Two weeks ago we took her to the vets because she was off her food. Felix AGAIL was no longer acceptable after 6 years. We took her to the vets where she had the once over and blood tests and all was ok. She's getting on for 10 so all good.
She now eats fine just not the Felix.
Anyway, yesterday afternoon she came flying down the garden into the house (no bushy tail or heckles) and then started miaowing for food.
As I was getting it I noticed her getting into the 'wee' position and then start wailing and yowling. Then she passes watery blood. 
She then ate her food, then went upstairs and did the yowling and passing watery blood again.
So off to the vets. Once over again, nothing untoward found, they think possibly stress cystitis. They gave me morphine which has to go on her gums and have given me those crystals for me to collect a wee sample.
This morning, she is completely fine, eaten two plates of food, wanting a fuss and wanting to go out just the same as every morning.
The crystals in the tray have been understandably ignored, and as I have to go out later this morning til late tonight and the sample has to be fresh, that will have to wait. If she will actually use it.
I just don't know what to think. She had an episode the same a few years ago minus the blood. Just the one off and back to normal.
Any ideas? More of a WWYD I guess. 
If we can't get the sample they said they will have her in to get it but she seems fine now.