We have already ruled out stones. The symptoms I have are not those of stones.
The urologist I used to work for would probably do an IVP next, I think. CT scans supposedly make it obsolete, but CT scans deliver quite a bit more radiation. He used IVPs to identify stones, mostly. Not all stones show on plain x-rays, but an IVP shows blockage even if the stone doesn't show up on the film.