Overview

Urinary tract infection (UTI) is a common infection that usually occurs when bacteria enter the opening of the urethra and multiply in the urinary tract. The urinary tract includes the kidneys, the tubes that carry urine from the kidneys to the bladder (ureters), bladder, and the tube that carries urine from the bladder (urethra). The special connection of the ureters at the bladder help prevent urine from backing up into the kidneys, and the flow of urine through the urethra helps to eliminate bacteria. Men, women, and children develop UTIs.

Types
Urinary tract infections usually develop first in the lower urinary tract (urethra, bladder) and, if not treated, progress to the upper urinary tract (ureters, kidneys). Bladder infection (cystitis) is by far the most common UTI. Infection of the urethra is called urethritis. Kidney infection (pyelonephritis) requires urgent treatment and can lead to reduced kidney function and possibly even death in untreated, severe cases.

Incidence and Prevalence
Approximately 8 to 10 million people in the United States develop a UTI each year. Women develop the condition much more often than men, for reasons that are not fully known, although the much shorter female urethra is suspected. The condition is rare in boys and young men.

Twenty percent of women in the United States develop a UTI and 20% of those have a recurrence. Urinary tract infections in children are more common in those under the age of 2.