Intraoperative ultrasound and preoperative localization detects all occultinsulinomas

Hypothesis: Preoperative invasive localization procedures with intraoperati ve ultrasound (IOUS) can result in successful surgical treatment of occult insulinomas when noninvasive imaging study results are equivocal or negativ e. Design: Prospective study. Setting: Tertiary care university hospital. Patients: Thirty-seven consecutive patients with a biochemical diagnosis of insulinoma without multiple endocrine neoplasia (MEN). Intervention: All patients underwent portal venous sampling (PVS) (n = 22) or calcium angiogram (n = 15) followed by surgery with palpation and IOUS ( n=37). Main Outcome Measure: Portal venous sampling, calcium angiogram, palpation, and IOUS were compared for accurate localization of insulinoma. Results: All patients were cured of hypoglycemia after surgery. Portal veno us sampling correctly localized tumors in 17 (77%) of 22 patients. Calcium angiogram was correct in 13 (87%) of 15 patients. Palliation identified 24 (65%) of 37 tumors, and IOUS found 35 (95%) of 37 tumors. The 2 tumors miss ed by IOUS were located in the tail of the pancreas and were resected based on regional localization alone, Conclusions: Intraoperative ultrasound is the single best localization stud y, but it will miss some tumors that regional localization can identify. Co mbining both modalities allowed surgical cure of all insulinomas in our stu dy. Therefore, we recommend both IOUS and regional localization for insulin oma when preoperative imaging studies are equivocal.