Usefulness of selective arterial calcium injection test and secretin test in patients with insulinoma

Preoperatively, it is sometimes very difficult to localize pancreatic endocrine tumors by conventional imaging techniques. Insulinoma is often solitary and benign, but 10% of insulinomas are multiple and malignant. To perform a curative resection of insulinomas, it is important not to leave any tumor postoperatively. In patients with gastrinomas, the selective arterial secretin injection test has been demonstrated to be useful for the curative resection of gastrinomas, since this test tells us whether there is a gastrinoma in the area of interest. The principle of this test is based on the observation that gastrinomas promptly release gastrin when stimulated by secretin. Following a principle analogous to that underlying the secretin test, we have used calcium solution as a stimulant for insulinoma. This selective arterial calcium injection (SACI) test has been used in Kyoto and in National Institute in Health, Bethesda, USA, NIH since 1990. In three patients with insulinoma, curative resection was performed successfully, based on localization by the SACI test. For the differential diagnosis of insulinoma and B cell hyperplasia, we used the intravenous secretin test in 14 patients who had had episodes of hypoglycemia; the test was useful, showing 75% sensitivity and 100% specificity.