Serial crystalluria determination and the risk of recurrence in calcium stone formers

Serial crystalluria determination and the risk of recurrence in calcium stone formers. 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. All stone events which occurred prior to referral, then after entry in the study were recorded. Results As compared with 109 patients who had no evidence of stone recurrence during follow-up, the 72 patients who experienced ≥ one recurrent stone event had a lower daily urine volume (1.74 ± 0.06 vs. 2.26 ± 0.05 L/day (mean ± SEM) ( P P Conclusion These data provide evidence that crystalluria, when repeatedly found in early morning urine samples, is highly predictive of the risk of stone recurrence in calcium stone formers. Serial search for crystalluria, a simple and cheap method, may be proposed as a useful tool for the monitoring of calcium stone formers, in addition to urine biochemistry.