Bear's Paw Sign: A Classic Presentation of Xanthogranulomatous Pyelonephritis

doi:10.1016/j.urology.2015.04.033

Urology

Volume 86, Issue 2, August 2015, Pages e5-e6

https://doi.org/10.1016/j.urology.2015.04.033 Get rights and content

A 41-year-old woman with recurrent urinary tract infections presented with right flank pain, fever, and anorexia. Physical examination revealed right-sided flank pain and a right-sided unilateral renal mass. Computed tomography of the abdomen and pelvis revealed xanthogranulomatous pyelonephritis with perinephric extension. The bear's paw sign was visualized. The classic radiology triad (unilateral large kidney, renal pelvis stone, and a nonfunctioning or poorly functioning kidney) was also found on computed tomographic imaging. She completed a course of antimicrobial therapy and underwent a nephrectomy. Her post-operative course was uneventful and she was discharged from the hospital on postoperative day 4.

References (2)

C.K. Chuang et al.
Xanthogranulomatous pyelonephritis: experience in 36 cases
J Urol
(1992)
M.A. Parsons et al.
Xanthogranulomatous pyelonephritis: a pathological, clinical and aetiological analysis of 87 cases
Diagn Histopathol
(1983)

Cited by (8)

A pediatric case of xanthogranulomatous pyelonephritis in the setting of Covid-19 and multi-system inflammatory syndrome (MIS-C)
2022, Journal of Pediatric Surgery Case Reports
Citation Excerpt :
In the focal form, a localized intrarenal mass with fluid-like attenuation may be seen [28]. The most commonly described radiologic appearance is the “bear paw” sign, which is due to the presence of multiple, hypoechoic areas of the dilated collecting system with pus and debris that is surrounded by an enhanced rim of contrast medium [28,43,44]. An important distinction to note is the difference between “bear paw” sign seen in XGP and the “claw” sign which has been described in Wilms tumor and refers to a normal rim of renal parenchyma surrounding an inner renal mass [45].
Xanthogranulmatous pyelonephritis is a rare, chronic inflammatory pathology of the kidney. It most commonly arises in middle-aged females, but there are case reports and series described in the pediatric population. Here, we discuss the case of a 14 year old male who presented with xanthogranulomatous pyelonephritis in the setting of Covid-19 and multi-system inflammatory syndrome (MIS-C). As xanthogranulomatous pyelonephritis often mimics other diseases that are more prevalent in the pediatric population, our case was only definitively diagnosed with histopathology after surgical resection. This report is novel in that, to our knowledge, it is the first to describe xanthogranulomatous pyelonephritis in the setting of MIS-C.
Xanthogranulomatous pyelonephritis
2022, American Journal of the Medical Sciences
Epilogue: Anaemia + abdominal mass = is it cancer?
2023, Archives of Disease in Childhood: Education and Practice Edition
Concomitant xanthogranulomatous pyelonephritis with renal abscess - an unusual cause of a right flank mass
2021, International Braz J Urol
Imaging of pyelonephritis
2019, Pain Imaging: A Clinical-Radiological Approach to Pain Diagnosis
Extensive renal sinus lipomatosis in xanthogranulomatous pyelonephritis simulating liposarcoma
2018, International Braz J Urol

View all citing articles on Scopus

View full text

Images in Clinical UrologyBear's Paw Sign: A Classic Presentation of Xanthogranulomatous Pyelonephritis

J Urol

Xanthogranulomatous pyelonephritis: a pathological, clinical and aetiological analysis of 87 cases

Diagn Histopathol

Images in Clinical Urology
Bear's Paw Sign: A Classic Presentation of Xanthogranulomatous Pyelonephritis