Kidney infection

A kidney infection (pyelonephritis) is a painful, unpleasant illness. It happens when bacteria travel from your bladder into one or both of your kidneys.

It's more serious than cystitis, a common infection of the bladder that makes urinating painful.

If you get treatment promptly, a kidney infection doesn't cause serious harm, but you will feel very unwell. If it isn't treated, it can get worse and cause permanent kidney damage.

Symptoms often come on within a few hours. You can feel feverish, shivery and sick, and have a pain in your back or side.

See a doctor if you have a fever and tummy, lower back or genital pain that doesn't go away, or if you notice a change in your usual pattern of urination.

Most kidney infections need prompt treatment with antibiotics, to stop the infection from damaging the kidneys or spreading to the bloodstream. You may need painkillers as well.

Some people are especially vulnerable to the effects of an infection, for example those with a pre-existing health condition or who are pregnant. If that's you, you may be admitted to hospital and given antibiotics through an intravenous drip.

After you take the antibiotics, you should feel completely better in about 2 weeks.

In rare cases, a kidney infection can cause further problems. These include blood poisoning (sepsis) and a build-up of pus in the kidney called an abscess.

A kidney infection usually starts when bacteria get into the urethra (the tube that carries urine out of the body). The bacteria are often a type called E. coli. From the urethra they travel up through the bladder and into the kidneys.

Kidney infections are relatively rare. It's estimated that one in every 830 people develops a kidney infection each year in the UK.

They can happen at any age, but they're much more common in women. In fact, women are 6 times more likely to get a kidney infection than men. The reason is that a woman's urethra is shorter, so bacteria reach the kidneys more easily.

Younger women are most at risk because they tend to be more sexually active, and having frequent sex increases the chances of a kidney infection.

Younger children are also vulnerable. Some are born with an abnormality of the urinary tract, and some have a condition called vesico-ureteric reflux, where urine flows backwards from the bladder up to the kidneys.

You can lower your chances of getting a kidney infection by keeping bacteria out of your bladder and urethra. Drinking plenty of fluids helps, and so does keeping your genitals clean and treating any constipation.

A kidney infection usually comes on quite quickly, over a few hours or a couple of days. The common symptoms are:

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

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

• pain or a burning sensation when you pass urine
• needing to urinate often or urgently
• feeling that you can't empty your bladder fully
• blood in your urine
• cloudy or foul smelling urine
• pain in your lower abdomen

A child with a kidney infection may also have other symptoms, such as:

• a lack of energy
• irritability
• poor feeding and/or vomiting
• not growing at the expected rate
• abdominal pain
• jaundice (yellowing of the skin and whites of the eyes)
• blood in the urine
• unpleasant smelling urine
• bedwetting

See a doctor if you have a high temperature, pain that won't go away, or a change in your usual pattern of passing urine. If you think your child may have a kidney infection, see a doctor immediately.

If there is blood in your urine, you should always see a doctor so the cause can be found.

A kidney infection needs prompt treatment with antibiotics. This helps relieve the symptoms and stops complications from developing.

The doctor can carry out some simple tests to help diagnose a kidney infection.

A kidney infection happens when bacteria infect your kidneys. The bacteria are usually a type called E. coli, which live in your bowel.

They get in through the opening of the urethra and travel upwards through your urinary tract. First they infect your bladder, and then your kidneys.

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

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

Women and children are most at risk of getting a kidney infection, and also other urinary tract infections (UTIs) such as cystitis.

In women, the urethra sits closer to the anus than it does in men, so bacteria from the anus can get into the urethra by accident. The female urethra is also much shorter than the male urethra (which runs through the penis). That makes it easier for bacteria to reach the bladder and then move up into the kidneys.

