This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urolithiasis, Subject name: Surgery
[{'content': 'Recurrent infection leads to which calculi - \nSelect and explain. \nA. Struvite, B. Calcium Oxalate, C. Calcium Phosphate, D. Cysteine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Struvite "Struvite stone tends to grow in alkaline urine * esp. when proteus organisms are present which split urea to ammonia ".Struvite Stoneso Calcium phosphate can be combined with ammonium and magnesium to form the triple phosphate calculus* ie Calcium amnomium magnesium phosphate also k/a struvite stones.# Smooth and dirty white and soltitary*.# Seen in alkaline urine esp with proteus infection which split urea to ammonia.o This type of calculus may enlarge to fill all or most of the renal collecting system forming a staghorn calculus*.', 'role': 'assistant'}]