Before jumping to conclusion you should make sure that your cat is actually spraying and not simply urinating. When it comes to spraying, cats tend to stand upright and spray a small amount on vertical surfaces. When cats urinate they simply squat and eliminate large amounts on horizontal surfaces only. There are many reasons that make cats urinate outside their litter box. Some of them are medical reasons: kidney failure, urinary tract stones or crystals, diabetes and arthritis. What Causes Spraying Cat can find out many information about each other just from urine. Sometimes they urinate just to mark their territory, other times they are stressed or afraid of new things like other cats or simply new furniture.