Why is my 19 year old cat suddenly urinating on the carpet?

You would need a trip to the vet to see if it truly struvite crystals. She may need a diet change. She also may need some fluids and an un-blocking. She may have hip-dysplasia and be having issues getting INTO the box and need a box with shorter sides. The truth is a 19 year old cat is very OLD cat. you must take this into consideration. Just like a senior/SENIOR citizen there are probably alot of things going on through her head. She may have trouble MAKING it to the box if there is only ONE box in your house. you may have to provide an ADDITIONAL box, especially near the area she is soiling. Make sure you completely clean the area with a protein breaker, like Nature's miracle so she doesn't re-soil this area. Take all these things into mind, but run her to the vet for a check up as well. She may have a UTI and need some med.'s as well. OR a combination of some of these solutions. If all else fails you may need to confine her to a smaller area with a box, because she is too old to let wander a larger area.

I'm no expert, but, maybe you should take that cat to the vet or some other doctor. There shouldn't be a lump on it's chin.