Urinary Blockage in a cat question?

My cat Bugsy went to the animal hospital, last Saturday, cause he was not urinating and he started to throw up. The vet said that he was totally blocked. They put a catheter in him and said that there was lots of blood in his urine. They said they pulled the catheter Wednesday morning because his urine was clear. They kept him over night to monitor him and to see if he would urinate on his own. I called to check on him this morning. They said that they had to put the catheter back in because when Bugsy tried to urinate only a little bit came out and now there is more blood in his urine. They also said that when he had the catheter in he seemed really relaxed and he was acting like a normal cat. They said for me to plan on him being there for the weekend. Does anyone know how long it usually takes for a cat that was blocked to start urinating on their own? I miss my poor little guy. It's been 6 days since I've seen him.