Urinary tract infection - complicated; Infection - kidney; Complicated urinary tract infection; Kidney infection
Pyelonephritis is an infection of the kidney and the ureters, the ducts that carry urine away from the kidney.
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).
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:
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).
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.