Overview

A kidney infection is a type of urinary tract infection (UTI). A kidney infection may begin in the tube that carries urine from the body (urethra) or in the bladder. The infection can travel to one or both kidneys. A kidney infection is also called pyelonephritis.

A kidney infection needs prompt medical treatment. If not treated properly, an infection can cause lasting damage to the kidneys. Or the bacteria can spread to the bloodstream and cause a dangerous infection.

Kidney infection treatment often includes antibiotics, which might be given in the hospital.

Symptoms

Symptoms of a kidney infection might include:

  • Fever
  • Chills
  • A burning feeling or pain when urinating
  • Having to urinate often
  • A strong, lasting urge to urinate
  • Back, side or groin pain
  • Nausea and vomiting
  • Pus or blood in the urine
  • Urine that smells bad or is cloudy
  • Belly pain

When to see a doctor

Make an appointment with your health care provider if you have symptoms of a kidney infection. Also see your provider if you're being treated for a UTI but your symptoms aren't getting better.

A severe kidney infection can lead to dangerous complications. They may include blood poisoning, damage to the body's tissues or death. Seek medical care right away if you have kidney infection symptoms and bloody urine or nausea and vomiting.

Causes

Bacteria that enter the urinary tract through the urethra can multiply and travel to your kidneys. This is the most common cause of kidney infections.

Bacteria from an infection in another part of the body also can spread through the bloodstream to the kidneys. In rare cases, an artificial joint or heart valve that becomes infected can cause a kidney infection.

Rarely, a kidney infection happens after kidney surgery.

Risk factors

Factors that increase the risk of a kidney infection include:

  • Being female. The urethra is shorter in women than in men. That makes it easier for bacteria to travel from outside the body to the bladder. The urethra being close to the vagina and anus also makes it easier for bacteria to enter the bladder.

    Once in the bladder, an infection can spread to the kidneys. Pregnant women are at even higher risk of a kidney infection.

  • Having a urinary tract blockage. Anything that slows the flow of urine or makes it harder to fully empty the bladder can raise the risk of a kidney infection. This includes a kidney stone, a narrowed urethra or an enlarged prostate gland.
  • Having a weakened immune system. Medical conditions such as diabetes and HIV can weaken the immune system. Certain medicines also can lower immunity. These include drugs taken after an organ transplant that help prevent rejection.
  • Having damage to nerves around the bladder. Nerve or spinal cord damage can block the feeling of a bladder infection. That can make it hard to know when an infection travels to a kidney.
  • Using a urinary catheter. Urinary catheters are tubes used to drain urine from the bladder. Catheters are sometimes used after a surgical procedure or diagnostic test. They're also used in people who are confined to a bed.
  • Having a condition that causes urine to flow the wrong way. In vesicoureteral reflux, small amounts of urine flow from the bladder back into the tubes that connect the bladder and kidneys. People with this condition are at higher risk of kidney infections when they're kids and when they become adults.

Complications

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. The kidneys filter waste from blood and return the filtered blood to the rest of the body. A kidney infection can cause bacteria to spread through the bloodstream.
  • Pregnancy complications. A kidney infection that occurs during pregnancy can increase the risk of having a baby with a low birth weight.

Prevention

Reduce your risk of kidney infection by taking steps to prevent urinary tract infections. Women in particular may lower the risk of urinary tract infections if they:

  • Drink fluids, especially water. Fluids can help remove bacteria from the body when you urinate.
  • Urinate as soon as you need to. Don't delay urinating when you feel the urge.
  • Empty the bladder after sexual intercourse. Urinating as soon as possible after sex helps clear bacteria from the urethra. This lowers the risk of infection.
  • Wipe carefully. Wipe from front to back after urinating and after a bowel movement. This helps prevent bacteria from spreading to the urethra.
  • Avoid using products in the genital area. Deodorant sprays in the genital area or douches can be irritating.
By Mayo Clinic Staff