Transhepatic portal sampling for preoperative localization of insulinomas.

The data of 72 patients with pancreatic insulinomas were analyzed. Twenty-one were obtained from personal experience and 51 from a review of the literature. In all instances, detailed information about insulin levels in the portal tree as obtained by means of a transhepatic portal sampling (THPS) and localization of the tumor as found during the surgical procedure was available. Five different criteria were compared for defining the peak insulin concentrations regarded as indicative of tumor localization: 1, peak above 500 milliunits per liter; 2, peak above 200 milliunits per liter; 3, peak 2.5 times higher than the lowest portal value; 4, peak 2.3 time higher than the distal mesenteric value, and 5, peak higher than mean portal concentration plus or minus 2 standard deviation. Criterion 5, associated with sample numbers larger than 15 and catheterization of the cephalic veins, provided the best results for obtaining valuable information from THPS.