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
[{'content': 'Management of 4 cm size renal stag horn calculus? \nSelect and explain. \nA. ESWL, B. PCNL, C. Intra renal repair surgery, D. Open pyelolithotomy', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) PCNLRef Smith Urology 17th edition, Page page 114; Surgery Sixer 2nd Edition, Page 735 repeat question* Latest treatment of such 4cm size Stag horn stone is "Sandwich technique"--using both ESWL and PCNL. They will break the stone into multiple pieces before and remove by PCNL.', 'role': 'assistant'}]