Kidney infection

Kidney infection developed in a bowel-dwelling germ called E. coli, in most cases. This germ enters the urethra (the tube that carries urine out of the body) and travels upward, first infecting the bladder and then the kidneys.

What causes a kidney infection

A kidney infection happens when bacteria, usually the E. coli type that normally lives in your bowel, infects your kidneys. The bacteria enter through the opening of the urethra and move upward through your urinary tract, first infecting your bladder and then your kidneys.

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

In rare cases, a kidney infection develops when bacteria or fungi infect the skin and spread through the bloodstream into the kidney. However, this type usually only occurs in people with weakened immune systems.

Kidney infections are relatively rare. It is estimated that about one in every 830 people develops a kidney infection each year. They can happen at any age but are much more common in women, who are 6 times more likely than men to get one. This is because a woman's urethra is shorter and closer to the anus, making it easier for bacteria from the anus to enter the urethra and travel up to the bladder and kidneys.

Younger women are most at risk because they tend to be more sexually active, and frequent sex increases the chances of getting a kidney infection. Younger children are also vulnerable, since they may be born with an abnormality of the urinary tract or have a condition called vesico-ureteric reflux, where urine flows backward from the bladder up to the kidneys.

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

Other factors can also put you more at risk of developing 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 increased risk
• being born with an abnormality in your urinary tract
• having a condition that prevents you from emptying your bladder fully, such as an injury to your spinal cord, which can allow bacteria in your bladder to multiply and spread
• having a weakened immune system, for example due to type 2 diabetes or as a side effect of chemotherapy
• having an infection of the prostate gland called prostatitis, where the infection can spread from the prostate gland into the kidneys
• having a urinary catheter (a thin, flexible tube inserted into your bladder to drain away urine)
• being female and sexually active, since sexual intercourse can irritate the urethra and allow bacteria to travel into your bladder
• being a man who has anal sex, which allows bacteria to travel up the urethra into the bladder
• being pregnant, which 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 in which a woman's genitals are deliberately cut or altered for cultural, religious and social reasons

To work out if you have a kidney infection, your GP will ask about your symptoms and your recent medical history.

They'll usually also check your general health by taking your temperature and measuring your blood pressure.

Urine test

A urine test can help show whether you have a urinary tract infection (UTI). It involves taking a small sample of your urine and checking it for bacteria.

You'll be given a container and told how to collect the urine, which you can do at the surgery 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 surgery within four hours.

A urine test on its own can't show whether an infection, if you have one, is in your kidneys or elsewhere in your urinary system, such as your bladder.

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

Hospital scans

You may be referred to hospital for further testing if:

• your symptoms don't respond to antibiotic treatment
• your symptoms suddenly get worse
• you have additional symptoms that aren't usually linked to a kidney infection
• you're at risk of complications from a kidney infection

Children with repeated UTIs will also be referred to hospital for further testing.

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

• a CT (computer tomography) scan, where a scanner takes a series of X-rays that a computer assembles into a detailed image of your urinary tract
• an ultrasound scan, which uses sound waves to build a picture 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

Read more about treating a kidney infection.

Treating kidney infections

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

See your GP if you have a fever and persistent tummy, lower back or genital pain, or if you notice a change to your usual pattern of urination.

All children with symptoms of a urinary tract infection (UTI) or kidney infection, including cystitis, should see their GP or out-of-hours emergency service.

Medication

Antibiotics

If you’re being treated at home, you’ll usually be prescribed a course of antibiotic tablets or capsules that lasts between 7 and 14 days.

For most people – apart from pregnant women – antibiotics called ciprofloxacin or Co-amoxiclav are recommended. However, other antibiotics may also be used.

Common side effects of ciprofloxacin include 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 during the course of treatment.

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

Usually, you’ll start to feel better quite soon after treatment starts 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 GP for advice.

Painkillers

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

However, non-steroidal anti-inflammatories (NSAIDs) such as ibuprofen aren’t usually recommended to relieve pain during a kidney infection. This is because they may increase the risk of further kidney problems.

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.

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

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

Your GP may refer you to hospital if you have an underlying problem with your urinary tract, which makes you vulnerable to kidney infections.

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 2 or more kidney infections tend to be referred. Most children with a kidney infection will be treated in hospital.

