Blacklight to find all sources then cut out and remove drywall, doors, baseboards/trim, tack strips, cabinets (anything the urine touched). You CAN NOT surface clean this out. Ozone machine for 2-3 days with no one present then let air out and seal with kilz or pet treat surrounding areas. Replace all removed items and areas. It's costly and time consuming, but only way to really get smell out. As mentioned before, don't just enzyme treat and cover up as this never works.