The urinary tract makes and stores urine, one of the body's liquid waste products. The urinary tract includes the following parts:

  • Kidneys, which produce urine by removing waste and water from the blood
  • Ureters, the tubes that carry urine from the kidneys to the bladder
  • Bladder, the sac-like container for storing urine
  • Urethra, the tube that carries urine from the bladder to outside of the body

What is a urinary tract infection?

Normal urine contains no bacteria (germs). Sometimes, however, bacteria from outside the body get into the urinary tract, and cause infection and inflammation. This is a urinary tract infection. The infection can involve the urethra (a condition called urethritis), kidneys (a condition called pyelonephritis) or bladder, (a condition called cystitis). Cystitis is the most common type of urinary tract infection.

How common are urinary tract infections?

Urinary tract infections are very common, occurring in 1 out of 5 women sometime in their lifetime. One to 2% of children develop urinary tract infections. Each year, 8 million to 10 million visits to doctors are for urinary tract infections.

Who gets urinary tract infections?

Anyone can get a urinary tract infection, but they are more common in women. This is because the urethra in females is shorter and closer to the anus, where E. coli bacteria are common. Older adults also are at higher risk for developing cystitis. This increased risk may be due to incomplete emptying of the bladder related to various medical conditions, including an enlarged prostate or a bladder prolapse (i.e., falling down or slipping of the bladder from its usual position). If you get frequent urinary tract infections, your doctor may do tests to check for other health problems—such as diabetes or an abnormal urinary system—that may be contributing to your infections.

What are the symptoms of a urinary tract infection?

A urinary tract infection causes the lining of the urinary tract to become red and irritated, which may produce some of the following symptoms:

Other symptoms that may be associated with a urinary tract infection include:

What causes a urinary tract infection?

Urinary tract infections are caused by microorganisms—usually bacteria—that enter the urethra and bladder, causing inflammation and infection. The bacteria also may travel up the ureters and infect the kidneys.

More than 90 percent of cystitis cases are caused by E. coli, a bacterium normally found in the intestines.

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