Insulinoma and islet cell hyperplasia: value of the calcium intraarterial stimulation test when findings of other preoperative studies are negative.

PURPOSE: To evaluate the efficacy of the intraarterial calcium test in localizing sources of hyperinsulinism that remain undetectable at preoperative morphologic studies.

MATERIALS AND METHODS: Twenty-four patients with clinically proved endogenous hyperinsulinism due to tumorous insulin production were prospectively enrolled. They underwent ultrasound (US), computed tomography, magnetic resonance imaging, endoscopic US, abdominal arteriography, and a calcium test, in which insulin concentrations were measured in hepatic venous blood after selective intraarterial calcium stimulation. The results of the calcium test in seven patients (five women, two men; age range, 30-66 years; mean age, 47 years) with negative findings of morphologic studies are described.

RESULTS: Six solitary insulinomas (mean diameter, 0.73 cm) and one nodular hyperplasia were diagnosed after surgery. In all seven cases, calcium test findings allowed accurate localization of the pathologic source of insulin secretion. In three of these seven cases, results of arterial calcium stimulation with hepatic venous sampling (ASVS) affected intraoperative management. An increase in insulin concentration after stimulation in the hepatic artery was not observed, making hepatic metastases unlikely.

CONCLUSION: ASVS, which is procedurally simpler than transhepatic pancreatic venous sampling, is effective for localizing sources of hyperinsulinism not detected with preoperative morphologic studies.