Other things can also raise your risk of a kidney infection, including:

• having a condition that blocks, or obstructs, your urinary tract, such as kidney stones or an enlarged prostate. Children with constipation can also be at higher risk
• being born with an abnormality in your urinary tract
• having a condition that stops you emptying your bladder fully, such as an injury to your spinal cord. This can let bacteria in your bladder multiply and spread
• having a weakened immune system, for example because of type 2 diabetes or as a side effect of chemotherapy
• having an infection of the prostate gland called prostatitis, because the infection can spread from the prostate gland into the kidneys
• having a urinary catheter (a thin, flexible tube put into your bladder to drain away urine)
• being female and sexually active, because sexual intercourse can irritate the urethra and let bacteria travel into your bladder
• being a man who has anal sex, because bacteria can travel up the urethra into the bladder
• being pregnant, because pregnancy can cause physical changes that slow the flow of urine out of your body and make it easier for bacteria to spread to the kidneys
• having undergone female genital mutilation (FGM), an illegal practice where a woman's genitals are deliberately cut or changed for cultural, religious and social reasons

To find out whether you have a kidney infection, your doctor will ask about your symptoms and your recent medical history. They will usually also check your general health by taking your temperature and measuring your blood pressure.

A urine test can help show whether you have a urinary tract infection (UTI). A small sample of your urine is taken and checked for bacteria.

You'll be given a container and told how to collect the urine. You can do this at the clinic or at home. If you do it at home, label the container, seal it in a plastic bag and keep it in the fridge. Ideally, hand it in to the clinic within four hours.

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

Before your doctor can be confident that you have a kidney infection, you need a positive urine test and certain symptoms as well, such as a fever or a pain in your side.

You may be referred to hospital for more tests if:

• your symptoms don't get better with antibiotics
• your symptoms suddenly get worse
• you have other symptoms that aren't usually linked with a kidney infection
• you're at risk of complications from a kidney infection

Children who keep getting UTIs will also be sent to hospital for more tests.

In these cases, scans can check your urinary tract for signs of problems. They may include:

• a computer tomography (CT) scan, where a scanner takes a series of X-rays and a computer puts them together into a detailed image of your urinary tract
• an ultrasound scan, which uses sound waves to build an image of the inside of your body
• an isotope scan, where a dye is injected into the bloodstream and a series of X-rays are taken

Most people with a kidney infection can be treated at home with a course of antibiotics, and sometimes painkillers as well.

See a doctor if you have a fever and ongoing pain in your tummy, lower back or genital area, or if you notice a change in your usual pattern of urination.

Any child with symptoms of a urinary tract infection (UTI) or kidney infection, including cystitis, should see a doctor or go to a hospital emergency department.

If you're being treated at home for a kidney infection, you'll usually get a course of antibiotic tablets or capsules. The course lasts between 7 and 14 days.

For most people, apart from pregnant women, the recommended antibiotics are ciprofloxacin or Co-amoxiclav. Other antibiotics may also be used. Ciprofloxacin commonly causes feeling sick and diarrhoea. Co-amoxiclav can make the contraceptive pill and contraceptive patches less effective, so you may need to use another form of contraception while you're on the course.

Pregnant women are given a different antibiotic called cefalexin, and the recommended course is 14 days.

You'll usually start to feel better quite soon after treatment begins, and you should feel completely better after about 2 weeks. If your symptoms show no sign of improvement 24 hours after treatment starts, contact your doctor for advice.

A painkiller such as paracetamol should help ease the pain and bring down a high temperature when you have a kidney infection.

Medicines called non-steroidal anti-inflammatories (NSAIDs), such as ibuprofen, aren't usually recommended for the pain of a kidney infection. They may raise the risk of further kidney problems.

If you have a kidney infection, try not to hover over the toilet seat when you pass urine. Hovering can mean your bladder doesn't empty fully.

Drink plenty of fluids too. This helps prevent dehydration and helps flush the bacteria out of your kidneys. Try to drink enough that you're passing pale-coloured urine often.

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

Your doctor may send you to hospital if you have an underlying problem with your urinary tract, because that makes you more likely to get kidney infections.

Doctors usually look into every man with a kidney infection more closely, simply because the condition is much rarer in men. Women are generally referred only if they have had 2 or more kidney infections. Most children with a kidney infection are treated in hospital.

