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Kidney infection

 

A kidney infection is a painful, unpleasant illness that usually happens when bacteria travels up from your bladder into one or both of your kidneys. 

It's different from - and more serious than - cystitis, which is a common infection of the bladder that makes urinating painful.

Kidney infection, medically known as pyelonephritis, doesn't usually pose a serious threat to your health if treated promptly, but it can make you feel very unwell. And, if a kidney infection isn't treated, it can get worse and cause permanent kidney damage.

Often the symptoms come on quickly, within a few hours, and they can make you feel feverish, shivery, sick and with a pain in your back or side.

When to see your GP

You should see your GP quickly if you have symptoms of a kidney infection.

Most kidney infections need prompt treatment with antibiotics. That's to stop the infection from damaging the kidneys or spreading to the bloodstream. You may need painkillers too.

If you're especially vulnerable to the effects of an infection, for example if you have a pre-existing health condition or you're pregnant, you may be admitted to hospital as a precaution and treated with antibiotics that are given by intravenous drip into a vein.

Read more about treating a kidney infection.

What causes a kidney infection?

The kidneys are two bean-shaped organs on either side of the body, just underneath your ribcage. Their main role is to filter out waste products from blood. These waste products, along with excess fluid, are then converted into urine and passed out of the body.

A kidney infection usually happens when bacteria, often a type called E. coli, accidentally gets into the urethra (the tube through which urine passes out of the body) from the anus and then travels up through the bladder into one of the kidneys.

In most cases of kidney infection, only one kidney is affected.

Read more about the causes of a kidney infection.

Who's at risk?

Kidney infections aren't that common. It's estimated that 1 in every 830 people will develop a kidney infection in any given year.

They can happen at any age, but are much more common in women. In fact, women are six times more likely to get a kidney infection than men. This is because a woman's urethra is shorter than a man's, which makes it easier for bacteria to reach their kidneys.

Younger women are most at risk because they tend to be sexually active, and having frequent sex increases the chances of getting a kidney infection. Kidney infections are also slightly more common during pregnancy.

Younger children are also vulnerable to developing kidney infections because their small urinary tract makes it easier for bacteria to reach their kidneys. It is estimated that 1 in 20 cases of high temperature in children is actually a result of a kidney infection.

There are steps you can take to reduce your risk of kidney infection. Find out more about how to prevent kidney infection.

Glossary   Kidneys
Kidneys are a pair of bean-shaped organs located at the back of the abdomen. They remove waste and extra fluid from the blood, and pass them out of the body as urine.
Bladder
The bladder is a small organ near the pelvis that holds urine until it is ready to be passed from the body.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease, and some are good for you.

The symptoms of a kidney infection include:

  • pain in your side
  • pain and discomfort in your lower back and around your genitals
  • high temperature (it may reach 39.5ºC or 103.1ºF)
  • shivering
  • chills
  • feeling very weak
  • loss of appetite
  • feeling sick
  • being sick
  • diarrhoea

You can also have other symptoms if you also have cystitis or urethritis (an infection of the urethra). These additional symptoms may include:

  • pain or a burning sensation during urination
  • the need to urinate frequently or urgently
  • feeling that you're unable to urinate fully
  • cloudy, bloody or bad smelling urine
  • pain in your lower abdomen

Children

Children with a kidney infection may also have additional symptoms such as:

When to seek medical advice

Contact your GP if you have a high temperature, persistent pain, or if you notice a change to your usual pattern of urination.

Kidney infections require prompt treatment with antibiotics to help relieve symptoms and prevent complications developing.

Now, find out how kidney infection is diagnosed.

Glossary Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Chronic
Chronic usually means a condition that continues for a long time or keeps coming back.
Diarrhoea
Diarrhoea is the passing of frequent watery stools when you go to the toilet.
Fever
A high temperature, also known as a fever, is when a person's body temperature rises above the normal 37°C (98.6°F).
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood, and pass them out of the body as urine.
Pain
Pain is an unpleasant physical or emotional feeling, which your body produces as a warning sign that it has been damaged.
Vomiting
Vomiting is when you bring up the contents of your stomach through your mouth.

If you have a kidney infection

Make sure that you get plenty of rest. A kidney infection can be physically draining, even if you're normally healthy.

It may take up to two weeks before you're fit enough to return to work.

A kidney infection happens when bacteria enter and infect one or both of your kidneys. The bacteria are usually a type called E. coli, which live in your bowel.

