Food and pet smells can be tough. Replacing carpet and painting walls is a good place to start, but no one will guarantee results. I had an ozone generator which has helped in some cases in the past, but it broke. Urine smells can be reduced with an enzyme treatment you can get at pet store. Treat the area and let it soak in.
I did sell a house this year with terrible cigarette smoke that actually stained the walls and coated light fixtures. We had to use a professional service and they used a hydroxyl / ozone generator. Both are professional and they create molecules which can follow the smoke into tiny spaces, and both processes effectively remove the smell.
Michael Foster http://www.myairandenergy.com/air-purification-units.html
I don't know if you've already tried, failed or succeeded, but in the future - open a bottle of white distilled vinegar. Pour it into an open bowl. Set it in the middle of the room. (Use one full bowl for each room)
Walk away for 24 hours. Be amazed at the loss of "that smell" when you come back!
Cat urine - hardest smell of all! Even when you eliminate it from human detection, another animal will be able to smell it! Soak it in the vinegar. Let dry thoroughly, then hope for the best.
Best to you! GhostbloggerMarie