Most commonly caused by chronic vesicoureteral reflux.
Diagnosis is clinical and confirmed with imaging studies. Typically, a biopsy is not performed.
There is no specific treatment, as damage is irreversible.
May result in end-stage renal disease.
Pyelonephritis - from the Greek "pyelo" (pelvis), "nephros" (kidney), and "itis" (inflammation) - refers to an inflammation of the kidney that can be acute, recurrent, or chronic. Chronic pyelonephritis is a complex renal disorder characterized by chronic tubulointerstitial inflammation and deep segmental cortical renal scarring and clubbing of the pelvic calyces as the papillae retract into the scars. It is an important cause of end-stage renal disease (ESRD). The term chronic pyelonephritis is sometimes used synonymously with interstitial nephritis, reflux nephropathy, and chronic atrophic pyelonephritis, and encompasses relatively rare but severe variants such as xanthogranulomatous pyelonephritis (XGP) and emphysematous pyelonephritis (EPN). 
Professor of Medicine
Division of Nephrology
University of California
LF declares that she has no competing interests.
Dr Frassetto would like to gratefully acknowledge the assistance of Donna M. Frassetto. DMF declares that she has no competing interests.
Cleveland Clinic Foundation
PS declares that she has no competing interests.
Consultant Nephrologist and Clinical Director
St Helier Hospital
JM declares that he has no competing interests.
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