Renal calculi associated with Proteus infection:

Ans is 'b' i.e. Triple phosphate Repeat from All India 09, AIIMS Nov 97Phosphate or struvite stones are infection stones associated with urea splitting organisms i.e. Proteus, Pseudomonas, Providencia, Klebsiella, Staphylococci and Mycoplasma.The high ammonium concentration derived from the urea-splitting organisms results in an alkaline urinary pH, required for the precipitation of phosphate crystals.Types of Renal CalculusCalcium oxalate calculus {Most common*)they have hard, small and jagged surfacePhosphate calculuscalcium phosphate but can be combined with ammonium and magnesium to form the triple phosphate calculus * ie Calcium ammonium magnesium phosphate also k/a struvite stones.smooth and dirty white and solitary*.seen in alkaline urine esp with proteus infection which split urea to ammonia.this type of calculus may enlarge to fill all or most of the renal collecting system forming a staghorn calculus*.Uric acid and urate calculusthese are radiolucent*form in acidic urinemost responsive to lithotripsyCysteine stonesuncommon, seen in cystinuriaappear only in acidic urine *they are pink to yellow when first removed but they change colour to a greenish hue when exposed to air.extremely hard stonesare relatively resistant to fragmentation by ESWLXanthine calculiare radiolucent*are secondary to a congenital deficiency of xanthine oxidaseIndinavir calculiIndinavir is a protease inhibitor used in AIDS patients. It results in calculi in ~6% pt. who used indinavir.Indinavir calculi are radiolucent.Rare CalculiSilicate stonesassociated with the long term use of antacids containing silicaTriamterene stonesassociated with antihypertensive medications containing triamtereneare radiolucent