Xanthogranulomatous Pyelonephritis of a Lower Pole Moiety in a Duplicated Collecting System Kidney

Figure 1

Abdominal CT scan on initial evaluation revealed a large enhancing retroperitoneal fluid collection measuring  cm (yellow arrow) extending into entire left psoas muscle and hip region. There were bilateral complete duplicated collecting systems with bilateral obstructing large UPJ calculi in both lower pole moieties. The left kidney was remarkable for moderate hydronephrosis of the upper pole moiety and severe cortical thinning of the lower pole. The left kidney was duplicated with moderate upper pole hydronephrosis and moderate-to-severe hydronephrosis with cortical thinning of the lower pole moiety (green arrow). The right kidney had preserved parenchyma with associated emphysematous pyelitis (blue arrow).