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Kidney Infections: Know the Symptoms to Treat them on Time
Kidney Infections: Know the Symptoms to Treat them on Time
08 Sep 2023

Kidney Infections: Know the Symptoms to Treat them on Time

A kidney infection, or pyelonephritis, is a painful condition resulting from bacteria travelling from the bladder to one or both kidneys. This condition is more serious than cystitis, a common condition affecting the bladder that makes urinating painful.

With immediate and effective treatment, a kidney infection will not be life-threatening but will cause illness. If a kidney infection remains untreated, it can worsen, causing permanent kidney damage.

The symptoms of a kidney infection often occur within a few hours. It may cause fever, sickness, shivers, and pain in the side or back.

Symptoms of kidney infections

Symptoms of kidney infections seem to develop quickly within a few hours or days. Some of these include:

  • Chills or shivering
  • Diarrhoea
  • Feeling tired or weak
  • High temperature (up to 103.1oF or 39.5oC)
  • Discomfort or pain in the side, around the genitals or lower back
  • Loss of appetite
  • Being sick or feeling sick

Other symptoms may also occur if you have urethritis (urethral infection) or cystitis. These additional symptoms include:

  • Pain in the lower abdomen
  • Blood in the urine
  • Feeling unable to urinate fully
  • Burning sensation or pain during urination
  • Need to urinate urgently or frequently
  • Foul or cloudy-smelling urine

Children who experience a kidney infection may also have the following additional symptoms.

  • Irritability
  • A lack of energy
  • Bedwetting
  • Abdominal pain
  • Poor feeding and vomiting
  • The yellowing of the skin and whites of the eyes (jaundice)
  • Poor growth rate
  • Foul-smelling urine

Causes of kidney infections

A kidney infection occurs when bacteria enter and infect the kidneys. The bacteria, known as E. coli, live in the bowel.

The bacteria pass through the urethral opening and move upwards through the urinary tract. It first infects the bladder then the kidneys. The bacteria can enter the urinary tract by spreading from the anus to the urethra. It may occur when you wipe your bottom after using the toilet, and the contaminated toilet paper touches your genitals, and also during sex.

A kidney infection can also occur if fungi or bacteria infect the skin, and this infection spreads through the bloodstream to the kidneys, but this rarely occurs. However, a kidney infection usually affects only people with a weakened immune system.

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Who is likely to get a kidney infection?

Children and women are at a higher risk of developing a kidney infection, including other urinary tract infections (UTIs) like cystitis.

The urethra is closer to the anus in women than men, making it easier for bacteria from the anus to enter the urethra. Another reason for the increased risk of a kidney infection in women than men is the shorter female urethra than the male urethra, which runs through the penis, making it easier for bacteria to reach the bladder and enter the kidneys.

Other risk factors for developing kidney infection

  • Being born with a urinary tract abnormality
  • Having a condition that obstructs or blocks the urinary tract, including kidney stones or an enlarged prostate, including children with constipation.
  • Having a condition that prevents fully emptying the bladder, such as an injury to the spinal cord. This can allow bacteria to enter the bladder, multiply and spread.
  • Having a prostate gland infection called prostatitis – it can spread from the prostate glands to the kidneys.
  • Having a weakened immune system – for example, a side effect of chemotherapy or type II diabetes
  • Being a man who engages anal sex – bacteria can move into the urethra and the bladder.
  • Being a sexually active female – sexual intercourse can irritate the urethra, allowing bacteria to travel into the bladder.
  • Having a urinary catheter (a thin, flexible tube) inserted into the bladder to drain urine
  • Having undergone female genital mutilation – FGM is an illegal practice involving deliberate cutting or changing of the female genitals for religious, social and cultural reasons.
  • Being pregnant – can cause physical changes that slow down urine flow out of the body, making the spread of bacteria to the kidneys easier.

Risk factors for kidney infections

Anyone can have a kidney infection, but bladder infections are more common in women than men, so more women get kidney infections.

The urethra in females is shorter than in men and closer to their anus and vagina, meaning easier access for viruses and bacteria into the woman’s urethra. When bacteria enter the urethra, it can travel easily into the bladder and spread to the kidneys.

