In nine patients who had insulinomas, celiac arteriography was found to be useful in locating the tumor, and serial measures of the blood glucose level proved helpful in monitoring the patient during surgery; in each patient, blood glucose levels rose after the tumor was removed. An increase in blood glucose concentration during the first hour after removal of a portion of the pancreas, or in some instances during the second succeeding half hour, was consistent with the assumption that other insulinomas were not left behind.
Ferris DO, Molnar GD, Schnelle N, Jones JD, Moffitt EA. Recent Advances in Management of Functioning Islet Cell Tumor. Arch Surg. 1972;104(4):443–446. doi:10.1001/archsurg.1972.04180040057010