An instrument particularly useful for locating and removing ureteral calculi and other occlusive objects from body passages. The instrument includes a flexible tube or sheath which slidably receives a tightly-twisted multi-stranded cable of a length greater than that of the tube, the cable having an integral cage portion at its distal end. That cage portion, which is normally collapsed and concealed within the distal end of the tube, may be extended beyond the tube to assume an expanded helical pear-shaped configuration for ensnaring and withdrawing ureteral stones and other passage-occluding bodies. The tightly wound strands of the cable are arranged in a circumferential pattern about an axial lumen which in one embodiment is useful for fluid drainage and injection and which in other embodiments accommodates conductors for transmitting light, images, and/or ultrasonic energy. The sheath or outer tube of the instrument is transparent, thereby permitting visual inspection of the spirally-wound cable slidably disposed therein. Suitable markings on the cable, visible through the transparent wall of the sheath, indicate the extent of insertion of the instrument during an operative procedure. The instrument also includes a handle for extending and retracting the cage, and suitable means for generating and transmitting light and ultrasonic waves.