Some companies make biological urine digesting products eg JohnsonDiversey's Stench & Stain Digestor. It's recommended for carpets but should work on wood. Try in a small area 1st as it may cause some discoloration. An easier solution would be Fabreze (Wal*Mart). Recommended for fabrics, but would be safer on the wood than the S&SD; easier to get hold of too.