I had a kidney infection in feb 2012 every since then I've had a niggling pain around the area of my left kidney. When I went to the doctors about they said it should go in time its been nearly 12 months and its still there. Also I've noticed that I am needing the toilet less as well should I be worried.

Worried ? Maybe not, concerned and going back to the doctor, or another doctor for a second opinion yes.

What types of tests, CAT scans and other things did they do, to decide that there was nothing to worry about ?

Thank you for your reply.
When I went to the doctors about this the only thing he did was test my urine which he said was clear he also felt my stomach and my back and when I said it hurt he just said that id pulled a muscle.