Calcium Phosphate Nephrolithiasis: A Comprehensive Review

In this article, we review the recent epidemiology, unique pathophysiology, and challenges in medical management of calcium phosphate (CaP) kidney stones. CaP stones represent the second most encountered stone type. Compared with the more common calcium oxalate stones, CaP stones are more likely to occur in women, have increased in prevalence in recent decades, and recur at a higher rate. Stone formers presenting with hydroxyapatite and brushite stones, the 2 most common subtypes of CaP stones, exhibit distinct histopathologic findings. Urinary risk factors contributing to CaP stone formation include high urine pH, hypercalciuria, and hypocitraturia. These changes in the urinary environment occur from a variety of inherited or acquired conditions. The current approach to medical management of CaP stones is primarily extrapolated from studies performed in calcium oxalate stone formers, and the role of alkali therapy in CaP stone formers is controversial. Therefore, there is a critical need for treatments tailored to address the high recurrence rate, distinct pathophysiology, and risk factors of CaP nephrolithiasis.