Urine is one of a number of waste products that your body produces. Urine has passed through the kidneys and is effectively sterile.
Urine is somewhat acidic and salty, and most people urinate just over a liter per day. In terms of genital piercings and genital modifications, urine can be quite useful in that it automatically flushes out and helps to clean piercings such as the Prince Albert piercing and transurethral ampallangs and apadravyas — but be careful — some of these piercings can cause a showerhead effect.
Also keep in mind that while urine is usually free of bacteria, viruses, and fungi, it does contain fluids, salts, and waste products. (Consider that protein and drug tests are often performed with urine samples.) It also may contain bacteria, especially if you have a kidney, bladder, or urinary tract infection.
Some people experience stinging when they pee with a fresh genital piercing. This sensation can be reduced or eliminated by filling a cup with warm water, submerging your genitals into it, and peeing into the cup. In addition, it should be noted that infections from fresh piercings can in some cases cause a bladder infection.