Selective venous sampling for gastrin to localize gastrinomas. A prospective assessment.

In 27 consecutive patients with Zollinger-Ellison syndrome, we prospectively evaluated the ability of selective venous sampling for gastrin to localize gastrinomas, then compared the results with those from imaging studies and with findings at surgery. All patients had a gastrin gradient, but in only 20 patients was it significant. Neither the magnitude of the gastrin gradient nor its presence or absence correlated with the frequency with which gastrinoma was found at surgery. A gastrinoma was found at surgery in 15 patients, of whom 12 had positive imaging studies, 11 had a significant gastrin gradient, 14 had both tests positive, and 1 had both tests negative. A gastrinoma was not found at surgery in 12 patients, of whom 8 had a significant gradient and none had a positive imaging study. Gastrin sampling has equal sensitivity with imaging studies in localizing gastrinoma, but imaging studies have higher positive and negative predictive values and higher specificity. Thus, selective venous sampling for gastrin is much less useful in localizing gastrinoma than has been suggested and should not be routinely done preoperatively in patients with Zollinger-Ellison syndrome.