Presentation
Left flank pain with hematuria.
Patient Data
Enlarged left kidney with a distorted renal outline. Contracted renal pelvis and proximal ureter with a thick enhanced wall (ureteropyelitis). Fragmented staghorn calculus with dilated multiloculated calyces giving the appearance of a paw print of a bear "bear's paw sign". No perinephric inflammatory change or thickening of Gerota's fascia.
Multiple left para-aortic lymphadenopathies (short axis up to 16 mm).
Normal appearance of the right kidney except for tiny cortical cysts.
Normal Urinary bladder.
Case Discussion
The CT features are most consistent with xanthogranulomatous pyelonephritis, typically occurring in presence of a staghorn calculus.