- Brush: the RX-cytology brush (M00545000, Boston Scientific Corp., Natick, Mass.) will be passed as a unit within its 8 French sheath, over the guidewire through the stricture. Previous stricture dilation will be left at the discretion of the endoscopist. The brush/sheath will be withdrawn immediately below the stricture, the brush will be moved forth and back within the strictured segment at least 10 times. The brush will then be pulled into the catheter, still located immediately below the stricture, and the unit brush/catheter will be removed. A X-ray will be taken with the top of the brush inside the stricture, and the X-ray will be kept in a dedicated file, as well as a X-ray with the stricture opacified with contrast medium. Specimens obtained with the brush will be smeared on glass slides and fixed in 95% ethanol immediately after collection, in the ERCP suite. Immediately after, the brush will be agitated in 10 ml of saline placed in a vial. Finally, the brush segment will be cut from the supportive wire and placed into a container with CytoLytt solution (Cytyc, Crawley, United Kingdom).