Hopkins 24/7

Back to ABC News

This Thursday at 10/9c

This content requires javascript and flash player version 8.

Johns Hopkins Symptoms and Remedies

Johns Hopkins Medicine

Close Article Browser

Kidney Infection Pyelonephritis

Most urinary tract infections remain confined to the urethra or bladder, but sometimes an infection ascends the ureters to involve the kidneys.

What is it?

Pyelonephritis is an infection of the kidneys, most often caused by bacteria. The kidneys filter waste products from the blood and produce urine, which passes to the bladder via the ureters (see illustration). The bladder stores urine, which leaves the body via the urethra. Normally, urine is sterile; it contains no bacteria or other microorganisms. But bacteria may enter the urethra and travel back up the urine stream to the kidneys, causing an infection. (In most cases, these are bacteria that normally inhabit the anal area with no ill effect.) Bacteria may also travel to the kidneys from infections elsewhere in the body via the bloodstream. Acute pyelonephritis may resolve without treatment, but it also responds well to antibiotics. However, recurrent or persistent kidney infection, known as chronic pyelonephritis—while rare and usually associated with stones or other abnormalities of the urinary system—may lead to scarring of the kidneys and, in severe cases, kidney failure. Kidney infections are more common in women, because the urethra is considerably shorter and so provides less of a barrier to bacteria.

What Causes It?

  • Most often, pyelonephritis is caused by a bacterial infection; a fungal infection may also rarely be a cause.
  • Risk is associated with kidney stones, bladder tumors, enlargement of the prostate, obstructive lesions of the urinary tract, venereal disease, diabetes mellitus, or the use of a urinary catheter.
  • In women, the risk of kidney infection increases with pregnancy and sexual activity.

Prevention

  • Women should practice careful hygiene. After using the toilet, wipe from front to back to avoid spreading fecal bacteria to the urethra.
  • Drink plenty of fluids to stay hydrated.

Diagnosis

  • Patient history and physical examination.
  • Urine sample for culture and microscopic analysis.

How to Treat It

  • Take over-the-counter pain relievers to reduce fever and discomfort, and get sufficient bed rest.
  • Drink eight or more glasses of water a day.
  • Antibiotics are often prescribed.
  • Surgery may be needed if a urinary tract abnormality or obstruction causes recurrent pyelonephritis.

When to Call a Doctor

  • Call a doctor immediately if you develop symptoms of a kidney infection.