A urinary tract infection, or UTI, is an infection of the urinary tract. The infection can occur at different points in the urinary tract, including:

Bladder -- An infection in the bladder is also called cystitis or a bladder infection.

Kidneys -- An infection of one or both kidneys is called pyelonephritis or a kidney infection.

Ureters -- The tubes that take urine from each kidney to the bladder are rarely the only site of infection.

Urethra -- An infection of the tube that empties urine from the bladder to the outside is called urethritis.

Most UTIs are caused by bacteria that enter the urethra and then the bladder. The infection most commonly develops in the bladder, but can spread to the kidneys. Most of the time, your body can get rid of these bacteria. However, certain conditions increase the risk of having UTIs.

Women tend to get them more often because their urethra is shorter and closer to the anus than in men. Because of this, women are more likely to get an infection after sexual activity or when using a diaphragm for birth control. Menopause also increases the risk of a UTI.

The symptoms of a bladder infection include:

Cloudy or bloody urine, which may have a foul or strong odor

Low grade fever in some people

Pain or burning with urination

Pressure or cramping in the lower abdomen or back

Strong need to urinate often, even right after the bladder has been emptied

Complications may include:

Life-threatening blood infection (sepsis) -- The risk is greater among the young, very old adults, and people whose bodies cannot fight infections (for example, due to HIV or cancer chemotherapy).

Kidney damage or scarring.

Kidney infection.