American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the normal urine pH range targeted for preventing uric acid nephrolithiasis?

1. 4.5 to 5.5

2. 6.1 to 7.0

3. 7.1 to 8.0

4. 5.6 to 6.0

The correct answer is: 6.1 to 7.0

The normal urine pH range targeted for preventing uric acid nephrolithiasis is indeed between 6.1 and 7.0. The solubility of uric acid is significantly influenced by urine pH; at a lower pH (more acidic), uric acid is less soluble and more likely to precipitate, forming stones. By maintaining a urine pH within this range, uric acid can remain soluble and be eliminated through urine rather than crystallizing into stones. Maintaining a urine pH in this targeted range is often achieved through dietary modifications, such as increasing fluid intake and consuming foods that can alkalinize the urine. This is important for patients who have a history of uric acid stones or are at risk for developing them, as it minimizes the likelihood of stone formation. In contrast, the other options denote urine pH levels that would lead to a more acidic environment, where uric acid crystallization is favored, thus increasing the risk of uric acid nephrolithiasis.