Infections of the urinary tract are common. Urinary tract infections (UTI's) are caused by bacteria that invade the urinary system and multiply, leading to an infection. Women are affected more than men.

The urinary system consists of the kidneys, ureters, bladder, and urethra. The key elements in the system are the kidneys, a pair of purplish-brown organs located below the ribs toward the middle of the back. The kidneys remove liquid waste from the blood in the form of urine, keep a stable balance of salts and other substances in the blood, and produce a hormone that aids the formation of red blood cells. Narrow tubes called ureters carry urine from the kidneys to the bladder, a triangle-shaped chamber in the lower abdomen. Urine is stored in the bladder and emptied through the urethra.

There are three types of urinary tract infections:

Urethritis is infection of the urethra

Cystitis is infection of the bladder

Pyelonephritis occurs when bacteria ascend up the ureters and infect the kidneys.