Kidney Week

Abstract: PUB023

Bear Paw: An Ominous Sign

Session Information

• Publication Only

Category: Acute Kidney Injury

• 102 AKI: Clinical, Outcomes, and Trials

Authors

• Aamir, Nawal, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States

Nawal Aamir, MD

• Aulakh, Gagan, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States

Gagan Aulakh, MD

• Ralto, Kenneth M., University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States

Kenneth M. Ralto, MD, FASN

• Pandit, Amar, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States

Amar Pandit, MD

• Montague, Jahan, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States

Jahan Montague, MD

Introduction

Xanthogranulomatous pyelonephritis (XGP) is a rare destructive renal infection characterized by chronic obstruction, infection, and parenchymal replacement by lipid laden macrophages, often requiring nephrectomy for cure. For nephrologists, XGP may present as non resolving “obstructive” AKI despite apparent decompression, forcing nuanced decisions about drainage versus nephrectomy in patients with limited renal

Case Description

An 83 year old woman with CKD 4/A2 (baseline creatinine 1.7–1.9 mg/dL) hypertension, nephrolithiasis, and atrial fibrillation presented with right flank pain, hyponatremia, and AKI in the setting of right proximal ureteral calculus and hydronephrosis. She underwent urgent cystoscopy, ureteroscopy, and right double J stent placement for presumed post renal AKI, ATN 2/2 contrast associated and hemodynamic injury. Creatinine rose to 3.18 mg/dL with persistent unilateral hydronephrosis and leukocytosis. MAG3 renography showed minimal right kidney function, and CT demonstrated an enlarged kidney with calyceal destruction, stones, gas, and classic “bear paw” morphology, consistent with XGP.

Discussion

This case underscores key nephrology lessons: (1) persistent hydronephrosis and leukocytosis after stenting should prompt early functional imaging to distinguish true obstruction from a chronically nonfunctional, XGP destroyed kidney; (2) in advanced XGP, percutaneous nephrostomy may offer little benefit and substantial procedural risk; and (3) nephrectomy in XGP is primarily an infection control strategy rather than a renal salvage intervention, demanding careful timing and multidisciplinary planning in patients with advanced CKD.