Insulinoma. The value of intraoperative ultrasonography.

After establishing the diagnosis of an insulinoma, most surgeons prefer preoperative localization. Selective arteriography has long remained the gold standard for this purpose, but its use has been met with variable success. Despite various attempts at localization, insulinomas remain undetected in 10% to 20% of patients, and there may be a postoperative complication rate of at least 10% to 25%. To review the results and surgical implications of current localization techniques, 36 adult patients who were surgically treated for insulinomas at the Mayo Clinic, Rochester, Minn, from July 1982 through June 1987 were studied. The sensitivities of tumor localization using arteriography, computed tomography, and preoperative and intraoperative ultrasonography were 53%, 36%, 59%, and 90%, respectively. A subset of 29 patients underwent intraoperative ultrasonography, and all of these patients' insulinomas were identified with a combination of this technique and intraoperative palpation, with nonpalpable tumors being imaged in four patients. In 18 patients (62%), information obtained from the images appeared to influence the surgical management. While there is no substitute for exploration by an experienced surgeon, exploration appears to be enhanced by the addition of intraoperative ultrasonography, particularly during reoperation.