Lions, like other mammals, urinate through their genitals, via a tube that leads from their bladder to the outside world. The urinary system of lions is similar to other cats, in that they use urine both to eliminate waste and communicate via spray-marking.
All mammals have the same basic anatomy for urination. Kidneys filter waste from the blood through a complex system of tubules. A tube called the ureter then transports the fluid that has been processed by the kidneys into the bladder, where it is stored.
In lions and tigers, the urine stored in the bladder also contains odorous fatty substances that aid in marking territory. All species of cat engage in spray-marking, a kind of urination where fluid is sprayed outward in order to claim territory with scent cues. Males engage in spray-marking more frequently than females, but both are known to do it upon reaching the age of 2 years.
As with other mammals, lion urine passes from the bladder to the outside through the urethra, a tube that runs through the vulva or penis.