Intraarterial calcium stimulation test for detection of insulinomas

Occult insulinomas are adenomas not visualized by routine preoperative imaging studies, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and arteriography. Reliance for detecting occult insulinomas has been placed on portal venous sampling (PVS), a sensitive (> 75%) but invasive procedure that requires considerable experience to enable sampling of small veins about the pancreatic head. For the past 2 years we have attempted to localize insulinomas by stimulating the release of insulin with a selective intraarterial injection of calcium gluconate and sampling for insulin gradients in the hepatic veins. This study replaces PVS by indicating the region of the pancreas within which the tumor lies, although, like PVS, it does not directly visualize the tumor. Our experience in 9 patients with surgically proved insulinomas is reviewed, comparing the results with PVS as well as with US, CT, MRI, and arteriography.