Xanthogranulomatous Pyelonephritis

The patient is a 65-year-old white female who presented with a five day history of coug (which had been productive of yellow sputum) and malaise. CT scan of C/A/P revealed a large left lower lobe abscess as well as a poorly enhancing left kidney with numerous staghorn type calculi. There was abscess extension from the superior pole of the left kidney to include the left lower lobe of the lung (not shown). White count and fever abated after decortication, extended antibiotic administration, and left nephrectomy. Pathology revealed lipid laden macrophages of the kidney typical of xanthogranulomatous pyelonephritis.
Xanthogranulomatous pyelonephritis (XGP) is a rare and unusual variant of chronic pyelonephritis in which is a complication of an obstructed and infected renal unit. It is most common in middle aged women with history of recurrent urinary tract infections. UA usually reveals pyuria and bacteriuria. Most commonly associated organisms are E. coli, Proteus, mirabilis, Klebsiella, and Providencia. 10% of patients have diabetes. XGP is usally unilateral and often results in destruction of the kidney requiring nephrectomy. CT scan is the preferred diagnostic tool in the evaluation of XGP. Typical findings include a large staghorn calculus (~75%) on the background of a large and nonexcreting (nonfunctioning) kidney.
References:
1. Dähnert W. Radiology Review Manual 5th edition. Lippincott, Williams & Wilkins, 2003.
2. Weissleder et al. Primer of Diagnostic Imaging 3rd edition. Mosby, 2003.
3. UpToDate.com
Credit: Dr John Asleson
http://www.radpod.org