Could you tell me how long it takes your urinary tract infection to reach the kidneys?

Kidney infection. Kidney infection (pyelonephritis) generally causes fever, chills and very significant flank pain. One generally feels "sick". Bladder infection (cystitis) rarely causes systemic symptoms. Discomfort in the pelvic area and irritative voiding symptoms are typical. In general, a bladder infection should not ascend to the kidneys unless there is an anatomic abnormality with the ureters. (reflux).