A 74-year-old woman presented with spiking fever and right back pain.
Ultrasonography (US) revealed that her right kidney was enlarged. Comp
uted tomography (CT) showed the parenchyma was replaced by non-enhanci
ng masses but the overall kidney shape was maintained. These findings
were compatible with those of xanthogranulomatous pyelonephritis (XP).
The nonenhancing masses on CT coincided with the multiple butter yell
ow nodules of the resected kidney and microscopically these lesions we
re proved to be abscesses with xanthoma cells. In this case, the US an
d CT findings reflected the pathological feature of XP and thus these
techniques are thought to be useful for the diagnosis of XP.