Prospective study of the ability of computed axial tomography to localize gastrinomas in patients with Zollinger-Ellison syndrome.

The ability of routine computed tomography (CT) performed with oral and intravenous contrast to localize gastrinomas in 61 consecutive patients with Zollinger-Ellison syndrome was evaluated prospectively. The results of CT scanning were subsequently evaluated in all patients by either surgery, autopsy, or percutaneous biopsy. Thirteen of 14 patients with CT scans positive for hepatic metastases and 5 of 13 patients with CT scans negative for hepatic metastases were found to have gastrinoma in the liver. For gastrinoma metastatic to the liver, CT scanning had a specificity of 98%, a sensitivity of 72%, a positive predictive value of 93%, and a negative predictive value of 90%. Twenty-two of 23 patients with positive extrahepatic CT scans and 15 of 33 patients with negative extrahepatic CT scans were found to have extrahepatic gastrinomas. For extrahepatic gastrinoma, CT scanning had a specificity of 95%, a sensitivity of 59%, a positive predictive value of 96%, and a negative predictive value of 54%. The ability of CT scan to detect gastrinomas both in the liver and extrahepatically was directly related to tumor size, detecting 0% of tumors less than 1 cm and 83%-95% of tumors greater than 3 cm. The location of the extrahepatic gastrinoma was also an important determinant in that approximately 80% of pancreatic gastrinomas but only 35% of extrapancreatic gastrinomas were detected. The present results indicate that because of its convenience and accuracy, CT scanning with oral and intravenous contrast material should be the initial procedure to evaluate the extent of gastrinoma. A positive CT scan is almost always correct; therefore, a CT scan detecting metastatic gastrinoma to the liver would avoid unnecessary surgery and, if positive for extrahepatic gastrinoma, would assist the surgeon in finding the gastrinoma. A negative CT is less reliable; therefore, patients should undergo other localizing studies before exploratory laparotomy.