This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Which of the followings renal stones may be large and still be asymptomatic for years: March 2011 \nSelect and explain. \nA. Urate, B. Oxalate, C. Staghorn, D. Cystine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Staghorn Phosphate calculus may enlarge to fill most of the collecting system, forming a staghorn calculus. Even a very large straghorn calculus may be clinically silent for years until it signals its presence by hematuria, urinary infection or renal failure Renal calculi: Calcium stones (calcium oxalate and calcium phosphate) makes up 75-85% of the total renal calculi Uric acid stones are radiolucent Uric acid stones are MC in men Struvite stones: - Occur mainly in women or patients who require chronic bladder catheterization - Result from UTI with urease producing bacteria (proteus spp.) - Grow in infected urine Cysteine stones are hard to break in ESWL', 'role': 'assistant'}]