BACKGROUND: Fasting hypoglycemia with neuroglycopenic symptoms corrected by administration of glucose are the hallmarks for the diagnosis of insulinoma. Surgical resection is the treatment of choice for insulinomas, but localization of these lesions can be challenging. Blind distal pancreatectomy has been advocated for occult insulinomas not detected on imaging studies or during abdominal exploration. With the advent of newer localization techniques, we challenge the wisdom of this approach. STUDY DESIGN: The records of patients (multiple endocrine neoplasia excluded) with pathologically proved insulinoma who were screened at our institution or referred to us after a failed blind distal pancreatectomy were reviewed. All records included patient history and results of physical examination and routine blood and urine tests. The diagnosis of insulinoma was confirmed during a supervised fast. Patients with biochemically proved insulinoma underwent localization studies and operation. Studies included CT scans, MRI, transabdominal ultrasound, intraoperative ultrasonography, angiography (more recently, Ca++-stimulated arteriography), and venous sampling. RESULTS: From 1970 to 2000, 99 patients (34 men, 65 women; mean age 43 years) underwent operation. All patients with benign tumors (92) were cured after operation. Seventeen patients were referred to the NIH after a failed blind distal pancreatectomy. Of these, 5 were diagnosed as having factitious hypoglycemia. In the other 12 patients a tumor was localized in the pancreatic head. Two patients incorrectly diagnosed with nesidioblastosis after initial surgery were subsequently cured by resection of an insulinoma. CONCLUSIONS: The use of preoperative imaging studies, most notably Ca++-stimulated arteriography, and intraoperative ultrasonography permits detection of virtually all insulinomas, including reoperated cases. When a tumor is not detected, the procedure should be terminated and the patient referred to a center capable of performing advanced preoperative and intraoperative localization techniques. With the preoperative and intraoperative imaging strategies currently available, the use of blind distal pancreatectomy for occult insulinoma should be abolished.
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