Which factor is most associated with the formation of renal calculi?

Decreased urine volume is significantly associated with the formation of renal calculi, or kidney stones, because it leads to concentrated urine. When urine is concentrated, minerals and waste products can crystallize and form stones. Normally, adequate hydration helps to dilute these substances, minimizing the likelihood of crystal formation.

In contrast, high fluid intake tends to prevent stone formation as it increases urine volume and helps flush out substances that could crystallize. Reduced phosphate levels and a low calcium diet are less directly linked to the common types of kidney stones, such as calcium oxalate stones, which form when there is an imbalance in calcium and oxalate levels in the urine. Thus, the primary factor influencing the risk of kidney stone development is the volume of urine produced, making decreased urine volume a critical factor in renal calculi formation.