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
Renal calculi associated with proteus infection? 
Select and explain. 
A. A.Uric acid, B. B.Triple phosphate, C. C.Calcium oxalate, D. D.Xanthine
B: B.Triple phosphate
Answer: B: B.Triple phosphate 
Explanation: Urease producing organisms eg :- proteus ,psuedomonas , and staphylococcus , break down urea to produce ammonia and CO2.The urine becomes alkaline which promotes formation of struvite calculi ( magnesium ammonium phosphate ) which grow to become staghorn calculi.E coli never forms struvite stones. Struvite occupying pelvi-calyceal system:- TYPES:1.Complete- occupancy of > 80%of pelvi- calyceal system. 2.Incomplete:- Occupancy of atleast 2 pelvicalyceal system. ref :- Bailey and Love 27th edition .chapter 72 . pg no 1406