Reasons for treatment of bladder stones include recurring symptoms and risk of urinary tract obstruction. Some stones can be dissolved using dietary modifications and/or medications. Small stones in female dogs may possibly be removed by urohydropropulsion , a nonsurgical procedure. Urohydropropulsion is performed under sedation by filling the bladder with saline through a catheter, holding the dog vertically, and squeezing the bladder to expel the stones through the urethra. Bladder stones can be removed surgically by a cystotomy , opening of the bladder. Stones lodged in the urethra can often be flushed into the bladder and removed, but sometimes a urethrotomy is necessary. In male dogs with recurrent urinary tract obstruction a scrotal urethrostomy creates a permanent opening in the urethra proximal to the area where most stones lodge, behind the os penis . In male cats, stones lodge where the urethra narrows in the penis. Recurrent cases can be treated surgically with a perineal urethrostomy , which removes the penis and creates a new opening for the urethra.