To better understand urinary tract infections, it helps to understand the anatomy of the kidneys and genitourinary tract.

The kidneys are located in the back of the abdomen, below the ribcage and on either side of the spine. Each kidney weighs about 1/4 pound (0.6 kg) and is about the size of a fist. The kidneys filter waste from the bloodstream and produce urine. The kidneys also regulate the salt and water balance for the body. Urine leaves the kidneys and travels to the bladder via the ureters.

Anatomy examples:

• Kidney
• Kidney cross section
• Kidney cross section close-up
• Kidney collecting system

In an adult, the bladder can hold 10 to 20 ounces of urine -- about as much liquid as in one can of soda. Urine is carried out of the body through the urethra, a tube at the bottom of the bladder.

The urinary tract is broken down into two areas:

• Upper urinary tract:
• Includes the kidneys and ureters
• Lower urinary tract:
• Includes the urethra and bladder in women
• Includes the urethra and bladder in men