Stones can cause bleeding in urine. The surface of stones are mostly irregular and have sharp edges, which can cause bleeding by stabbing the mucosa of the urinary tract during stone activity, presenting as flesh-eye hematuria, such as small stones discharged through the urethra, manifesting as transient stabbing pain in the urethra, followed by blood flowing out of the urethra. Bladder stones constantly changing position in the bladder or acute obstruction of ureteral stones can cause bleeding by injuring the mucosa of the urinary tract and presenting as flesh-eye hematuria. Bleeding from damage to the mucosa of the urinary tract can also be incidental to stone treatment, such as bleeding in urine after extracorporeal lithotripsy, holmium laser lithotripsy under ureteroscopy, percutaneous nephrolithotripsy, and cystoscopic removal of bladder stones.