Intra-operative blood glucose and serum insulin concentrations in the surgical management of insulinoma.

The surgical management of insulinoma is frequently complicated by difficulty in pre- and intra-operative localization of the tumour. An early and reliable post-operative indicator of successful surgery would therefore be useful in the management of this condition. In a prospective, controlled study serial measurements of blood glucose and serum insulin concentrations were performed in 5 patients with insulinoma during surgical removal of the tumour. Results were compared with 5 patients, matched for age and body weight, undergoing abdominal surgery for non-malignant disease. Serum insulin (mean +/- s.e.m.) was significantly elevated in the insulinoma patients at the start of surgery (32.1 +/- 3.1 vs 6.1 +/- 2.2 mU/l; P less than 0.01). A significant fall (P less than 0.01) to levels comparable with the control patients (7.5 +/- 1.8 vs 10.0 +/- 3.3 mU/l) occurred following removal of the tumour. We conclude that serial intra-operative measurements of serum insulin concentration are technically simple to perform and provide useful retrospective corroboration of successful surgery in patients with insulinoma.