House soiling in cats, also called feline inappropriate elimination, is the most common behavioral complaint of cat owners. Problem behaviors can be urine and/or stool deposited outside of the litter box, or marking behaviors. Marking includes spraying urine on vertical locations.
Any medical condition that interferes with a cat's normal urination or defecation behavior can cause litter box problems. Inflammation of the urinary tract.
It's not that unusual for a cat to pee outside its litter box. its litter box for one of two general reasons: a medical problem or a behavioral issue.