The bacteria get in through the opening of the urethra and move upwards through your urinary tract, first infecting your bladder and then your kidneys (see box, right).

It's thought that one way the bacteria get in to your urinary tract is by accidentally spreading from your anus to your urethra. This can happen if you wipe your bottom after going to toilet and the soiled toilet paper comes into contact with your genitals. It can also happen during sex.

In rare cases, a kidney infection can develop if bacteria or fungi infect the skin and the infection spreads through your bloodstream and into your kidney. However, this type of infection usually only occurs in people with weakened immune systems. 

Who's most likely to get a kidney infection?

Women are most at risk of developing a kidney infection as well as other urinary tract infections (UTIs), such as cystitis.

In women, the urethra is closer to the anus than it is in men, making it easier for bacteria from the anus to accidentally enter the urethra. The female urethra is also much shorter than the male urethra (which runs through the penis). This makes it easier for bacteria to reach the bladder and move into the kidneys.

Other factors can put you more at risk of developing a kidney infections. They are listed below.

  • Having a condition that blocks, or obstructs, your urinary tract, such as kidney stones.
  • Having a condition that prevents you emptying your bladder fully, such as an injury to your spinal cord.
  • Having a weakened immune system - for example, due to type 2 diabetes, or as a side effect of treatments that weaken the immune system, such as steroid tablets or chemotherapy.
  • Having an infection of the prostate gland called prostatitis, because the infection can spread from the prostate gland into the kidneys. 
  • Being female and sexually active. This is because sexual intercourse can irritate the urethra and allow bacteria to travel more easily through it and into your bladder.
  • Having a urinary catheter (a thin, flexible tube that's inserted into your bladder to drain away urine).

Kidney infections in men

Kidney infections are much less common in men than in women, mainly because the male urethra is shorter and further from the anus than in women. Also, in men, the skin and tissue around the urethra is drier than in women, which means that bacteria do not breed as easily. And, the fluid that's produced by the prostate gland has an anti-bacterial effect.

However, some men do get kidney infections, particularly if they:

  • have prostatitis. Researchers have found that over 90% of men with a kidney infection also have a prostate gland infection
  • have anal sex

Now, find out how kidney infections are diagnosed.

The urinary tract

The urinary tract is made up of the:

  • kidneys, which extract waste materials from the blood and convert it into urine
  • ureters, the tubes that run from the kidney to the bladder
  • bladder – a ‘balloon-shaped’ organ that  stores urine
  • urethra – the tube that runs from the bladder through the penis (in males) or vulva (in females) through which urine is passed

An infection that develops inside the urinary tract is known as a urinary tract infection (UTI). As the parts of the urinary tract  are all connected, a UTI that develops in one section can spread to another.

 

To work out if you have a kidney infection, your GP will ask you about your symptoms and your recent medical history. They'll also assess your general health by taking your temperature and measuring your blood pressure.

Urine test

A urine test can help to establish whether you have a urinary tract infection (UTI). The test involves taking a small sample of urine and checking it to see if there's any bacteria in it.

But a urine test can't tell whether the infection, if you have one, is in your kidneys or another part of your urinary system, such as your bladder.

For your GP to be confident that you have a kidney infection, you need to have a positive urine test plus certain distinctive symptoms, such as a fever or a pain in your side.

Hospital scans

Further testing is usually only required if:

  • your symptoms fail to respond to treatment with antibiotics
  • your symptoms suddenly get worse
  • you have additional symptoms that aren't usually associated with a kidney infection
  • you're prone to kidney infection complications

In these circumstances, two types of hospital scan can check your urinary tract for signs of problems. They are:

  • a computer tomography (CT) scan - the scanner takes a series of X-rays and a computer is used to assemble them into a detailed image of your urinary tract
  • an ultrasound scan - this uses sound waves to build-up an image of the inside of your body

Read about how a kidney infection is treated.

Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease, and some are good for you.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart. 
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood, and pass them out of the body as urine.
Magnetic resonance imaging
MRI stands for magnetic resonance imaging. Magnets and radio waves are used in order to take detailed pictures of inside the body.
Urine sample
Urinalysis/UA is when a urine sample is tested, usually to check for any signs of infection, or ti check protein or sugar levels.
X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.

Handing in a urine sample

If your GP asks for a urine sample, you'll be given a container and told how to collect the urine. 

You can do this in the surgery, or later at home.

