Evaluation of preoperative and intraoperative arterial stimulation and venous sampling for diagnosis and surgical resection of insulinoma

Background. The precise intraoperative localization of insulinoma is essent ial for successful surgical treatment. In addition to various imaging modal ities developed recently, arterial stimulation and venous sampling (AST'S) has also been used for tl,nor localization. Methods. Preoperative and intraoperative ASVS procedures were performed In 6 patients with insulinoma. Intraoperative ASVS was performed before and af ter tumor resection. Immunoreactive insulin (IRI) concentrations and the IR I ratio (IRI concentration at each time interval after calcium injection/ba seline IRI concentration) were determined by rite conventional or a quick I RT method. Results. The site of the tumor was identified preoperatively in all patient s. The peak of the IRI ratio varied widely, but setting the cutoff value at 3.0 clearly differentiated peak IRA ratios in feeding arteries from those of nonfeeding arteries. Intraoperative ASVS showed a similar elevation of I RI levels, but the elevation disappeared after tumor resection in all but I patient. In 2 patients, resection of the tumor was confirmed during surger y by measuring IRI levels by the quick IRI method. Conclusions, A combination of ASVS and conventional imaging modalities is u seful for precise localization of insulinoma. Resection of the tumor can be confirmed intraoperatively by comparing IRT levels associated with preoper ative and postresective ASVS.