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Kidney infection - What is a kidney infection?

BMJ Group Medical Reference


Having a kidney infection can make you feel very ill, but if you don't have any other health problems and you get the right treatment, you should make a quick recovery. Kidney infections can affect men and women of all ages, but they're most common in women.

Most of the research has looked at women who aren't pregnant, so this information is mostly for them. Pregnant women may need to be treated in hospital.

Although most of the research has looked at women, treatment is similar for men and women.

We've brought together the best research about kidney infections and weighed up the evidence about how to treat them. You can use our information to talk to your doctor and decide which treatments are best for you.

Your kidneys are the organs in your body that make urine. You have two of them, each one about the size of a fist. They sit near the middle of your back, just below your ribs. They filter water and waste products out of your blood to make urine.

Urine drains from your kidneys down tubes called ureters. You have two ureters, one for each kidney. Both ureters empty into your bladder. Urine is stored in your bladder until you go to the toilet. When you urinate, urine passes out of your body from the bladder through a tube called the urethra.

The part of your body that makes and gets rid of urine is called your urinary tract. Your urinary tract includes your kidneys, ureters, bladder, and urethra.

You can get an infection in your urinary tract when tiny organisms, usually bacteria, get into your urethra and start to multiply.[1]

An infection that stays in your urethra is called urethritis. If it spreads to your bladder, it's called cystitis. Doctors sometimes call infections in your bladder or urethra lower urinary tract infections.

An infection in the lower part of your urinary tract may travel up your ureters to infect one or both kidneys. The medical name for a kidney infection is pyelonephritis. Doctors sometimes call kidney infections upper urinary tract infections.

If a doctor just says "urinary tract infection" or "UTI", they probably mean urethritis or cystitis. To read more, see our information on Cystitis.

There are two main types of kidney infections: uncomplicated and complicated.[2][3][4]

  • An uncomplicated kidney infection occurs when a person with a normal urinary tract and a healthy immune system gets infected with a common type of bacteria. This type of kidney infection is most common in women aged 18 to 40.

  • A complicated kidney infection happens when the infection is more serious for some reason. It might be caused by bacteria that aren't as easy to kill with drugs. Or you could have another medical condition that makes your kidney infection worse, or means your body can't fight it off as well as it should.

To learn more, see Types of kidney infection.

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Last Updated: October 03, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
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