Bone formation in the urinary tract is a rare phenomenon. Osseous metaplasia in the kidney which presented as a pelvolithiasis is presented in this case. The patient consulted with a complaint of left subcostal mass. Ultrasound revealed nephrolithiasis with hydronephrosis of the left kidney while CT stonogram revealed staghorn calculus with hydronephrosis. Subsequently, left nephrectomy was performed. Grossly, the kidney was enlarged to 11.5m x 5cm x 3cm on cut section with an intrarenal mass measuring 7cm x 6.5cm x 6cm composed of tan gray irregular hard tissue. Histopathologically, the renal mass consisted of benign compact and cancellous bone wherein osseous metaplasia was considered.
Osseous Metaplasia ; Heterotopic Bone Formation ; Bone Lithiasis ; Nephrolithiasis