This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney & Ureturs, Subject name: Surgery
Management of 4 cm size renal staghorn calculus. 
Select and explain. 
A. Extracorporeal shock wave lithotripsy (ESWL), B. Percutaneous nephrolithotomy (PCNL), C. Pyeloplasty, D. Open pyelolithotomy
B: Percutaneous nephrolithotomy (PCNL)
Answer: B: Percutaneous nephrolithotomy (PCNL) 
Explanation: ANS. B* Management of renal calculi* Stones <6 mm--conservative treatment* Stones from 6 mm to 2 cm: ESWL* Stones >2 cm: PCNL* For stones at lower renal calyx: Do PCNL* For staghorn calculi: ESWL+PCNL (Sandwich technique)Shapes of urinary stonesLeucine stones--spherical-shapedTyrosine stones--needle-shaped