[Rebound hyperglycemia and peroperative normalization of insulinemia. Complete excision of insulinoma?]

Clinical usefulness of the hyperglycemic rebound and the normalization of plasma insulin level as intraoperative markers of complete removal of insulinoma was assessed. Surgical removal was curative (no clinical or biological recurrence) in six patients harboring a single adenoma (mean follow-up = 32.2 months). In these patients plasma glucose increased an average of 32 mg/dl 30 minutes after resection, 68 mg/dl after 60 minutes, and 91 mg/dl after 90 minutes. Sensitivity of hyperglycemic rebound (defined as a plasma glucose increment of at least 30 mg/dl after tumor removal) as a marker of complete resection of the insulinoma was 40% at 30 min and 83% at 60 minutes after resection. Preresectional values of plasma immunoreactive insulin were elevated in 3 out of 4 patients with adenoma. All postresectional values were within normal ranges. Two patients operated on because of malignant insulinoma, underwent partial tumor resection; hyperglycemic rebound was also present, and high preresectional insulin values became normal 30 minutes after partial tumor removal. We conclude that information provided by intraoperative monitoring of both plasma glucose and insulin cannot be used as the only markers of complete resection of all insulinomas. Only long term clinical and biological follow-up can guarantee the complete resection of an insulinoma.