Intraductal ultrasonography may localize islet cell tumours negative on endoscopic ultrasound.

Two patients with suspected insulinoma and one patient with a gastrinoma were referred to our hospital for preoperative tumour localization. Conventional imaging methods and even endoscopic ultrasonography did not detect any tumour in the pancreatic parenchyma. During endoscopic retrograde cholangiopan-creatography ultrasound miniprobes with a 2-mm diameter were applied via the biopsy channel of the duodenoscope. After insertion of the ultrasound probe into the pancreatic duct intraductal sonography (IDUS) was able to depict the tumours. The two insulinomas (1.8 x 2 mm and 5 x 8 mm, respectively) could be localized, as could the gastrinoma, which had a diameter of 6 mm. IDUS diagnosis was confirmed by surgery as the tumours were resected. Follow-up showed no evidence of tumour recurrence.