Horseshoe kidney with simultaneous occurrence of calculi, transitional cell and squamous cell carcinoma.

The simultaneous occurrence of invasive renal pelvic carcinoma with hydronephrosis and multiple calculi was noted after resection of the involved left renal unit of a horseshoe kidney. A perirenal lymph node submitted with the specimen was also involved necessitating a "second look" with retroperitoneal lymph node dissection and removal of left lower ureter and cuff of the bladder, all of which were benign. The increased incidence of renal pelvic tumors with horseshoe kidney is discussed. While the occurrence of adenocarcinoma in a horseshoe kidney appears to be no higher than in nonfused kidneys, the incidence of transitional cell carcinoma among horseshoe tumors is higher (24% vs. 7.7% in nonfused kidneys).