My heavyweight, Dakota, had the PU surgery. It was really just a freaky occurance that led us to discover his blockage. I came home from work, and knew something was wrong. Daks was vocalizing and straining right in front of me. I scooped him up, got Jonah back into the car, and we went to the ER vet.

They examined him and said his bladder was empty, that it was UTI, and were JUST ready to d/c us when the vet said, "the next step would be an xray". Fo whatever reason, I asked him to go ahead and do it. Turns out, Daks was 100% blocked, and the ER vet called the surgery vet and got him an appointment for the next day. They kept him overnight, and I did the transport.

As it turns out, Daks had the largest, and most oddly shaped crystal the surgeon had EVER seen. He had the PU, and seems fine, years later.

My point? Push for an xray or ultrasound. My belief is that is the ONLY sure test for a blockage, when a kitty presents, without a physical finding.

Good luck.