LOCALIZATION OF INSULINOMAS TO REGIONS OF THE PANCREAS BY INTRAARTERIAL STIMULATION WITH CALCIUM

Objective: To determine the sensitivity of calcium injected into pancr eatic arteries in localizing insulin-secreting tumors to regions of th e pancreas. Design and Patients: To stimulate the release of insulin, 25 patients with surgically proven insulinomas (average diameter, 15 m m) had calcium gluconate (0.025 mEq Ca++/kg body weight) injected befo re surgery into the arteries supplying the pancreatic head (gastroduod enal and superior mesenteric arteries) and the body and tail (splenic artery) of the pancreas. Setting: Tertiary referral hospital. Measurem ents: Insulin levels were measured in samples taken from the right and left hepatic veins before and 30, 60, and 120 seconds after calcium i njection. A twofold increase in insulin level in the sample taken from the right hepatic vein 30 or 60 seconds after injection localized the insulinoma to the segment of the pancreas supplied by the selectively injected artery. Localization done using calcium stimulation was comp ared with localization done using transcutaneous ultrasonography (n = 22), computed tomography (n = 23), magnetic resonance imaging (n = 21) , arteriography (n = 25), and portal venous sampling (n = 9) Results: Calcium stimulation localized 22 of 25 insulinomas (sensitivity, 88% [ 95% CI, 68% to 97%]) to the correct region of the pancreas. The sensit ivities of the other imaging methods were 9% for ultrasonography (CI, 1% to 23%), 17% for computed tomography (CI, 5% to 39%), 43% for magne tic resonance imaging (CI, 22% to 66%), 36% for arteriography (CI, 18% to 57%), and 67% for portal venous sampling (CI, 30% to 93%). Calcium stimulation added only a few minutes to the time needed for pancreati c arteriography and caused no morbid conditions. Conclusion: Intra-art erial calcium stimulation with right hepatic vein sampling for insulin gradients is the most sensitive preoperative test for localizing insu linomas.