A medical retrieval device, and related method, for removing material, such as calculi, from a patient's body. In one embodiment, the device includes a handle, a sheath, and a retrieval assembly located at the distal end of the retrieval device. The retrieval assembly includes a plurality of legs, each of which includes a lumen for receiving fluid. The legs are made of an expandable material that will allow the legs to inflate when the lumen receives a fluid. In another embodiment, the device includes a core element wound to form a helical coil. The helical coil has a lumen for receiving a fluid. The core element is made of an expandable material that allows it to inflate when the lumen within the helical coil receives a fluid.