We have an 11 yr old female and 9 yr old male. They have always been good re going outside to do their business. Our neighbour next door has 3 cats who have been there for many years. Recently our cats have been refusing to go outside. We can smell cat urine in the bedroom (unsure whether it is urine or cat marking territory) and the cats are frequently toy seeing and pooing in other rooms in the house. Found a whole load of runny poo in the basket where I keep all hats and gloves. We just don't know what to do and why there is such a change in behaviour. If we start putting cat litter in the house, will the cats end up using this and no longer want to go out? They are miaowing a lot more than usual too.