Calcium oxalate stones are most associated with which risk factors?

• A. Hyperoxaluria, low urine volume, and hypercalciuria.
• B. Hypercalciuria, hyperuricemia, and cystinuria.
• C. Hyperoxaluria, high urine volume, and low calcium.
• D. Low oxalate intake, high urine volume.

Answer: (A)

Calcium oxalate stones form when urine is highly saturated with both calcium and oxalate, so anything that raises either component or concentrates the urine increases the risk. The strongest contributors are hyperoxaluria (too much oxalate in the urine), hypercalciuria (too much calcium in the urine), and low urine volume (which concentrates all solutes and promotes crystallization). Other conditions listed, like high urine volume, actually reduce stone risk by diluting the urine, and issues such as hyperuricemia or cystinuria point to uric acid or cystine stones rather than calcium oxalate stones. Dietary calcium can influence oxalate absorption, but the key risk factors for calcium oxalate stones are high oxalate in urine, high calcium in urine, and a low urine volume, which together drive the precipitation of calcium oxalate crystals.