Imaging Findings of Xanthogranulomatous Pyelonephritis: what to look for?
Type:Educational Electronic Presentation
Authors: Felipe Montevechi Luz, Kairo Alexandre Alves Silveira, Daniel Lahan Martins, Nelson Marcio Gomes Caserta
Keywords:Xanthogranulomatous Pyelonephritis; Kidney; Chronic Infection.
Educational objective

1- To review some risk factors and clinical presentation of xanthogranulomatous pyelonephritis (XGP).

2- To understand the correlation between the radiology study and the pathology specimen.

3- To illustrate imaging findings of xanthogranulomatous pyelonephritis.

Topic Review

Xanthogranulomatous pyelonephritis is a rare and aggressive chronic granulomatous process, induced by recurrent bacterial urinary tract infection inciting a chronic but incomplete immune reaction.


XGP is most frequently seen in women, diabetics and middle-aged patients. Clinical presentation is often nonspecific and pyuria and positive urinary cultures are present in the majority of cases. The most commonly isolated organisms are Escherichia coli and Proteus mirabilis.


The gross pathological features of the disease are characterized by unilateral renal enlargement and the predominance of lipid (foamy) macrophages in the renal parenchyma, which is replaced by a yellowish, irregular mass around the pelvis and renal calyces. In most cases, staghorn calculus is present with some degree of associated hydronephrosis. (Figure... more

Figure 1. Photograph of anatomical structures (A, B) showing dilated renal calyces (arrowheads). Around it, there is a predominance of lipid macrophages (foamy) in the renal parenchyma, represented by a yellowish and irregular mass (arrows). Note the fragments of the staghorn calculus (circles).
Figure 2. CT, axial plane, excretory phase. An enlarged non-functional kidney with reduced parenchymal thickness, dilation of the renal calyces, a contracted renal pelvis, and a staghorn stone (arrow).


This exhibit is designed to highlight the main clinical, pathological, and radiological findings of chronic xanthogranulomatous pyelonephritis. CT should be performed to characterize renal involvement and assess the extent of the inflammatory process prior to surgery. The radiologist needs to know these clues for the diagnosis of this disease, which is often confused with a true neoplasm.

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