UTIs (urinary tract infections) are the second most common type of infection in the body and account for about 8.3 million doctor visits each year. Women are especially prone to UTIs, and one in five women develops a UTI during her lifetime. But what defines a urinary tract infection? And what factors can cause or add to the risk of developing a UTI?

What is a UTI?
A UTI is an infection anywhere in the urinary tract. The urinary tract makes and stores urine and removes it from the body. Parts of the urinary tract include the:

Bladder - stores urine
Kidneys - collects waste from blood to make urine
Ureters - carries urine from the kidneys to the bladder
Urethra - a short tube that carries urine from the bladder out of the body during urination

A urinary tract infection limited to the urethra is called "urethritis". If bacteria move to the bladder, multiply into a bladder infection, this is called "cystitis". If cystitis is not treated promptly, bacteria may then travel further up the ureters to multiply and infect the kidneys, which is called "pyelonephritis".

UTIs have many possible causes.  Know what puts you at risk of developing an infection in the urinary tract and learn what causes urinary tract infections in the next section on causes and risk factors for UTI.