Which crystal is commonly associated with alkaline urine and urinary tract infections (infection stones)?

Which crystal is commonly associated with alkaline urine and urinary tract infections (infection stones)?

• A. Uric acid crystals
• B. Struvite crystals
• C. Calcium oxalate crystals
• D. Cystine crystals

Answer: (B)

Struvite crystals form in alkaline urine and are linked to urinary tract infections caused by urease-producing bacteria. These bacteria release urease, which splits urea into ammonia and carbon dioxide. The ammonia raises the urine pH, creating conditions that favor precipitation of magnesium ammonium phosphate, the composition of struvite. In microscopy, they often look like coffin-lid shapes and can develop into large stones known as infection stones or staghorn calculi, commonly seen with chronic UTIs. This direct association with both alkaline urine and infection makes them the best answer. Uric acid crystals form in acidic urine and appear as rhomboid or rosette shapes, not tied to infection. Calcium oxalate crystals are common stone formers with envelope or dumbbell shapes and a broader range of pH. Cystine crystals are hexagonal and indicate cystinuria, a genetic condition, not an infection-related stone.

Struvite crystals form in alkaline urine and are linked to urinary tract infections caused by urease-producing bacteria. These bacteria release urease, which splits urea into ammonia and carbon dioxide. The ammonia raises the urine pH, creating conditions that favor precipitation of magnesium ammonium phosphate, the composition of struvite. In microscopy, they often look like coffin-lid shapes and can develop into large stones known as infection stones or staghorn calculi, commonly seen with chronic UTIs. This direct association with both alkaline urine and infection makes them the best answer.

Uric acid crystals form in acidic urine and appear as rhomboid or rosette shapes, not tied to infection. Calcium oxalate crystals are common stone formers with envelope or dumbbell shapes and a broader range of pH. Cystine crystals are hexagonal and indicate cystinuria, a genetic condition, not an infection-related stone.