When you've collected the sample, screw the lid of the container shut, label it with your name, date of birth and the date, then wash your hands thoroughly.  

If you're at home, put the container in a  plastic bag, seal it and keep it in the fridge.

Ideally, hand the sample in at the surgery within four hours.  

Once you've been diagnosed with a kidney infection, your GP will discuss your treatment with you.

Most people can be treated at home by taking a course of antibiotics and possibly painkillers too.

Antibiotics

If you're being treated at home, you will be prescribed a seven-day course of antibiotic tablets or capsules.

For most people, apart from pregnant women, antibiotics called ciprofloxacin or Co-amoxiclav are usually recommended.

Common side effects of ciprofloxacin include feeling sick and diarrhoea.

Co-amoxiclav sometimes makes the contraceptive pill and contraceptive patches less effective, so you may need to use another form of contraception during the course of treatment.

A 14-day course of an antibiotic called cefalexin is recommended for pregnant women.

Contact your GP for advice if your symptoms fail to improve within 24 hours after starting to take antibiotics.

Painkillers

Taking a painkiller, such as paracetamol, should help to relieve symptoms of pain and a high temperature.

Drinking water

It's also important to drink plenty of fluids because this will help prevent you becoming dehydrated, and it will help to flush out the bacteria from your kidneys. Aim to drink enough so that you're frequently passing pale coloured urine.

Self-help tips

If you have a kidney infection, try not to 'hover' over the toilet seat when you go to the loo, because it can result in your bladder not being fully emptied.

Make sure that you get plenty of rest. A kidney infection can be physically draining, even if you're normally healthy and strong. It may take up to two weeks before you're fit enough to return to work.

Treatment at hospital

In some instances, you'll need to be treated in hospital rather than at home. Hospital treatment may be needed if:

  • you're severely dehydrated
  • you're unable to swallow or keep down any fluids or medications
  • you have additional symptoms that suggest you may have blood poisoning, such as a rapid heartbeat and losing consciousness
  • you're pregnant and you also have a high temperature
  • you're particularly frail and your general health is poor 
  • your symptoms fail to improve within 24 hours of starting treatment with antibiotics
  • you have a weakened immune system
  • you have a foreign body inside your urinary tract, such as a kidney stone or a urinary catheter you have diabetes
  • you're over 65 years old
  • you have an underlying condition that affects the way your kidneys work, such as polycystic kidney disease or chronic kidney disease

If you're admitted to hospital with a kidney infection, you'll probably be attached to a drip so that you can be given fluids to help keep you hydrated. Antibiotics can also be given through the drip.

You'll have regular blood and urine tests to monitor your health and monitor how effectively the antibiotics are fighting off the infection.

Most people respond well to treatment. As long as there are no complications, they're usually well enough to leave hospital within three to seven days.

Now, read about the complications of kidney infection.

Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Being sick
Vomiting is when you bring up the contents of your stomach through your mouth.
Dehydration
Dehydration is an excessive loss of fluids and minerals from the body.
Drip
A drip is used to pass fluid or blood into your bloodstream, through a plastic tube and needle that goes into one of your arteries or veins.
Fever
A high temperature, also known as a fever, is when a person's body temperature rises above the normal 37°C (98.6°F).
Heart
The heart is a muscular organ that pumps blood around the body.
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Liver
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.
Pain
Pain is an unpleasant physical or emotional feeling, which your body produces as a warning sign that it has been damaged.
Painkillers
Analgesics are medicines that relieve pain. For example paracetamol, aspirin and ibuprofen.
Urine test
Urinalysis/UA is when a urine sample is tested, usually to check for any signs of infection, or to check protein or sugar levels.
Vein
Veins are blood vessels that carry blood from the rest of the body back to the heart.

Seeing a specialist

Your GP may refer you to a hospital specialist called a urologist if they think there may be an underlying problem with your urinary tract that's making you more vulnerable to kidney infections.

Urologists are doctors who specialise in treating conditions that affect the urinary tract.

It's standard practice to further investigate all men with a kidney infection simply because the condition is much rarer in men. Only women who have had two or more kidney infections tend to be referred.

There are three main complications of a kidney infection. They are:

  • kidney abscess
  • blood poisoning
  • severe infection

Kidney abscess

A kidney abscess is a rare but serious complication of a kidney infection. It's when pus develops inside the tissue of the kidney.

You're thought to be most at risk of developing a kidney abscess if you have diabetes.

