[Studies on the diagnosis of insulinoma]

The results of various tests for the diagnosis and localization of insulinoma in ten patients were reviewed. The diagnostic criteria IRI X 100/(BS-30)greater than 50 and IRI/BS greater than 0.30 in the fast were most reliable in establishing a diagnosis of insulinoma. If a diagnosis of insulinoma is in doubt after several overnight fasts, C-peptide suppression test should be carried out since the test is safe and convenient. As insulin stimulation tests often lead to false-negative results and sometimes cause dangerous levels of hypoglycemia in patients with insulinoma, they are not widely recommended now. However they may be useful, if positive, in some patients with insulinoma who exhibit no abnormality in insulin-glucose ratio or C-peptide suppression test. Percutaneous transhepatic portal catheterization with measurements of radioimmunoreactive insulin concentration, supported by the clear theoretical grounds for interpretation of its results, was the most reliable method for preoperative localization of an insulinoma. Therefore the method, together with pancreatic angiography, should be attempted in all the patients with insulinoma. Insulinoma is an endocrine tumor curable by surgical removal, but there still remain a few unfortunate patients who have brain damages due to severe hypoglycemia or are blindly treated by pancreatectomy. Such cases should be eliminated by the early diagnosis and correct preoperative localization of the tumor.