Cat Urine Stain on Clothing?

First of all, even if your top is white, don't bleach it! That will just set the stain. First go to a pet store that sells enzyme based urine remover. Put a small amount on the shirt and leave for 24hr to see that it won't damage or fade your top. If it doesn't I'd soak your stain in it first. Rub the stain as long as it doesn't damage the fabric. After you've done that and let it set for a while to "do it's thing", I'd then rinse it with clear water, and if there is any stain remaining, further treat it with some Oxyclean dissolved in water and liquid detergent.

That really should do it. You could use hydrogen peroxide instead of Oxyclean if you have some, but I think the Oxy works better. These things have saved more that one of my tops, and no one ever knew there was a stain, no stain-no odor. Best of luck.