Islet-cell tumors: detection of small lesions with computed tomography and ultrasound.

Fifteen patients with a total of 16 islet-cell tumors 7-20 mm in diameter (average, 12 mm) were examined preoperatively by computed tomography (CT) and ultrasound. Seven out of 16 tumors were detected by CT and 9 out of 15 by ultrasound. Marked contrast enhancement was seen on dynamic CT scans following a bolus injection, while a circumscribed, hypoechoic mass was seen on ultrasound. Tumors of the tail of the pancreas and those outside the pancreas were difficult to detect. Ultrasound is recommended as the initial step for locating islet-cell tumors, followed by CT; angiography and transhepatic venous sampling should be restricted to tumors which are not detectable by other methods. Intraoperative ultrasound was successful in 3 patients and may facilitate the operative search.