What is a urinary tract infection (UTI) and how is it caused? The urinary tract is made up of the kidneys, ureters, bladder, urethra and (for guys) the prostate. A UTI can occur anywhere in the urinary tract, however, the most common UTIs occur in the bladder and are caused by bacteria. Urinary tract infections are the second most common type of infections and account for about six million doctor visits per year.
Normally, the structure of the urinary tract helps prevent infection. The bladder and ureters keep urine away from the kidneys, and the flow of urine (i.e. out the bladder, through the urethra) helps wash bacteria from the body.
Urinary tract infections are caused when bacteria (usually intestinal bacteria from the anus) cling to the opening of the urethra and make their way up this structure and into the bladder or other parts of the urinary tract.