bear’s-paw sign

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bear’s-paw sign

A radiologic sign referring to the cross-sectional appearance of the kidney which has been fancifully likened to bear’s paw: the renal pelvis is contracted while the calyces are dilated, thus mimicking the paw’s toe-pads. It is regarded as a classic finding in xanthogranulomatous pyelonephritis, but has also been described in ongenital ureteropelvic junction obstruction.