Triple phosphate (struvite) crystals are favored by alkaline urine. If they are not seen on a day they are typically present, what is the most likely explanation?

Triple phosphate (struvite) crystals are favored by alkaline urine. If they are not seen on a day they are typically present, what is the most likely explanation?

• A. Phase contrast is required to view these crystals
• B. The urine pH must be acidic
• C. Polarized microscopy is needed to view these crystals
• D. The concentration of the salt is too high for crystals to form

Answer: (B)

Struvite crystals form best in alkaline urine because the high pH promotes the precipitation of magnesium ammonium phosphate. When urine is acidic, these salts stay dissolved, so the crystals may not form or be seen on a day when the urine isn’t alkaline. The absence isn’t about needing special microscopy; standard light microscopy is sufficient to view these crystals when present, so phase contrast or polarized light isn’t the limiting factor. Also, having a very high solute concentration would tend to promote crystallization rather than prevent it, so that option doesn’t explain the absence.

Struvite crystals form best in alkaline urine because the high pH promotes the precipitation of magnesium ammonium phosphate. When urine is acidic, these salts stay dissolved, so the crystals may not form or be seen on a day when the urine isn’t alkaline. The absence isn’t about needing special microscopy; standard light microscopy is sufficient to view these crystals when present, so phase contrast or polarized light isn’t the limiting factor. Also, having a very high solute concentration would tend to promote crystallization rather than prevent it, so that option doesn’t explain the absence.