Removal of a double-J tube for kidney stones is usually done with a cystoscope, but if the stent tube enters the ureter a ureteroscope is needed. Double-J tubes are used to contact acute hydronephrosis caused by stones or to prevent hydronephrosis caused by ureteral stenosis in postoperative patients when placed in the ureter after surgery for renal ureteral stones. Normally, the double-J tube will remain partially outside the ureter after it is placed into the ureter, so the free end of the double-J tube can be clearly detected using cystoscopy, and then the double-J tube can be removed with the aid of an instrument. However, if the patient’s double J-tube moves and enters the ureter after placement, it can be removed with the aid of a ureteroscope.