This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
Stag horn calculi associated with Proteus infection are? 
Select and explain. 
A. Uric acid stones, B. Triple phosphate stones, C. Calcium oxalate stones, D. Cysteine stones
B: Triple phosphate stones
Answer: B: Triple phosphate stones 
Explanation: Triple phosphate or struvite ( Calcium phosphate with ammonium magnesium phosphate ) is smooth and diy white. It grows in alkaline urine, especially when urea splitting organisms like proteus are present and break urea to ammonia and co2 and make urine alkaline. they enlarge to fill most of the collecting system forming a staghorn calculus. Reference : Bailey and Love's sho practice of surgery 27th edition , chapter 76 , pg no 1406