Introduction to Urinary Tract Infections (UTIs) By Talha H Imam, MD, University of Riverside School of Medicine Reviewed / Revised Jul 2021 | Modified Sep 2022 View Patient Education Urinary tract infections (UTIs) can be divided into upper tract infections, which involve the kidneys (pyelonephritis), and lower tract infections, which involve the bladder (cystitis), urethra (urethritis), and prostate (prostatitis).