Introduction: Non-invasive imaging modalities are often unable to localize insulinomas. Localization through calcium stimulation test is often dependent on expertise of the operator.

Aim: To assess the accuracy of calcium stimulation in diagnosis of cause of hypoglycemia at a tertiary referral centre.

Method: This is a retrospective analysis of a single centre experience in Newcastle, Australia from 2001 to 2015.

Results: 14 consecutive patients, 8 females and 6 males with mean age 33.5 years (range 25-42) were investigated for insulinoma over the past 14 years at John Hunter Hospital, Newcastle. Calcium stimulation test was performed on all patients by injecting calcium gluconate 0.025 mEq/kg directly into the arteries supplying the pancreas and liver. Samples were collected from the hepatic vein at -120,0, 30, 60,90, 120, 180 seconds. The results of the study were compared with the intraoperative and histological findings in 9 patients. The findings were also compared with other imaging modalities.

Preliminary analysis showed that 2/14 had MEN 1 syndrome. 9/14 patients had insulinoma, 1/14 factitious disorder, 1/15 congenital hyperinsulinsm, 2/14 had post gastrectomy hyperinsulinemia. Calcium stimulation test identified insulinoma correctly in all 9 cases. It was truly negative in 3 cases (factious, congenital hyperinsulinism, post gastrectomy hyperinsulinemia). It was falsely positive in 1 case of post gastrectomy hyperinsulinemia.

Of these 9 cases of insulinoma only 3 were identified on CT scan and 1 on MRI. Indium octreotide was done in 3 cases and was falsely negative in all 3. Gallium dotatate was done in 3 cases and was true positive in 1 case and truly negative in in 2 cases.

Conclusions: Calcium stimulation test remains the investigation of choice for localizing insulinoma. Expertise at our centre was comparable to other centres in the world. Of all the other non-invasive imaging modalities, gallium dotatate scan was the best performing.