In urolithiasis, struvite crystals are primarily composed of which compound?

In urolithiasis, struvite crystals are primarily composed of which compound?

• A. Calcium carbonate
• B. Calcium oxalate
• C. Silica
• D. Magnesium phosphate

Answer: (D)

Struvite stones form when urine becomes alkaline due to urease-producing bacteria breaking down urea into ammonia. This high pH causes precipitation of magnesium ammonium phosphate, the compound that makes up struvite (magnesium ammonium phosphate hexahydrate). So, magnesium phosphate is the best match because it reflects the key components of struvite. Other minerals listed form different stone types under different conditions—calcium-containing stones and silica stones arise from other pathways, not the infection-related, alkaline-urine mechanism that produces struvite.

Struvite stones form when urine becomes alkaline due to urease-producing bacteria breaking down urea into ammonia. This high pH causes precipitation of magnesium ammonium phosphate, the compound that makes up struvite (magnesium ammonium phosphate hexahydrate). So, magnesium phosphate is the best match because it reflects the key components of struvite. Other minerals listed form different stone types under different conditions—calcium-containing stones and silica stones arise from other pathways, not the infection-related, alkaline-urine mechanism that produces struvite.