The symptoms of a kidney abscess are similar to those of a kidney infection. The most common are:

  • a high temperature of 38ºC (100.4ºF) or above
  • chills
  • abdominal pain
  • loss of appetite
  • pain when passing urine

Kidney abscesses are potentially serious because the bacteria inside the abscess can spread to other parts of your body, such as your bloodstream or lungs, and can be fatal.

Smaller abscesses can usually be treated with intravenous antibiotics. Surgery is usually required for larger abscesses. It normally involves draining the pus out of the abscess using a needle that's inserted into the kidney.

Blood poisoning

Blood poisoning is another rare, but potentially fatal, complication of kidney infection. It happens when bacteria spreads from the kidneys into the bloodstream. Once bacteria are in your blood, the infection can spread to any part of your body, including all of the major organs.

In someone with a kidney infection, the symptoms of blood poisoning, which is medically known as sepsis, include:

  • low blood pressure, which makes you feel dizzy when you stand up
  • confusion or disorientation
  • excessive sweating
  • uncontrollable shaking or shivering
  • high temperature or, alternatively, a body temperature that's lower than usual; under 36ºC (96.8ºF)
  • pale skin
  • rapid heart beat
  • breathlessness

Blood poisoning is a medical emergency that usually requires admission to a hospital intensive care unit (ICU) while antibiotics are used to fight the infection.

If you're taking certain medications for diabetes, such as metformin or angiotensin-converting enzyme (ACE) inhibitors, they may have to be temporarily withdrawn until you recover. This is because they can cause kidney damage during an episode of blood poisoning.

Severe infection

Another rare but potentially fatal complication of a kidney infection is a condition called emphysematous pyelonephritis (EPN).

EPN is a severe infection where the tissues of the kidneys are rapidly destroyed and the bacteria that are causing the infection begin to release toxic gas, which builds up inside the kidneys.

The exact cause of EPN is unclear, but almost all cases are in people with diabetes.

The usual treatment is emergency surgery to remove some, or all, of the affected kidney. It's possible to live a full and active life with only one kidney.

Abscess
An abscess is a lump containing pus, which is made by the body during infection.
Antibiotic
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease, and some are good for you.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Dose
Dose is a measured quantity of a medicine to be taken at any one time, such as a specified amount of medication.
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood, and pass them out of the body as urine.

Who's at risk?

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

  • have diabetes
  • have chronic kidney disease 
  • have sickle cell anaemia
  • have had a kidney transplant (particularly in the first three months after the transplant)
  • have a weakened immune system
  • are over-65
  • developed the kidney infection while in hospital
  • are pregnant  

Most kidney infections develop following an infection of another part of your urinary tract, such as cystitis.

So, the best way to prevent a kidney infection is to keep your bladder and urethra free from bacteria. These self-help tips explain how to do this.

Drink plenty of liquids

Drinking plenty of liquids, particularly water, will help to wash bacteria from your bladder and urinary tract.

Drinking cranberry juice or taking cranberry extracts may also help to prevent urinary tract infections. But steer clear of cranberry juice or extracts if you're taking warfarin (a medicine that's used to prevent blood clots). Cranberry juice can make the effects of warfarin more potent, so there's a risk of the interaction between the two causing excessive bleeding.

Treat constipation

Constipation can increase your chances of developing a urinary tract infection (UTI), so try to treat any constipation promptly.

Recommended treatments for constipation include:

  • increasing the amount of fibre in your diet (to 20-30g of fibre a day)
  • using a mild laxative
  • drinking plenty of fluids

See your GP if your symptoms don't improve after 14 days (or seven days for children with constipation).

Read more about how to treat constipation.

Be careful with contraceptives

If you keep getting urinary tract infections (more than three a year is considered high), avoid using spermicide-coated condoms or diaphragms. This is because spermicide can stimulate the production of bacteria. 

Stick to lubricated condoms without spermicide because unlubricated ones can irritate the urethra, making it more vulnerable to infection.

Useful Links

Toilet tips

To help keep your urinary tract free from bacteria:

  • go to the toilet as soon as you feel the need to urinate, rather than holding it in
  • wipe from front to back after going to the toilet
  • practise good hygiene by washing your genitals every day and before having sex
  • empty your bladder after having sex
  • if you're a woman, avoid ‘hovering’ over a toilet seat as this position can often leave urine behind in the bladder

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.