The target calyx axis was used as the ultrasonic-guided marker to achieve percutaneous renal puncture. Schematic diagram in the left presents the needle entering the collecting system from the axis of the calyx along the ultrasonic guide line. Schematic diagram in the right displays the axis of the desired calyx on an ultrasonic image, and the ultrasonic guide line can assist the puncture needle to enter the collecting system from the axis of the desired calyx.