Bladder sensations after surgery

Four weeks ago I had part of a disk and surrounding bone removed. For the second time in a year. Right after surgery going to the bathroom I noticed my bladder had no sensation of being full. I just thought it would pass in time. I did mention it to my Dr. on my three week exam, but he more or less just brushed it off as no big deal. There is no leakage yet because I empty my bladder when I know it's full. other wise it would leak. In the morning I drink two cups of coffee and usually run to the bathroom in the first 20 minutes. Now after 3 hours there is no feeling of a full bladder. Don't get me wrong, I don't mind it I just know it's not normal and it does worry me. My biggest fear is both parents had kidney failure so I am a little scared. What should be my next move? If my Dr. see's nothing wrong who do I talk to.