Kidney, Xanthogranulomatous pyelonephritis, Trichrome stain

Xanthogranulomatous pyelonephritis (XGP) is a rare form of chronic pyelonephritis, that is, inflammatory damage and scarring of the kidney tissue. It is often thought to be related to sub-acute/chronic infection, and various bacteria have been isolated. In this case, vesico-ureteral reflux was the initial cause that led to kidney loss, and the same mechanism has led to XGP in the transplant kidney shown in the pictures.

Sections show core and patchy areas of dense interstitial inflammation with tubular injury and tubular loss. The inflammation includes lymphocytes, neutrophils, plasma cells and rare eosinophils, along with foam cells. The tubules show vacuolization and inflammatory cells within the epithelium and the lumina with some RBC casts.

XGP represents a clinical challenge in that it may form a mass lesion that mimics renal cell carcinoma, especially when considering that it is an aggressive process that can involve adjacent structures. As such, surgical management plays a key part of its management.

This slide shows Trichrome stain. See related content for PAS stain.