You may also need hospital treatment if:

• you're severely dehydrated
• you're unable to swallow or keep down any fluids or medicines
• you have other 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 the age of 65
• 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 put on a drip so you can be given fluids to keep you hydrated. Antibiotics can be given through the drip as well.

You'll have regular blood and urine tests to check on your health and to see how well the antibiotics are fighting 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. Once the antibiotics through the drip are finished, treatment will usually switch to tablets or capsules.

Most kidney infections are treated successfully and don't cause any further problems, though a few people do develop complications.

Complications are rare. But you're more likely to get them if you:

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

A kidney abscess is a rare but serious complication of a kidney infection. Pus builds up inside the tissue of the kidney. You're thought to be most at risk if you have diabetes.

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

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

A kidney abscess can be serious because the bacteria inside it can spread to other parts of your body, such as your bloodstream or lungs, and this can be fatal.

Smaller abscesses can usually be treated with antibiotics given through a drip. Larger abscesses usually need surgery, where the pus is drained out using a needle that's inserted into the kidney.

Blood poisoning (also called sepsis) is another rare complication of a kidney infection, but it can be fatal. It happens when bacteria spread from the kidneys into the bloodstream. Once the bacteria are in your blood, the infection can reach any part of your body, including all of the major organs.

If you have a kidney infection, these are the symptoms of blood poisoning to watch for:

• low blood pressure, which makes you feel dizzy when you stand up
• confusion or disorientation
• excessive sweating
• uncontrollable shaking or shivering
• high temperature or lower body temperature than usual (under 36C, or 96.8F)
• pale skin
• rapid heartbeat
• breathlessness

Blood poisoning is a medical emergency. It usually means you will need to be admitted to a hospital intensive care unit (ICU) while antibiotics are used to fight the infection.

If you're taking certain medicines for diabetes, such as metformin, or ACE (angiotensin-converting enzyme) inhibitors, your doctor may stop them for a while until you recover. This is because they can cause kidney damage during an episode of blood poisoning.

Another complication of a kidney infection is rare, but it can be fatal. It's called emphysematous pyelonephritis (EPN).

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

Doctors don't know the exact cause of EPN, but almost all cases are in people with diabetes.

The usual treatment is emergency surgery to remove some, or all, of the affected kidney. You can still live a full and active life with only one kidney.

In very rare cases, a kidney infection can damage the kidneys so badly that they stop working properly. This is called kidney failure. It can be fatal, but it can be treated with dialysis or a kidney transplant.

A kidney infection can sometimes lead to other problems too. These include high blood pressure (hypertension), and in pregnancy it can bring on premature labour or birth.

The best way to prevent a kidney infection is to keep bacteria out of your bladder and urethra. The self-help tips below show you how to do this.

Drink plenty of liquids, especially water. It helps wash bacteria out of your bladder and urinary tract, which matters if you have a kidney infection.

Cranberry juice or cranberry extracts may also help prevent urinary tract infections (UTIs). But don't take them if you're on warfarin, a medicine used to prevent blood clots. Cranberry juice can make warfarin's effects stronger, and that raises the risk of excessive bleeding.

To help keep bacteria out of your urinary tract, a few simple habits can make a difference:

• 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
• wash your genitals every day and before having sex, to keep up good hygiene
• 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

Constipation can make a urinary tract infection (UTI) more likely, so it's best to treat it early.

These are the recommended treatments for constipation:

• increasing the fibre in your diet to 20g to 30g a day
• using a mild laxative for a short time
• drinking plenty of fluids

See a doctor if your symptoms don't get better after 14 days (or after 7 days for children with constipation).

If you keep getting UTIs (more than 3 a year is considered high), avoid spermicide-coated condoms or diaphragms. Spermicide can stimulate the production of bacteria.

Stick to lubricated condoms without spermicide. Unlubricated ones can irritate the urethra and make it more vulnerable to infection.