The urinary tract is a system of organs. Wastes are filtered from the blood to make urine. It moves through the tract until it passes from the body.

The urinary system is made up of:

  • Two kidneys—filter wastes from blood and make urine
  • Two ureters—tubes that move urine from the kidneys to the bladder
  • Bladder—a hollow organ that holds urine until you’re ready to pass it
  • Urethra—a tube that passes urine out of the body from the bladder

A UTI can happen in any of these structures.

The Urinary Tract

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A UTI happens when bacteria on the skin, genitals, or rectal area get into the urethra. Once there, they grow and spread. A UTI can also be caused by:

  • A medical procedure or surgery.
  • Placing a catheter—A tube placed through the urethra and into the bladder. Bacteria climb the tube into the bladder.
  • Having sex.

Many types of bacteria can cause a UTI. Rarely, they can be caused by fungi. In children, they can be caused by viruses.