LIMITATIONS OF INTRADUCTAL ULTRASONOGRAPHY IN DIFFERENTIATING BETWEENBILE-DUCT CANCER IN STAGE T1 AND STAGE T2 - IN-VITRO AND IN-VIVO STUDIES

Background and Study Aims: We investigated whether intraductal ultraso nography (IDUS) could distinguish between stage T1 and T2 bile duct ca ncer. Materials and Methods: In-vitro study. Resected bile duct specim ens (n = 8) were immersed in a water tank and were pierced with straig ht pins to clarify the normal layer structure. Ultrasonosgraphic image s (20MHz) of the positions of pin echoes were compared to the position s of pin holes as seen on histologic analysis of the specimens. In-viv o study. A thin-caliber high-frequency (6Fr, 20MHz) ultrasonic probe w as inserted into the bile duct via a transhepatic route or a transpapi llary route in 26 patients with bile duct cancer who underwent surgica l resection. Results: In-vitro study. The inner hypoechoic layer on th e IDUS image corresponded not only to the fibromuscular layer but also to a part of fibrous layer of the perimuscular loose connective tissu e on histologic analysis, especially in the cases with moderate to sev ere bile duct wall fibrosis. The outer hyperechoic layer corresponded to the subserosal fat tissue. In-vivo study. In four of six patients w ith tumor limited to the inside hypoechoic layer on IDUS images, the h istologic findings showed tumor invasion to the fibrous layer of the p erimuscular loose connective tissue. Due to this limitation, accuracy of IDUS in T-staging was only 20/26 (77%). Conclusions: IDUS cannot re liably distinguish bile duct cancer in stage T1 from that in stage Ti.