Role of intraoperative insulin monitoring in surgical management of insulinoma

Background and Purpose: Precise localization and surgical excision is the therapeutic strategy for insulinomas. However, it is often difficult to localize the insulinomas, because of their small size. Surgeons may not localize and remove all of them together, particularly in patients with multiple insulinomas. We reviewed our experience to confirm the efficacy of blood glucose and intraoperative immunoreactive insulin (IRI) monitoring for surgical management of insulinomas. Patients and Methods: Thirty-nine patients with insulinoma were surgically treated in our department. Perioperative blood glucose monitoring was performed in 14 patients, intraoperative quick IRI assay of the peripheral blood in 1 patients, and assay of a portal sample in 4 patients by an IMX analyzer. Results: Rebound response of blood glucose to insulinoma removal was not always noted (8/14; 57%). Seven of ten patients showed a decrease of peripheral serum IRI levels within 15 minutes after removal of the insulinoma. The other two patients showed a rebound response of peripheral blood glucose or portal IRI. All the patients who had intraoperative monitoring of peripheral blood and peripheral and portal IRI had no recurrent insulinoma syndrome after surgical removal of their insulinomas. Conclusion: Combined monitoring of peripheral blood glucose and peripheral and portal IRI are helpful in the surgical management of insulinomas, as they can indicate that no insulinoma remains.