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Pyelonephritis is an infection of the kidney and the ureters, the ducts that carry urine away from the kidney.

Urinary tract infection - complicated; Infection - kidney; Complicated urinary tract infection; Kidney infection

Pyelonephritis most often occurs as a result of urinary tract infection, particularly when there is occasional or persistent backflow of urine from the bladder into the ureters or an area called the kidney pelvis. See: Vesicoureteric reflux

Pyelonephritis can be sudden (acute) or long-term (chronic).

• Acute uncomplicated pyelonephritis is the sudden development of kidney inflammation.
• Chronic pyelonephritis is a long-standing infection that does not go away.

Pyelonephritis occurs much less often than a bladder infection, although a history of such an infection increases your risk. You're also at increased risk for a kidney infection if you have any of the following conditions:

• Backflow of urine into the ureters or kidney pelvis
• Kidney stones
• Ostructive uropathy
• Renal papillary necrosis

You are also more likely to get a kidney infection if you have a history of chronic or recurrent urinary tract infection, especially if the infection is caused by a particularly aggressive type of bacteria.

Acute pyelonephritis can be severe in the elderly and in people who are immunosuppressed (for example, those with cancer or AIDS).

• Back pain orflank pain
• Chills with shaking
• Severe abdominal pain (occurs occasionally)
• Fatigue
• Fever
  • Higher than 102 degrees Fahrenheit
  • Persists for more than 2 days
• General ill feeling
• Chills with shaking
• Mental changes or confusion*
• Skin changes
  • Flushed or reddened skin
  • Moist skin (diaphoresis)
  • Warm skin
• Urination problems
  • Blood in the urine
  • Cloudy or abnormal urine color
  • Foul or strong urine odor
  • Increased urinary frequency or urgency
  • Need to urinate at night (nocturia)
  • Painful urination
• Vomiting, nausea

* Mental changes or confusion may be the only signs of a urinary tract infection in the elderly.

A physical exam may show tenderness when the health care provider presses (palpates) the area of the kidney.

• Blood culture may show an infection.
• Urinalysis commonly reveals white or red blood cells in the urine.
• Other urine tests may show bacteria in the urine.

An intravenous pyelogram (IVP) or CT scan of the abdomen may show swollen kidneys. These tests can also help rule out underlying disorders.

Additional tests and procedures that may be done include:

• Kidney biopsy
• Kidney scan
• Kidney ultrasound
• Voiding cystourethrogram

With treatment, most kidney infections get better without complications. However, the treatment may need to be aggressive or prolonged.

Pregnant women and persons with diabetes or spinal paralysis should have a urine culture after finishing antibiotic therapy to make sure that the bacteria are no longer present in the urine.

In rare cases, permanent kidney damage can result when:

• Chronic kidney infections occur in a transplanted kidney
• Many kidney infections occur during infancy or childhood

Acute kidney injury (acute renal failure) may occur if a severe infection leads to significantly low blood pressure (shock). The elderly, infants, and persons with a weakened immune system have an increased risk for developing shock and a severe blood infection called sepsis. Often, such patients will be admitted to the hospital for frequent monitoring and IV antibiotics, IV fluids, and other medications as necessary.

Severe episodes of acute kidney injury may result in permanent kidney damage and lead to chronic kidney disease.

• Acute kidney failure
• Kidney infection returns
• Infection around the kidney (perinephric abscess)
• Severe blood infection (sepsis)

Call your health care provider if you have symptoms of pyelonephritis.

Call your health care provider if you have been diagnosed with this condition and new symptoms develop, especially:

• Decreased urine output
• Persistent high fever
• Severe flank pain or back pain

Prompt and complete treatment of bladder infections may prevent development of many cases of pyelonephritis. Chronic or recurrent urinary tract infection should be treated thoroughly.

You can help preventing kidney infections by taking the following steps:

• Keep the genital area clean. Wiping from front to back helps reduce the chance of introducing bacteria from the rectal area to the urethra.
• Urinating immediately after sexual intercourse. This may help eliminate any bacteria that may have been introduced during sexual activity.
• Drink more fluids (64 to 128 ounces per day). This encourages frequent urination and flushes bacteria from the bladder.
• Drink cranberry juice. Doing so prevents certain types of bacteria from attaching to the wall of the bladder and may lessen your chance of infection.

Norrby SR. Approach to the patient with urinary tract infection. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 306

Foster RT Sr. Uncomplicated urinary tract infections in women. Obstet Gynecol Clin North Am. 2008 Jun;35(2):235-48, viii.

Pohl A. Modes of administration of antibiotics for symptomatic severe urinary tract infections. Cochrane Database Syst Rev. 2007 Oct 17;(4):CD003237.