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Kidney infection (pyelonephritis)

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Definition:

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

Alternative Names:

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

Causes, incidence, and risk factors:

Pyelonephritis most often occurs as a result of urinary tract infection , particularly in the presence of occasional or persistent backflow of urine from the bladder into the ureters or kidney pelvis ( vesicoureteric reflux ).

Pyelonephritis can be further classified as follows:

• Acute uncomplicated pyelonephritis (sudden development of kidney inflammation)
• Chronic pyelonephritis (a long-standing infection that does not clear)

Although cystitis (bladder infection) is common, pyelonephritis occurs much less often. The risk is increased if there is a history of cystitis, renal papillary necrosis , kidney stones , vesicoureteric reflux, or obstructive uropathy .

The risk is also increased when there is a history of chronic or recurrent urinary tract infection and when 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 ).

• Review Date: 7/25/2006
• Reviewed By: David M. Charytan, M.D., M.Sc., Department of Medicine, Division of Nephrology, Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.

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