Urinary tract infections are the most common of all bacterial infections and occur when bacteria grow in the bladder , kidneys , ureters , or urethra . Urinary tract infections are more common in women than in men, and are also common in older adults .

If not treated, urinary tract infections (UTIs) may cause serious, possibly life-threatening problems and permanent damage to the urinary tract.

Repeated UTIs in infants and children often indicate a problem with the shape or structure of the urinary tract. Structural problems may require special treatment and long-term steps to prevent permanent kidney injury.

Classification

Urinary tract infections are classified according to their location. Most are classified as bladder infections ( cystitis ) or kidney ( pyelonephritis ) infections. UTIs also include urethritis .

In men, prostatitis and epididymitis are common complications of UTIs. Prostate problems are the most common cause of recurrent urinary tract infections in men. ¹ See the topic Prostatitis for more information.

Urinary tract infections that do not cause symptoms are called asymptomatic bacteriuria . These types of infections often affect pregnant women, as well as older adults or those who require a catheter to urinate