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Kidney infection (pyelonephritis)


Expert reviewer, Professor Raj Persad, Consultant Urological Surgeon
Next review due September 2021

A kidney infection is called pyelonephritis and can make you feel unwell with a fever, sickness and pain. A kidney infection can vary from being mild to life-threatening. A kidney infection can also be acute, which means it lasts for a short time, or chronic (last for a long time). This information is about an acute kidney infection.


An image showing the location of the bladder and surrounding structures

About your kidneys

Your kidneys do a number of important jobs, such as controlling your blood pressure and the amount of fluid in your body. They also 'clean' your blood by filtering out water and waste products to make pee (urine).

Urine is produced by your kidneys and passed down two tubes (called ureters) to be stored in your bladder. When you go to the toilet, you pass urine out of your body through your urethra. Your urethra is the tube that carries the urine from your bladder and out of your body.

Symptoms of kidney infection

The symptoms of a kidney infection can vary from not having any, to mild or severe. Kidney infection symptoms can develop over a few hours or over the course of a day and may include:

  • pain in your back, tummy (abdomen) or sides (it may be only on one side)
  • a fever (a high temperature) and chills
  • feeling sick or vomiting

You may also have symptoms of a lower urinary tract infection. This is an infection in your bladder and urethra and the symptoms may include:

  • needing to go to the toilet to pee urgently, and often
  • a burning or stinging feeling when you pee
  • blood in your urine

If you have any of these symptoms, contact your GP.

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Diagnosis of kidney infection

Your GP will ask you about your symptoms and medical history. They’ll examine you and ask you to give a urine sample. This urine sample can be tested to see if you have an infection. It’s sometimes called a 'dipstick' test. Your GP may also send a urine sample to a laboratory to find out which type of bacteria is causing the infection.

If you have a severe kidney infection, you may need to go to hospital for more tests, which may include the following:

Treatment of kidney infection

If you get treatment for a kidney infection, you should usually recover after a few days or weeks. Exactly how long it will take you to recover will depend on how severe your kidney infection was.

Self-help

An important part of kidney infection treatment is to stay well hydrated so make sure you drink plenty of fluids. The best thing to drink is water. One way to tell if you’re hydrated is to check the colour of your urine – it should be pale-coloured.

If you feel tired and generally unwell, make sure you get plenty of rest.

Image showing hydration level by urine colour

Medicines

If you need pain relief, you can take over-the-counter painkillers such as paracetamol. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.

If your GP thinks you have a kidney infection, they’ll prescribe you antibiotics. Antibiotics used to treat a kidney infection include ciprofloxacin, co-amoxiclav and levofloxacin. You’ll probably need to take these for a week or two. It’s important to complete the full course of kidney infection antibiotics, even if your symptoms clear up before you finish them. This helps to stop the infection from coming back.

Hospital treatment

If antibiotics haven’t begun to work within 24 hours of starting them, you may need to go into hospital for treatment, or if, for example, you:

  • have pain that’s getting worse
  • are pregnant
  • have a high fever
  • are being sick and can’t drink or take medicines
  • develop septicaemia (blood poisoning)
  • are at risk of developing complications or have other health problems, such as diabetes or kidney disease

In hospital, you’ll probably have a drip put into a vein in your hand or arm to give you fluids and antibiotics.

Surgery

If tests show that you have a blocked ureter or kidney (if you have a kidney stone, for example) you may need an operation to allow urine to flow. An example is a nephrostomy. In this operation, a tube is put in to drain urine straight from your kidney into a bag on the outside of your body.

Causes of kidney infection

A kidney infection is sometimes caused by bacteria, such as Escherichia coli (E. coli) which usually live in your bowel. The bacteria can spread from your anus to your urethra, and then up to your bladder, ureters and kidneys. Bacteria can also get into your kidneys from your bloodstream.

You're more likely to develop a kidney infection if:

  • you have an abnormal kidney or urinary tract
  • you have a catheter (tube) that takes urine out of your body from your bladder
  • your ureter or kidney is blocked, for example by a kidney stone or an enlarged prostate gland
  • you’re pregnant
  • you have diabetes
  • your immune system is weakened, for example if you have human immunodeficiency virus (HIV/AIDS)
  • you have a urinary tract infection (UTI)
  • you have urinary incontinence

Complications of kidney infection

Most people don’t have any further problems from a kidney infection, but sometimes an infection can become serious and even life-threatening. Complications include:

  • an abscess (a collection of pus) in your kidney
  • your kidneys not working properly, which can lead to kidney failure
  • permanent scars developing on your kidneys
  • septicaemia (blood poisoning) – this can happen if bacteria get into your blood

You're more likely to develop complications if you:

  • have a severe infection
  • have type 1 or type 2 diabetes
  • are older (over 60)
  • have lots of kidney infections or a long-term infection despite being treated for it
  • already have kidney disease
  • have a catheter (tube) that takes urine out of your body from your bladder
  • have a weakened immune system – for example, if you have HIV/AIDS (which reduces your ability to fight infection)
  • have kidney stones

If you're pregnant and you develop a kidney infection, it can lead to complications for you and your baby. These include your baby being born early and being born small. If you have any of the symptoms of a kidney infection and you’re pregnant, go and see your GP or midwife as soon as possible.

