palpation nor IOUS had suspicious findings and no islet cell tumor was found. Seven pancreatic insulinomas were found in seven patients. IOUS was as sensitive as palpation at localizing insulinomas. Twenty-three pancreatic gastrinomas were found in 19 patients. IOUS was equal to palpation in the ability to localize gastrinomas. Gastrinomas that were successfully imaged by IOUS were significantly larger than gastrinomas that were not imaged. Twelve extrapancreatic gastrinomas were found in nine patients, and palpation was more sensitive than IOUS at localizing these small duodenal wall tumors. Five patients (11%) had their surgical management changed by IOUS. Two patients had pancreatic tumors (one gastrinoma and insulinoma) enucleated that would not have been found without IOUS, and three patients had resections of pathologically proven malignant islet cell tumors based on sonographic findings. All five patients were cured with short follow-up. The present results demonstrate that palpation and IOUS are complementary because IOUS can image tumors that are not palpable and IOUS can provide additional information concerning malignant potential not detected by palpation.