Preoperative localization and intraoperative glucose monitoring in the management of patients with pancreatic insulinoma.

Whipples triad of hypoglycemic episodes associated with fasting blood sugar levels of less than 50 milligrams per 100 milliliters with relief of the symptoms by the administration of glucose intravenously leads to the clinical diagnosis of insulinoma. This diagnosis can be confirmed in a laboratory by the biochemical measurement of an inappropriate insulin elevation in response to fasting or the infusion of calcium or tolbutamide. Since more than 90 per cent of the tumors are benign, the potential for operative cure is high. Unfortunately, because of multicentricity (12 to 13 per cent) and the frequent small size of the tumor, some series report 15 to 30 per cent of inadequate or failed operations. Preoperative localization, in most centers, has depended upon sonography (positive in one of six patients in our series), computerized tomographic scanning (positive in one of five patients), celiac axis angiography (positive in six of 15 patients) and transportal venous sampling for insulin levels (positive in 11 of 13 patients in our series). We found that the combination of arteriography and transportal sampling has been the most accurate means of precise preoperative localization. In conjunction with preoperative localization, we have used intraoperative monitoring of glucose levels as a guide to the completeness of resection of insulin producing tumors. Sustained elevation of blood glucose levels has confirmed the adequacy of surgical intervention. Failure of the blood sugar level to increase had led to the successful search for additional tumors not identified preoperatively or to further resection. The combination of arteriography, transportal sampling and monitoring of glucose levels has led to the cure of 15 patients operated upon at the Mount Sinai Hospital from 1977 to 1984.