That is a very good question.
The protein and microalbumine are not really signs of infection.
And the lack of anything growing on culture...assuming a good lab...makes any infection very highly unlikely, if not impossible, but this then has to rest on clinical assessment...and.....what is wrong with the kidney.
Only the white cell count would indicate infection of the urinary track.
But it might also indicate nephritis or inflammation of the kidney from other causes.
To sort this out, I would want to see a protein to creatinine ration...if not a 24 hour urine collection for protein.
1 gram for example, would be in the nephritic range.
Of course having only one kidney all of this should be under the consult of a nephrologist right now.
Let me know if you have further questions, details or need clarification, just use reply.......