Xanthogranulomatous pyelonephritis

Case contributed by Assoc Prof Frank Gaillard


Upper abdominal discomfort, vague constitutional symptoms and reduced renal function.

Patient Data

Age: Elderly
Gender: Female

Abdominal x-ray

X-ray demonstrates a large right sided branched calculus which appears fragmented. 

CT demonstrates enlargement of the right kidney with multiple large renal calculi and rounded low density regions associated with the calculus. The left kidney is markedly atrophic.

Annotated image

Single image from the CT with the right kidney outlined. Note how the dilated low density calyces form an appearance which has been likened to that of the pads of a bear paw. 


MRI abdomen

MRI demonstrates an enlarged right kidney with heterogeneous signal, hydronephrosis and a staghorn calculus. 

Case Discussion

Features are consistent with xanthogranulomatous pyelonephritis and pre-existing staghorn calculus.

Case courtesy of Dr Laura Jimenez Juan (CT) and Dr Natalie Yang (MRI)

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Case information

rID: 9931
Published: 1st Jun 2010
Last edited: 1st Aug 2021
Inclusion in quiz mode: Included