A method of removing/retrieving calculus in a renal pelvis includes moving a renal cover part along a ureter toward the renal pelvis, introducing the renal cover part into the renal pelvis, positioning the renal cover part in the renal pelvis so that the renal cover part covers one part of the renal pelvis, while an other part of the renal pelvis is not covered by the renal cover part, introducing fluid into the other part of the renal pelvis, while the one part of the renal pelvis is covered by the renal cover part, to cause the calculus in the other part of the renal pelvis to be washed-out of the renal pelvis, and moving the renal cover part out of the renal pelvis and into the ureter.
