kidney infection
kidney infection

Kidney infection, also known as renal infection or pyelonephritis, is a common type of urinary tract infection.

The main jobs of your kidneys are to clean the waste and remove extra water from your blood.

What is the urinary tract?

The urinary tract consists of:

  • The kidneys: The majority of humans have two kidneys, one on either side of the abdomen. Kidneys clear poisonous substances from the blood.
  • The ureters: Urine passes from the kidneys to the bladder through tubes called ureters. Each kidney has one ureter connecting it to the bladder.
  • The bladder: This is a hollow organ in the lower abdomen that stores urine.
  • The urethra: A tube that carries urine from the bladder to outside the body. In males, the urethra travels down the middle of the penis to an opening at the end. In females, the urethra runs from the bladder to just above the vaginal opening. The urethra in females is shorter than in males.
    Urinary tract
    Urinary tract


    Symptoms of kidney infection usually appear two days after infection. Your symptoms may vary, depending on your age. Common symptoms include:

    • pain in your abdomen, back, groin, or side
    • nausea or vomiting
    • frequent urination or the feeling that you have to urinate
    • burning or pain while urinating
    • pus or blood in your urine
    • bad-smelling or cloudy urine
    • chills
    • fever

    Children under 2 years old with a kidney infection may have only a high fever. People over 65 may only have problems like mental confusion and jumbled speech.

    If the infection is not treated promptly, symptoms could worsen, leading to sepsis. This can be life-threatening. Symptoms of sepsis include:

    • fever
    • chills
    • rapid breathing and heart rate
    • rash

       Causes of kidney infection

      A kidney infection usually happens when bacteria – often a type called E. coli – get into the tube that carries urine out of your body (urethra).

      The bacteria travel up to your bladder, causing cystitis, and then up into your kidneys.

      There are a number of ways in which the bacteria can achieve this:

      • Toilet hygiene: After going to the toilet and using toilet paper to clean the anus, there may be contact with the genitals, resulting in an infection getting through and working its way up to the kidneys. The infection could also enter via the anus. Bacteria occupy the colon and eventually cause a kidney infection.
      • Female physiology: Women are more vulnerable to bladder infections and ultimately kidney infections than men, because their urethra is shorter, making it easier for infections to reach parts of the urinary tract more quickly.
      • Urinary catheter: A urinary catheter is a tube that is inserted into the bladder through the urethra to drain out urine. Having a urinary catheter raises the risk of developing a urinary tract infection (UTI). This includes kidney infection.
      • Kidney stones: Individuals with kidney stones have a higher risk of developing kidney infection. Kidney stones are the result of a buildup of dissolved minerals on the inner lining of the kidneys.
      • Enlarged prostate: Males with an enlarged prostate have a higher risk of developing kidney infections.
      • Sexually active females: If sexual intercourse irritates the urethra there may be a higher risk of bacteria getting inside the urinary tract and eventually reaching the kidneys.
      • Weakened immune systems: Some patients with weakened immune systems may have a bacterial or fungal infection on their skin, which eventually gets into the bloodstream and attacks the kidneys.

        Risk factors

        Factors that increase your risk of a kidney infection include:

        • Having a urinary tract blockage. This includes anything that slows the flow of urine or reduces your ability to empty your bladder when urinating — including a kidney stone, something abnormal in your urinary tract’s structure or, in men, an enlarged prostate gland.
        • Having a weakened immune system. This includes medical conditions that impair your immune system, such as diabetes and HIV. Certain medications, such as drugs taken to prevent rejection of transplanted organs, have a similar effect.
        • Having damage to nerves around the bladder. Nerve or spinal cord damage can block the sensations of a bladder infection so that you’re unaware when it’s advancing to a kidney infection.
        • Using a urinary catheter for a time. Urinary catheters are tubes used to drain urine from the bladder. You might have a catheter placed during and after some surgical procedures and diagnostic tests. You might use one continuously if you’re confined to a bed.
        • Having a condition that causes urine to flow the wrong way. In vesicoureteral reflux, small amounts of urine flow from your bladder back up into your ureters and kidneys. People with this condition are at higher risk of kidney infection during childhood and adulthood.


        If left untreated, a kidney infection can lead to potentially serious complications, such as:

        • Kidney scarring. This can lead to chronic kidney disease, high blood pressure and kidney failure.
        • Blood poisoning (septicemia). Your kidneys filter waste from your blood and return your filtered blood to the rest of your body. Having a kidney infection can cause the bacteria to spread through your bloodstream.
        • Pregnancy complications. Women who develop a kidney infection during pregnancy may have an increased risk of delivering low birth weight babies.

        Being female. The urethra is shorter in women than it is in men, which makes it easier for bacteria to travel from outside the body to the bladder. The nearness of the urethra to the vagina and anus also creates more opportunities for bacteria to enter the bladder.



        Your doctor will ask you questions about your medical history and symptoms.

        They will also ask about any risk factors you might have and do a physical examination.

        Some of the tests the doctor may use include:

        • A rectal examination for males. This may be done to check whether the prostate is enlarged and blocking the bladder neck.
        • Urinalysis. A urine sample will be examined under a microscope for bacteria and also white blood cells, which your body produces to fight infection.
        • Urine culture. A urine sample will be cultured in the laboratory to determine the specific bacteria that grow.
        • ACT scan, MRI, or ultrasound test. These provide images of your kidneys.


          Reduce your risk of kidney infection by taking steps to prevent urinary tract infections.

          Women, in particular, may reduce their risk of urinary tract infections if they:

          • Drink fluids, especially water. Fluids can help remove bacteria from your body when you urinate.
          • Urinate as soon as you need to. Avoid delaying urination when you feel the urge to urinate.
          • Empty the bladder after intercourse. Urinating as soon as possible after intercourse helps clear bacteria from the urethra, reducing your risk of infection.
          • Wipe carefully. Wiping from front to back after urinating and after a bowel movement helps prevent bacteria from spreading to the urethra.
          • Avoid using feminine products in the genital area. Using products such as deodorant sprays in your genital area or douches can be irritating.


            Your treatment will depend on the severity of your kidney infection.

            If the infection is mild, oral antibiotics are the first line of treatment.

            Your doctor will prescribe antibiotic pills for you to take at home.

            The type of antibiotic may change once the results of your urine tests are known to something more specific to your bacterial infection.

            Usually you’ll need to continue taking antibiotics for two or more weeks.

            Your doctor may prescribe follow-up urine cultures after your treatment to make sure the infection is gone and has not returned. If necessary, you may get another course of antibiotics.

            For a more serious infection, your doctor may keep you in the hospital to receive intravenous antibiotics and intravenous fluids.

            Sometimes surgery may be necessary to correct a blockage or problematic shape in your urinary tract. This will help prevent new kidney infections.