My cat, Lottie, had cystitis six times in a year and she actually passes lots of pure blood - not nice. After the third time the vet xrayed her and took a urine sample. There are different things which can cause similar symptons and you need to know what you are dealing with in order to treat correctly. They ruled out infection, crystals, stones, any unusual lumps and were able to confirm it was cystitis. So we slowly swapped Lottie over to eating wet cat food all the time and she has one cystease mixed with her food daily. Getting her tested as the besst thing I ever did for her - knowing what the medical problem is has made a great difference with the correct course of treatment and since that time she's had it just once in two years, so do ask about testing. It's not cheap, but the vets bills will soon add up if you are having to regularly go the vets. If it's down to something like crystals/stones, then your little once would need a special diet.