Undissociated Uric Acid in Nephrolithiasis

It is generally accepted that hyperuricosuria is not the main cause of urinary uric-acid supersaturation in uric acid nephrolithiasis (NU), where urinary supersaturation is mainly related to a low urinary pH (1–4), However, quantitative evaluations of undissociated uric acid (FUa) are not readily available in patients with NU or other kinds of nephrolithiasis.