as Birget has said, she is considered a senior kitty now and they do incorporate a whole new set of problems.I realize how hard this type of behavior can be on everyone and your kitty. There is never a simple answer . First, I have to say, it will be a little harder to retrain her since, she has been doing it since she was a kitten, so, you , need to see it from her point of view, she does not see this as wrong. Cats donot do thinks to get even with us or punish us for giving someone or something more attention..
As they others have gave you such very good advice I will try not to repeat it.. except the vet is the first and foremost place to start. Even though she has been healthy it does not mean at 11 she has not started to develope some disease which making urinating more urgent for them such as diabetes, and hyperthyroidism.. you need to have a full blood panel ran to make sure.
You have said this has been a long time problem so it would be hard to decide why she began to choose not to use the litter box in the begining. So we would have to start from scratch.. and she would need to be retrained which takes time and efforts. As sad and harsh as it sounds she would need to be limited to where she can go in the house and when you are not home. Kept in one room or large dog crate in a room where she can see her home and has all the comforts she needs.. here are some tips from a good cat book.
Thinking outside the Litter Box, Margret a Bonham
Believe ,it or not your kitty prefers to use her litter box. Cats donot want to eliminate where they eat,sleep,or hang out:they are programmed to be fastidious in this area. If your kitty is urinating outside the box something is dreadfully wrong. Unfortunately your kitty cannot verbalize what his problem is. Litter Box Abandonment. Example.. Have you ever stopped at a gas station or somewhere to go potty, it smelled awful,it was dirty, you had to hold your breath and the toilet was not flushed and so full you cannot flush it,. now think how your cat feels is it sparkling clean or is smelly or and icky. Does your kitty have to avoid land mines or does she have a clean place to walk. What may smell ok to you she cannot tolerate, cleaning agents you use to clean the box,
Keep it Clean
some guide lines
one cat two litter trays
if standard litter tray change once a week
recyled newspaper litter once a week
scoopable once a month
natural once a month
crystal once a month
This is a rule of thumb and this is removing solids on a daily basis or more as neede. If they are heavy users change more often
Sensitive sniffers: cats have such a strong sense of smell some may positively be picky when it comes to thier litters. The smell of perfume,or added scents will probabley be highly offensive to them. use unscented..
Location: oddly enough your cat will stop using his litter box because she doesn't like where you have put it. It might be to hard to get to, if you have a two leve house have a tray on each level. cats do like privace, think how you would feel if your toliet was where you had to sit in front of every one. Once a cat likes where her litter box is , they do not want you to move it.
Difference shape and size, some like them short and deep, mine likes her long and low as she is a big girl, a kitten needs a very low flat one. Sorry, this is sensitve issure here but important, Declawed cats oftne have litter box problems due to pain and sensitive feet. use soft litter such as wheat or corn clummping
Try different kinds til you find the litter she like. my girl will not use only crystals.. she can hold her urine til her eyes fall out, when we do the urine test with the beebee balls she goes almost a whole day.
Innapporpriat elimnation health problems can invaribley cause a cat to "think outside the box" This is a biggie because, quite frankly, a cat who doesn't feel good is more likely not to make it to her litter box all the time or to blame her litter box for her condition. CAt logic is pretty simple when it comes t o pain,Avoid whatever is causing it. your cat is not thinking her body is causing her pain but something in her enviroment is, If it is constipation, urinary infection, blockage and it hurts to use her litter tray then in cat lanuage, HER TRAY IS PUTTING THE BITE ON HER AND SHE IS NOT GOING TO USE IT.
sorry this is long retraining your kitty.
once a cat has developed an aversion to her litter tray, it may be difficult for her to think about using it again. After all she has had no problem where she is going now. The first step in retraining process is to clean up any areas your kitty has been using to go potty. Throw out anything that you can throw out.As long as your cat can locate th odor in those locations she will continue to use them.
Use a good enzymatic cleaner, you can get at your vet, on line or at a pet store. you must remove every trace of odor. Then purchase a boundary type spray to spray these areas, you may have to use it on a daily basis for a while. it is a spray to discourage spraying or urinatiing.. or pooing. Use double sided sticky tape in these areas or velco tape, but just one side of the velcro, they do not like the feel of sticky tape or velcro.
Then since your kitty has been doing this a long time you need to keep her in one room for a while. Making sure you give her time with the family for a few hours at a time. Make sure her tray is in her room with her, and anytime you visit her take her to her littler and set her in it, when she jumps right back out set her back in a say go. They will learn. When she does go, pet her, hug her tell her what a good girl she is, give her a treat.. do this every time you go in the room./ never punish her for mistakes. she will think it it the litter box hurting her and cats do not understand punishment. they do understand when you speak stern say no and walk away..
Slowly give her access to the house, but like a kitten take her to the tray when you get up, afrter she eats, drinks or play... not easy but can be done.. good luck.. pat
cats eyes say it all