A method of removing/retrieving calculus in a ureteral lumen involves moving a ureteral plug part along the ureter lumen to position the ureteral plug part between the calculus and the kidney. The method additionally includes occluding the ureteral lumen at a location at which the ureteral plug part is located, and introducing fluid into the ureter lumen at a point between the location of the occlusion and the calculus so that the fluid washes the calculus toward the bladder. Another aspect involves a method in which an drainage tube is positioned in the ureteral lumen so that a ureteral plug part and an irrigation port are positioned distally of the calculus while an operation part of the drainage tube is positioned proximally of the calculus. The method includes occluding the ureteral lumen, washing the ureteral lumen, and releasing the occlusion and uncoupling the operation part from the ureteral plug.