History: 20 year old female with back pain and urinary tract infection.
Xanthogranulomatous Pyelonephritis – Coronal CT of the abdomen and pelvis with intravenous contrast reveals right sided hydronephrosis, cortical thinning, and delayed enhancement. There is extension of the inflammatory process through the perirenal space to the adjacent abdominal wall (yellow arrow). The normal kidney is indicated by the green arrow.
Xanthogranulomatous Pyelonephritis – Axial CT of the abdomen at the level of the kidneys shows a right sided percutaneous nephrostomy tube (yellow arrow) which has been placed to drain the chronically obstructed and infected right kidney. The normal left kidney is indicated by the green arrow.
This is a case of xanthogranulomatous pyelonephritis, which is defined as a chronic infection of the kidney and surrounding structures, destruction of renal parenchyma, and infiltration with lipid-laden macrophages. It is the lipid-laden macrophages which characteristically give this entity its name “xanthogranulomatous.” Xanthos is the Greek word for yellow, which this entity looks like on gross specimens in the pathology lab. Xanthogranulomatous pyelonephritis is usually associated with large staghorn calculi and is difficult to distinguish from other neoplasms such as renal cell carcinoma.
Radiographics article on Xanthogranulomatous Pyelonephritis.
CD68 immunohistochemical staining of macrophages and giant cells in a case of xanthogranulomatous pyelonephritis. In this case, CT findings had suggested the possibility of renal cell carcinoma, thus it was excised. (Photo credit: Wikipedia)