Yeah I thought it was an enlarged prostate. Wonder if PharmTech09 was right about the micturition pathway and whether women get urinary retention to the same level?
I remember hearing a while ago that squatting was the best way to get the flow going and to piss out as much as possible. Maybe this could help (although you'd need to do it outside!)
I remember when I was at my worst on Heroin, I couldn't piss and it drove me nuts!
The only way I could make it happen was to stand in my shower, and turn the water on hot and let the warm water come down on me and that would usually do the trick!