A method involves introducing a gathering part into a lumen in an ureteral access sheath in which is located calculus, wherein at least a part of the ureteral access sheath is located in an ureter in a living body. The gathering part is moved along the lumen in the ureteral access sheath in a forward direction toward the calculus, and then movement of the gathering part in the forward direction is stopped to position the gathering part adjacent the calculus so that the calculus is positioned between the distal end of the ureteral access sheath and the gathering part. The gathering part is expanded while the gathering part is positioned adjacent the calculus, and the calculus is then introduced into the gathering part.