What are the symptoms of a clogged kidney?

I have low back pain and frequent night urinantion (3 times)I also have groin pain and occasional low abdomen pain - below the navel.. I have had EXTENSIVE URO examinations with no pathology found. My Doc says I got a lumbar problem, but the MRI does not show any problem.
Maybe I have a kidney problem even though the last IVP showed no calcification ..Help??