Pregnant women have a higher risk of bladder infections due to hormonal changes and the baby putting pressure on the mother’s bladder and urethra, which slows urine flow.

Any urinary tract problem that prevents urine from flowing as it should can increase the risk of a kidney infection. These include:

  • A problem in the urinary tract structure, like a pinched urethra
  • Conditions that prevent the bladder from fully emptying
  • An obstruction in the urinary tract, like an enlarged prostate or a kidney stone
  • Vesicoureteral reflux (VUX) – This is when urine flows backwards from the bladder towards the kidneys

You are likely to get a kidney infection if you have:

  • A urinary catheter inserted in the bladder through the urethra to drain urine
  • A prostate infection called prostatitis
  • Nerve damage in the bladder
  • A weakened immune system, which may result from type II diabetes

Diagnosing kidney infections

You need to consult your doctor about your medical history and symptoms to know if you have a kidney infection. The doctor will likely assess your general health by measuring your blood pressure and taking your temperature.

Urine Test

A urine test can determine the presence of a urinary tract infection (UTI). This test involves taking a small urine sample and checking if it contains bacteria. Your provider will give you a container and tell you how to collect the urine.

You can do this at the GP surgery or home. If you collect your urine sample at home, ensure you label the container, seal it in a plastic bag and store it in your fridge. You should submit it at the surgery within four hours.

A urine test cannot diagnose if your infection is in your kidney or another part of your urinary tract, like your bladder. You will need a positive urine test and certain symptoms like pain in your side or fever for your GP to diagnose a kidney infection.

Hospital scans

Your healthcare provider may refer you to a hospital for further testing if:

  • Your symptoms suddenly worsen
  • Your symptoms do not respond to treatment with antibiotics
  • You are at risk of complications of a kidney infection
  • You experience additional symptoms that are unrelated to a kidney infection

Children with recurrent UTIs may also need further testing at the hospital. In these cases, scans can check for signs of urinary tract problems. These scans may include:

  • An isotope scan – the healthcare professional will infect a dye into your bloodstream and take a series of X-rays
  • A computer tomography (CT) scan – a scanner takes several X-rays and computer assembles them into a detailed image of the urinary tract.
  • An ultrasound scan – This scan uses sound waves to build an image of the inner parts of the body

Duration of kidney infections

Kidney infections usually start as urinary tract infections (UTIs), affecting the bladder. There is no specific time for UTI to spread from the bladder to the kidneys. A kidney infection can’t resolve on its own.

Untreated kidney infection can lead to a severe infection, potentially causing sepsis or a chronic, recurrent infection.

You may feel better within 2 – 3 days of taking antibiotics. However, ensure you continue taking your medication and complete your treatment course.

Treatment for mild infections can take 7 – 14 days, with symptoms taking a week or longer to resolve with treatment.

A complicated or severe kidney infection may take longer to treat, depending on the extent of the infection and the complications it causes.

Complications of kidney infections

Most cases of kidney infections are treatable and cause no complications, but some people develop further health issues. Complications from a kidney infection rarely occur but are more likely to occur in:

  • Children
  • People over 65 years
  • Pregnant women
  • People with chronic kidney disease, sickle cell anaemia and diabetes
  • People with a kidney transplant (particularly in the first three months after the kidney transplant)
  • People with a weakened immune system

Some complications of kidney infections include:

Kidney abscess

A kidney abscess rarely occurs. It is a serious complication of a kidney infection where pus accumulates in the kidney tissue. People with diabetes are more at risk of developing a kidney abscess. Kidney abscess symptoms are similar to a kidney infection. They include:

  • Loss of appetite
  • Chills
  • A high temperature of 38oC (100.4oF) or above
  • Pain when passing urine
  • Abdominal pain

A kidney abscess is a potentially serious issue because bacteria in the abscess can spread to other body parts, such as the lungs or bloodstream, and is potentially fatal.

Small abscesses are treatable with antibiotics administered through a drip. Surgery may be necessary for larger abscesses. The procedure will involve draining the pus from the abscess using a needle inserted into the kidney.

