Background: Urinary crystal precipitation is the necessary initial step in kidney stone formation. However, clinical relevance of crystalluria in the evaluation of stone formers is disputed.
Methods: We serially determined crystalluria in first-voided morning urine samples, together with full 24-hour urine biochemistry, in 181 patients with idiopathic calcium nephrolithiasis who had formed at least one calcium-oxalate stone and were followed for at least 3 years under our care.