YOU HAVE TO READ THIS...
For cats who continue to experience urethral obstruction despite proper medical management, a surgical procedure called a perineal urethrostomy may be suggested. The surgery involves removing much of the penis and the narrow portion of the urethra, leaving a wider opening for the remaining portion. Side effects of surgery can include bleeding for up to ten days after surgery, narrowing at the surgical site, urinary incontinence, and a greater incidence of other kinds of bladder diseases. For these reasons, perineal urethrostomy is usually considered to be a last resort.
http://www.vet.cornell.edu/fhc/resources/brochure/urinary.html
My male cat had this problem as well. Four blockages in a two year time. The vet said this was the surgery he needed to have. Low and behold, a change of diet (to Science Diet), weight loss, and exercise solved the problem. He lived to be 14 years old.