Blood poisoning

Blood poisoning, also known as sepsis, is another rare complication but potentially life-threatening. It occurs when bacteria spread from the kidneys into the bloodstream. When bacteria enter your blood, the infection can easily spread to any body part, including your major organs.

The symptoms of blood poisoning from a kidney infection may include:

  • Disorientation or confusion
  • Low blood pressure that causes dizziness when standing up
  • Lower or higher body temperature
  • Excessive sweating
  • Uncontrollable shivering or shaking
  • Breathlessness
  • Rapid heartbeat
  • Pale skin

Blood poisoning requires immediate medical attention, involving hospital intensive care (ICU) admission and administering antibiotics to fight the infection.

If you take certain diabetes medications like angiotensin-converting enzyme (ACE) inhibitors or metformin, you may need to stop them temporarily until you recover. These medications can cause kidney damage during a blood poisoning episode.

Severe infection

Severe infection, known as emphysematous pyelonephritis, is also rare but potentially fatal. In EPN, the kidney tissues get destroyed rapidly, and the bacteria that causes the infection release a toxic gas that accumulates in the kidneys.

The exact cause of EPN is still unclear, but most people who experience it have diabetes. Treatment often involves emergency surgery to remove some parts or all of the affected kidney. You can live an active and full life with only one kidney.

Kidney failure

In rare cases, the kidney infection may result in severe kidney damage that causes kidney failure. Kidney failure is potentially life-threatening but can be treated with a kidney transplant or dialysis.

Other problems

A kidney infection may also cause complications such as premature birth, labour, or high blood pressure (hypertension).

Treatment for kidney infections

Most cases of kidney infections are treatable at home with a course of antibiotics and painkillers. Ensure you visit your GP if you experience persistent tummy, genital or lower back pain, fever or any changes in your urination pattern.

Children with kidney infection or urinary tract infection (UTI) symptoms, including cystitis, need to see a GP.

Concerned about any of the issues raised in this article? It's well worth undergoing a full body health screening to check for underlying issues, with 4 GP appointments included in all Advanced and Elite MOTS throughout 2023.



If you are getting treatment at home, your provider will prescribe a course of antibiotic capsules or tablets that lasts 7 – 14 days.

Most people, excluding pregnant women, take co-amociclave or ciprofloxacin. Other antibiotics are also effective.

The common side effects of ciprofloxacin include diarrhoea and feeling sick. Co-amoxiclav can make contraceptive patches and pills less effective, so another form of contraception may be necessary during this treatment.

Doctors usually prescribe a 14-day course of antibiotics known as cephalexin for pregnant women.

You will likely start feeling better after treatment starts and should feel completely fine after about two weeks. If your symptoms don’t improve after 24 hours of treatment, contact your doctor.


Painkillers like paracetamol can relieve your pain symptoms and a high temperature. However, avoid taking non-steroidal anti-inflammatory (NSAIDs) such as ibuprofen to relieve pain from a kidney infection. These medications increase the risk of kidney problems.

Self-help tips

Avoid remaining on the toilet seat for too long when you go to the loo if you have a kidney infection. Ensure you drink lots of fluids to prevent dehydration and flush out the bacteria from your kidney. Drink enough fluid so you can frequently pass pale-coloured urine.

Resting is also important. A kidney infection is usually physically draining, even if you are usually strong and healthy. It may take about two weeks to be healthy enough to resume work.

Treatment at the hospital

Your doctor may refer you to a hospital if you have any underlying urinary tract problem that increases your risk for kidney infections.

Men with kidney infections usually need further investigation because the condition rarely occurs in men. Only women who have had two or more kidney infections get a referral to the hospital. Most children with kidney infections undergo treatment in the hospital.

Treatment in the hospital may be necessary if:

  • You have additional symptoms suggesting blood poisoning, such as losing consciousness and a rapid heartbeat.
  • You are severely dehydrated
  • You cannot keep down or swallow any medications or fluids
  • You have diabetes
  • You have an underlying condition affecting how your kidneys work, such as chronic kidney disease or polycystic kidney disease.
  • You are over 65 years old.
  • You are pregnant and have a high temperature.
  • You have a foreign substance in your urinary tract, like a urinary catheter or kidney stone.
  • You have a weakened immune system.
  • Your symptoms do not improve within 24 hours after starting treatment with antibiotics.
  • Your general health is poor or particularly frail.

