Urology And Nephrology Practice Test

Struvite stones form in the setting of infection with which organisms and alkaline urine?

Urease-producing bacteria (e.g., Proteus); alkaline urine. Staphylococcus aureus; neutral urine. Pseudomonas; acidic urine.

Correct Answer:

Urease-producing bacteria (e.g., Proteus); alkaline urine.

Explanation:

Struvite stones form when urine becomes alkaline due to urease-producing bacteria. Urease splits urea into ammonia, which raises the urine pH. In this alkaline environment, magnesium, ammonium, and phosphate precipitate as magnesium ammonium phosphate, the composition of struvite. Organisms like Proteus species commonly drive this process, leading to infection-related stones that can grow large and form branching “staghorn” calculi. Other bacteria that don’t produce urease don’t create the same alkaline conditions, so they’re not typically associated with struvite stone formation.

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