Abstract: Catheter for use in biliary procedures, including a shaft having a proximal end and a distal end. A guide wire lumen is carried by the shaft extending from a location proximal the distal end of the shaft to a location proximate the distal end of the shaft. A channel extending longitudinally between a first end and a second end is included for accessing the guide wire lumen from a location exterior the catheter shaft located distal the proximal end of the shaft. The catheter may be used in rapid exchange catheter procedures. The channel may be U-shaped, containing the guide wire yet allowing radial removal of the guide wire from the channel. The catheter may also be part of a device including an endoscope exchange sheath for constraining guide wire movement to the catheter channel while inside a large endoscope working channel.