Intra-arterial calcium provocation for the preoperative diagnosis of the location of an occult insulinoma

Abstract

Blood-sugar levels below 40 mg/dl were measured during syncope in two female patients (aged 59 and 73 years). Suspected organic hyperinsulinism was confirmed by a fasting test. Ultrasound examination and computed tomography failed to demonstrate an insulinoma. Coeliacomesentericography was then undertaken together with a selective intra-arterial calcium provocation test of the pancreas (0.4 or 0.5 mmol calcium in physiological saline was injected into the pancreas-supplying arteries--proximal and distal splenic, superior mesenteric and gastroduodenal). The insulin level was determined in simultaneously obtained hepatic venous blood. In case 1, the insulin level rose tenfold after calcium injection into the proximal splenic artery, indicating a process in the body of the pancreas. In case 2, a steep rise in insulin occurred after injection into the truncus coeliacus and the proximal and distal splenic artery, suggesting an insulinoma in the tail of the pancreas. The site of the insulinoma was confirmed in both cases at surgery. The adenoma was enucleated in case 1, removed by partial resection of the tail of the pancreas in case 2.--These observations show that occult insulinomas can be localized preoperatively by intraarterial calcium injection with measurement of insulin concentration in simultaneously obtained hepatic venous blood.