Insulinoma is a functional endocrine tumor arising from beta cells of the islets of Langerhans of the pancreas. The tumor is usually a benign, single adenoma and of small size (1-2cm), and is evenly distributed throughout the pancreas. The
symptoms
and
signs are triggered by hypoglycemia. Mechanisms for the production of symptoms are related to the neuroglycopenia causing cerebral dysfunction and the hypoglycemic stimulation of catecholamine release. Complex symptoms originating from these
mechanisms
frequently lead to misdiagnosis as a neurologic or psychiatric disorder and delay proper treatment.
One suspicion of an insulinoma is made, the diagnosis is not complicated. Supervised fast until symptoms develop or for 72 hours bring the blood sugar level down below 50mg/dl with inappropriately high endogenous insulin level. C-peptide and
proinsulin
fraction measured at the termination of the fast confirm the diagnosis.
Preoperative localization of a small insulinoma by ultrasonography, arteriograh or computed tomography is not always successful. Selective portal venous sampling for insulin has been found to be the most accurate method of localization. Careful
exploration of the entire pancreas is very important at laparotomy and intraoperative ultrasonography is essential especially in identifying tumors in the head of the pancreas and in defining the relationship of the tumor to the pancreatic duct.
We report our experience of three patients with insulinoma during the last five year period: one male 23 years old and two females, 38 and 40 years old. Preoperative localization failed in the first patient but in two patients, preoperative
percutaneous
transhepatic portal venous sampling for insulin helped to localize the tumor. A relatively well-demarcated mass lesion was found in each patient, and all three patients were treated with successful outcome. The sizes of the tumors were
1.5×1.0×1.0cm,
2.7×2.2×1.4cm, 1.5×1.0×1.0cm respectively.
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