American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the potential complication of urine alkalinization in the setting of hyperphosphatemia?

1. Precipitation of calcium phosphate crystals

2. Increased uric acid levels

3. Dehydration

4. Electrolyte imbalances

The correct answer is: Precipitation of calcium phosphate crystals

Urine alkalinization can lead to the precipitation of calcium phosphate crystals, particularly in the context of hyperphosphatemia. When urine pH is elevated, the solubility of calcium phosphate decreases, making it more likely for these crystals to form and precipitate. This is particularly relevant when there is already an excess of phosphate in the bloodstream, as is the case in hyperphosphatemia. The presence of high phosphate levels in the body can drive calcium and phosphate to combine and create insoluble complexes, which can lead to conditions such as nephrolithiasis (kidney stones) or calcifications in renal tissue. Thus, among the potential complications of urine alkalinization, the risk of calcium phosphate crystal precipitation is significant and needs to be carefully monitored in patients with underlying renal issues or disturbances in phosphate metabolism. Other options, while they may present challenges in different clinical scenarios, do not directly relate to the specific complication arising from urine alkalinization in the setting of hyperphosphatemia.