Hospital treatment may also 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 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 attached to a drip so 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 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. Treatment will usually switch to tablets or capsules after you stop receiving antibiotics through a drip.

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 20g to 30g of fibre a day
• using a mild laxative on a short-term basis
• drinking plenty of fluids

See your GP if your symptoms don’t improve after 14 days (or 7 days for children with constipation).

Read more about treating constipation

Be careful with contraceptives

If you keep getting UTIs (more than 3 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 and make it more vulnerable to infection.

Don’t include personal information e.g. name, location or any personal health conditions.

Can a kidney infection be prevented?

You can lower your chances of getting a kidney infection by keeping bacteria out of your bladder and urethra. This means drinking plenty of fluids, keeping your genitals clean, and treating any constipation promptly.

Read more about preventing a kidney infection below.

Preventing kidney infections

The best way to prevent a kidney infection is to keep your bladder and urethra free from bacteria. The self-help tips below explain how you can do this.

Drink plenty of liquids

Drinking plenty of liquids, especially water, helps wash bacteria out of your bladder and urinary tract.

Drinking cranberry juice or taking cranberry extracts may also help prevent urinary tract infections (UTIs). However, avoid cranberry juice or extracts if you're taking warfarin, a medicine used to prevent blood clots. Cranberry juice can make warfarin's effects stronger, which raises the risk of excessive bleeding.

Toilet habits

To help keep your urinary tract free from bacteria:

• go to the toilet as soon as you feel the urge to urinate, rather than holding it in
• wipe from front to back after using the toilet
• practice good hygiene by washing your genitals daily and before having sex
• empty your bladder after having sex
• if you're a woman, avoid "hovering" over a toilet seat, since this position can often leave urine behind in the bladder

Most kidney infections clear up completely with treatment, but a few people go on to develop further problems.

Complications from a kidney infection are uncommon, but you have a higher chance of running into them if you:

• are a child
• are over 65 years old
• are pregnant
• have diabetes, chronic kidney disease or sickle cell anaemia
• have had a kidney transplant (especially in the first three months afterward)
• have a weakened immune system
• picked up the kidney infection while already in hospital

Kidney abscess

A kidney abscess is a rare but serious complication of a kidney infection, in which pus collects inside the kidney tissue. People with diabetes are thought to be at the highest risk of this.

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

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

Kidney abscesses can be serious because the bacteria inside them can spread to other parts of the body, such as the bloodstream or lungs, and this can be fatal. Smaller abscesses can usually be treated with antibiotics given through a drip. Larger ones usually need surgery, where a needle is inserted into the kidney to drain the pus out.

Blood poisoning

Blood poisoning, also called sepsis, is another rare but potentially fatal complication of a kidney infection. It happens when bacteria spread from the kidneys into the bloodstream, from where the infection can reach any part of the body, including the major organs.

In someone with a kidney infection, the signs of blood poisoning include:

• low blood pressure, which can make you feel dizzy on standing up
• confusion or disorientation
• heavy sweating
• uncontrollable shaking or shivering
• a high temperature, or a body temperature lower than usual (under 36C, or 96.8F)
• pale skin
• a rapid heartbeat
• breathlessness

Blood poisoning is a medical emergency and usually means being admitted to a hospital intensive care unit (ICU) while antibiotics are used to fight the infection. If you are on certain diabetes medicines, such as metformin, or on ACE inhibitors, these may be stopped for a while until you recover, since they can add to kidney damage during an episode of blood poisoning.

Severe infection

Another rare but potentially fatal complication is a condition known as emphysematous pyelonephritis, or EPN. In EPN, the kidney tissue is destroyed very quickly, and the bacteria causing the infection start releasing a toxic gas that builds up inside the kidney.

It is not entirely clear why EPN happens, but it is almost always seen in people with diabetes. Treatment usually means emergency surgery to remove part or all of the affected kidney. It is entirely possible to live a full, active life with just one kidney.

Kidney failure

In very rare cases, a kidney infection can damage the kidneys so severely that they stop working properly, a condition known as kidney failure. This can be life threatening, but it can be treated with dialysis or a kidney transplant.

Other problems

A kidney infection can sometimes lead to other complications too, such as high blood pressure or premature labour and birth.