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Kidneys and adrenal glands

Alternative Names
kidney infection

Pyelonephritis is an infection of the kidneys or the ureters. The ureters are small tubes that carry urine from the kidneys to the bladder. Pyelonephritis may come on suddenly or it may be a long-term problem.

What is going on in the body?
Escherichia coli is a bacteria that is normally found in the large intestine. It causes about 90 percent of kidney infections. These infections usually spread from the genital area through the ureters to the bladder. In a healthy urinary tract, the infection is prevented from going to the kidneys by the flow of urine, which washes organisms out. When bacteria enter the usually "germ-free" urinary tract, they can cause pyelonephritis.

What are the signs and symptoms of the infection?
Symptoms of pyelonephritis may include:
  • sudden fever, often over 38 to 39 degrees Celsius
  • chills
  • severe pain and tenderness in the sides, abdomen, or back
  • tenderness when the kidneys are pressed
  • warm, moist, flushed skin
  • frequent urination
  • difficulty starting a stream of urine
  • pain or burning sensation when urinating
  • cloudy or abnormally coloured urine
  • nausea
  • vomiting
  • diarrhoea
  • fatigue
  • mental changes or confusion, as the infection progresses
What are the causes and risks of the infection?
Pyelonephritis is usually caused by bacteria entering the kidneys from the bladder. The most common causes of this bacteria reaching the bladder include:
  • use of a urinary catheter for draining urine from the bladder
  • surgery on the urinary tract
  • diagnostic testing that uses a scope to enter the urinary tract, such as cystoscopy
  • conditions that block the way the urine flows through the urinary tract, including uterine fibroids, benign prostatic hyperplasia, kidney stones, and pregnancy
  • conditions that make a person more prone to infection, such as diabetes
  • a problem with the urinary tract that is present at birth
What can be done to prevent the infection?
There are many ways to prevent the spread of bacteria in the urinary tract. These include:
  • wiping from the front to the back of the genital area, especially after a bowel movement
  • drinking plenty of fluids
  • emptying the bladder at least every 3 to 4 hours and after sexual intercourse
  • avoiding bubble baths
  • avoiding tight fitting clothes
  • wearing cotton underwear
How is the infection diagnosed?
Diagnosis requires a urinalysis, or urine test. A urine culture is also done on a urine sample to see if there are bacteria in the urine. Typical findings include pus, white blood cells, and blood in the urine. X-rays are also helpful in the diagnosis.

What are the long-term effects of the infection?
Untreated pyelonephritis can lead to:
  • chronic kidney infections
  • permanent kidney damage
  • scarring of the kidneys
  • sepsis, or blood poisoning
What are the risks to others?
Pyelonephritis is not contagious. Certain conditions that increase a person's risk of kidney infection, such as sexually transmitted disease, may be very contagious.

What are the treatments for the infection?
A person is usually given antibiotics as soon as the diagnosis of a kidney infection seems likely. The most common antibiotics prescribed include:
  • sulphur medications
  • cephalosporins, such as cephaclor or cephalexin
  • trimethoprim-sulfamethoxazole
A person with a severe infection may need to be hospitalised. Sometimes surgery is needed to correct a physical problem with the urinary tract.

What are the side effects of the treatments?
The side effects of antibiotics include stomach upset, rash, or allergic reaction. The side effects of surgery include bleeding, infection, or an allergic reaction to anaesthesia.

What happens after treatment for the infection?
It is very important for the person to complete the full course of antibiotics. In some cases, a low dose of an antibiotic may be prescribed for a person to take continually to keep the infection from coming back.

Sometimes a person has many episodes of pyelonephritis in a short time period. Further testing may need to be done to rule out kidney disease or urinary tract abnormalities. Common tests include:
  • ultrasound of the kidney and bladder
  • a voiding cystourethrogram, or VCUG, in which a liquid is put into the bladder through a catheter, or tube, inserted through the urethra. An x-ray then follows the liquid through the bladder and urethra. This test can reveal abnormalities of the inside of the urethra and bladder.
  • intravenous pyelogram, which examines the whole urinary tract. A liquid is injected through a tube inserted into a vein. An x-ray then follows the liquid as it flows through the urinary tract. This test may reveal blockages in the tract.
  • a nuclear scan, in which radioactive materials are injected into a vein. This test shows how the kidneys work, how the kidneys are shaped, and how urine drains from the kidneys.
How is the infection monitored?
Follow-up urine cultures need to be done several weeks after the person is finished taking the antibiotics. This is important to make sure that the treatment has been effective. Untreated pyelonephritis can lead to very serious kidney damage. Any new or worsening symptoms should be reported to the doctor.

Author: Eileen McLaughlin, RN, BSN
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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