Prevention of kidney infection

If you keep getting kidney infections or urinary tract infections (UTIs), your doctor may suggest you take antibiotics for longer. How long you need to take them for will depend on your personal circumstances.

To help stop UTIs from developing you can try these self-help tips.

  • Drink more fluids, such as water.
  • Go to the toilet to pee as soon as you feel you need to go.
  • Go to the toilet to pee after you have sex.
  • Wipe from front to back after using the toilet.
  • Don’t use perfumed soaps and deodorants in your genital area.

Some people take D-mannose (a type of sugar) or drink cranberry juice or take cranberry supplements to prevent UTIs. Cranberries have a substance in them that can stop bacteria from sticking to the walls of your bladder, and it’s thought this may help prevent a UTI. Overall, the research into these isn’t conclusive, but it may be something you want to try to see if it helps.

Frequently asked questions

  • When you’re pregnant, your body goes through a lot of changes. This can affect how well it gets rid of urine and how easy it is for a bladder or kidney infection to develop.

    There are various reasons why you may be more likely to develop a kidney infection if you’re pregnant. Some of the main ones are listed below.

    • As your baby gets bigger, your womb (uterus) grows and pushes against your bladder and ureters (tubes that carry urine from your kidneys to your bladder). This can reduce the flow of urine and can cause an infection.
    • There is more sugar in your urine, which can help bacteria to grow.
    • Changes in your hormones make it harder for your body to fight infections.

    You’ll be offered a urine test early on in your pregnancy to check for infection. If you have an infection, getting treatment quickly can help to prevent any problems with your pregnancy.

  • You might hear your GP or nurse use the term UTI, or urinary tract infection. It means an infection of any part of your urinary system – your kidneys, bladder, ureters or urethra.

    A lower UTI is sometimes called cystitis and is an infection in your bladder. An upper UTI is an infection of your kidneys and your ureters (the tubes that carry urine from your kidneys to your bladder).

    The symptoms of a lower UTI include cloudy, dark or strong-smelling urine and problems passing urine. For example, you may pass small amounts of urine more often than usual, or find you need to get to the toilet very quickly, which is called urgency. You may also find that when you do pee, it stings or burns or it may have blood in it. Sometimes though, the symptoms may not be so obvious. For example, older people may feel confused as the only symptom.

    If you have any of these symptoms, contact your GP.


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Related information

    • Pyelonephritis. PatientPlus. www.patient.info/patientplus, last checked 1 April 2016
    • Acute pyelonephritis. Medscape. emedicine.medscape.com, updated 15 November 2017
    • Kidney anatomy. Medscape. emedicine.medscape.com, updated 29 August 2017
    • Bladder anatomy. Medscape. emedicine.medscape.com, updated 28 June 2016
    • Acute pyelonephritis. BMJ Best Practice. bestpractice.bmj.com, last reviewed June 2018
    • Urological infections. The guideline. European Association of Urology. uroweb.org, published 2018
    • Urinary tract infection (lower) – women. NICE Clinical Knowledge Summaries. cks.nice.org.uk, last revised July 2015
    • Pyelonephritis – acute. NICE Clinical Knowledge Summaries. cks.nice.org.uk, last revised June 2013
    • Treatment for kidney infection (pyelonephritis). National Institute of Diabetes and Digestive and Kidney Diseases. www.niddk.nih.gov, published April 2017
    • Does stopping a course of antibiotics early lead to antibiotic resistance? Online Q&A World Health Organization. www.who.int, published July 2017
    • Nephrostomy. British Society of Interventional Radiology. www.bsir.org, accessed 25 September 2018
    • Kidney infection. American Kidney Fund. www.kidneyfund.org, accessed 25 September 2018
    • Urinary tract infection (UTI) and cystitis (bladder infection) in females. Medscape. emedicine.medscape.com, updated 19 July 2018
    • Urinary tract infections in pregnancy. Medscape. emedicine.medscape.com, updated 18 October 2017
    • Antenatal care for uncomplicated pregnancies. National Institute for Health and Care Excellence (NICE), 26 March 2008, www.nice.org.uk
    • Urinary tract infection in adults. PatientPlus. www.patient.info/patientplus, last checked 24 March 2016
  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, September 2018
    Expert reviewer, Professor Raj Persad, Consultant Urological Surgeon
    Next review due September 2021



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