A flexible elongate device having a distally mounted occluder for collecting particulate debris in a body lumen. The occluder containing a fixed amount of fluid is reversibly expandable by push-pull actuation from a contracted configuration to a deployed configuration wherein the occluder is expanded into sealing engagement with the wall of the body lumen. The occluder has a distal end axially secured to an elongate inner member and a proximal end attached to a distal end of an outer tubular member. The occluder has an impermeable occluder casing for containing the occluder fluid. The elongate inner member is slidable within the outer tubular member such that relative longitudinal movement between the elongate inner member and outer tubular member changes the length of the occluder and thus redistributes the occluder fluid within the occluder casing to transform the occluder between its contracted and deployed configurations.