Abstract
A case of insulinoma in which intraoperative monitoring of plasma immunoreactive insulin (IRI) level was useful as an index for excision of the tumor was experienced. This case had a typical insulinoma satisfying Whipple's three signs. Preoperative abdominal ultrasonography, CT, and angiography revealed a tumor in the head of the pancreas. A bisferious atypical pattern was shown by 75 g OGTT. The tumor was yellowish brown, solid, 9×9 mm in size, and 1.1 g in weight. Insulin staining was positive. Histologically it was diagnosed as insulinoma. Plasma IRI level remarkably decreased immediately after the tumor was excised, and the decreased level was maintained to the end of the operation. No hyperglycemic rebound after the excision of the tumor was noted. As an index of tumor excision, intraopertive monitoring of plasma IRI level was useful. On the 3rd month after surgery the fasting blood sugar and plasma IRI were as stable as around 90 mg/dl and 10 uU/ml or less, respectively. Preoperative pancreatic polypeptide was as high as 815 pg/ml, but, it rapidly decreased after the operation and was in normal range (114 pg/ml) on the 3rd month postoperatively. The significance as a marker for insulinoma was confirmed.
