Intraarterial calcium stimulation and intraoperative ultrasonography in the localization and resection of insulinomas

Background. Standard imaging studies (computed tomography, magnetic resonance imaging, somatostatin receptor scintigraphy, ultrasonography, and angiography) correctly localize insulinomas in less than 50 % of patients and provide no information about the feasibility of enucleation based on proximity of tumor to pancreatic duct. We reviewed our experience with intraarterial calcium stimulation (Ca-Stim) and intraoperative ultrasonography (IOUS) to localize and guide management of insulinomas. Methods. Thirty-six patients (14 men, 22 women, median age 44 years) with insulinomas were treated between August 1989 and June 1996. Preoperative imaging studies were obtained. Patients underwent abdominal exploration with IOUS. Fourteen were evaluated by a surgeon blinded to preoperative imaging results. Results. Tumors (4 to 50 mm) were resected by enucleation (67 %) or partial pancreatectomy (33 %); all were cured. Sensitivities of computed tomography, magnetic resonance imaging, somatostatin receptor scintigraphy, ultrasonography, angiography, and Ca-Stim in localizing insulinomas were 24 %, 45 %, 17%, 13%, 43%, and 94%, respectively. Tumors were identified by blinded surgical exploration with IOUS in 12 of 14 patients (86%). Conclusions. All insulinomas were identified before operation; however, sensitivity of individual noninvasive tests was low (less than 50%). In contrast, Ca-Stim was correct in 94% of cases, thus allowing a focused pancreatic exploration and obviating use of blind distal pancreatectomy. IOUS can then be used to guide safe enucleation.