If you are admitted to the hospital for a kidney infection, you may likely get a drip to supply fluids to help prevent dehydration. The drip may also contain antibiotics. You will have regular urine and blood tests to monitor your health and the effectiveness of the antibiotics.

Most people respond well to the treatment; if there are no complications, they can leave the hospital within 3 – 7 days. The treatment will switch to capsules or tablets after your drips with antibiotics are stopped.

Complementary and alternative therapies

There are no effective complementary or alternative therapies or methods to cure a kidney infection. However, some ways are available to increase your comfort during antibiotic treatment. This includes placing a heating pad on your back, side or abdomen to ease pain in the affected areas.

Drinking plenty of liquid can help flush out the bacteria that cause the infection from your system, and resting is also important to help you recover.

Preventing kidney infections

The best way to prevent kidney infections is to keep your urethra and bladder free from the infection-causing bacteria.

The following self-help tips can help you achieve this.

Drink lots of fluids.

Drinking lots of fluids, particularly water, will help flush bacteria from your urinary tract and bladder. You can also prevent urinary tract infections (UTIs) by taking cranberry extracts or drinking cranberry juice.

However, avoid taking cranberry extracts or juice if you take warfarin, a medicine for preventing blood clots. Cranberry juice can make warfarin more potent, increasing the risk of excessive bleeding.

Toilet tips

The following will help prevent bacteria from entering your urinary tract.

  • Go to the toilet immediately if you feel the urge to urinate instead of holding your urine in
  • Wipe from front to back after using the toilet.
  • If you are a woman, avoid remaining on the toilet seat for too long, as this position can leave urine in your bladder.
  • Empty your bladder after sex
  • Practice good hygiene by washing your genitals daily and before sex

Treat constipation

Constipation may increase the risk of a urinary tract infection, so treating it as soon as possible is important. The recommended constipation treatments include:

  • Using a mild laxative for a short while
  • Increase your daily fibre intake to 20 – 30g
  • Drinking lots of liquid

Visit your doctor if your symptoms do not improve after 14 days, but after seven days for children.

Be careful with contraceptives.

If you keep getting UTI more than three times a year, avoid using diaphragms or spermicide-coated condoms, as spermicide can cause bacteria production.

Opt for lubricated condoms without spermicide because unlubricated condoms may irritate the urethra, increasing the risk of infection.

When should I see my doctor?

Visit your doctor if you have persistent genital, tummy or lower back pain and a fever or if you notice changes in your usual urination pattern.

Most kidney infections need immediate treatment with antibiotics to prevent the infection from spreading to the bloodstream or damaging the kidneys. Painkillers may also be necessary to alleviate any pain.

You should feel better after your course of antibiotics, which usually lasts two weeks. In rare cases, the kidney infection may result in further problems, such as kidney abscess or blood poisoning (sepsis).

If you have symptoms of a kidney infection, visit our private GP London to see a general practitioner for your condition.

You can contact us at 020 7499 1991 to book an appointment with our doctor or for more information on kidney infections, including ways to prevent this infection.

Frequently asked questions

What will happen if I do not treat a kidney infection?

Untreated kidney infections can damage the kidneys and cause long-term health issues. In rare cases, kidney infections can cause kidney disease, kidney failure or high blood pressure. If the kidney infection enters the bloodstream, it may result in a serious problem known as sepsis.

Can the kidney infection-causing bacteria become resistant to antibiotics?

Yes, it can. The bacteria can become resistant to only some antibiotics. You will have both blood and urine cultures before starting medications. With these tests, your healthcare provider can know the medicine that will be most effective for you.

How can I prevent kidney infections?

Women should wipe from front to back after using the toilet. This will prevent bacteria from moving into the urethra opening. Urinating after having sex may also help remove bacteria in the urethra. Some contraceptives, excluding spermicidal foam or diaphragms, may help.

What if I am pregnant?

UTIs during pregnancy are dangerous to both the baby and the mother. The infection requires immediate treatment, and safe medicines are available for pregnant women to treat UTIs.