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Pyelonephritis (kidney infection)

Pokenga whanewhane

urinary system showing kidneys, ureters, bladder, and urethraPyelonephritis (pie-lo-nef-rite-is) is a painful bacterial infection of one or both of your kidneys.

If it is treated early, there should be no serious harm. If it is left untreated, it can get worse and cause kidney damage.

Most kidney infections are one-off and come on quite quickly. This is called acute kidney infection.

Repeated episodes of acute kidney infection can lead to chronic (long-lasting) kidney infection. Chronic kidney infection is rare, but it can lead to long-term kidney problems or even kidney failure.

Causes of kidney infections

Kidney infections usually happen because of a germ (bacterium) that enters your urethra (the tube you pass wee through) from the surrounding skin. It then travels into your bladder and up into your kidneys.

Anyone can get kidney infections, although they are more common in women. This is because their urethra is shorter, which makes it easier for the bacteria to reach the bladder before moving to the kidneys.

Other factors than can increase the risk of developing pyelonephritis include:

If the infection just causes a urine infection in your bladder, it is called cystitis. It only becomes pyelonephritis if it travels up to your kidneys.

Chronic kidney infection is usually caused by scarring of your kidneys, repeated urine infections or permanent defects in your kidneys at birth.

Symptoms of kidney infections

The symptoms of kidney infection can include:

Diagnosing kidney infections

Acute (suddenly occurring) kidney infection needs urgent medical attention. So, if you have the above symptoms, see your general practice team or after-hours doctor as soon as possible.

Your general practice team will examine you and ask you questions about your general health. They will diagnose a kidney infection by getting you to have a urine test. Sometimes you might need a blood test to check for signs of infection and to measure your kidney function.

Treating kidney infections

While kidney infections can become serious, they can almost always be cured. But it is best to get them treated quickly to prevent any complications. Although complications are rare, they can cause permanent damage to your kidneys.

Your doctor will usually prescribe antibiotics to get rid of the infection and simple pain relief to dull the pain and lower your temperature. They will also tell you to drink plenty of fluids. Make sure you finish all the antibiotics you are prescribed, even if you are feeling better.

If the infection is severe or does not clear up quickly with antibiotics, you may need to go to hospital.

Preventing kidney infections

You can do some things to reduce your risk of getting a kidney infection:

There is some evidence that cranberry juice or supplements may help prevent UTIs in women and children though not in pregnant or older people. There is no standard recommendation of how much cranberry you need.

In New Zealand, we mostly have cranberry drinks rather than cranberry juice. Cranberry drinks may contain as little as 3% cranberry juice. If you have cranberry drinks, it is best to choose the "light" or "low sugar" varieties as the regular varieties have a high amount of sugar.

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Written by HealthInfo clinical advisers. Last reviewed April 2023.


See also:

Overview of your kidneys

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