The biochemical stone screen is justified

Introduction: Although the value of biochemical screening is not accepted by all urologists, the treatment of abnormalities can significantly reduce subsequent stone events. A simplified stone screen was developed for patients presenting with stone disease. Patients and methods: From March 1995 to December 1996. all patients presenting with new or recurrent stones were investigated. Serum was sent for analysis of calcium, urate and creatinine, and two 24-h urine samples were measured for volume, pH, calcium, oxalate, urate, citrate and cystine. Each stone screen cost £35. Results: Of 117 patients for whom data were complete, the overall abnormality rate was 73% (see table); 10 patients (8.5%) had impaired renal function with high creatinine and 75 patients (64%) had urine and blood abnormalities predisposing to stone formation. Urine, n (%) Blood. n (%) Hypercalciuria 33 (28) Hypercalcaemia 1 (1) Hyperoxaluria 20 (17) Hyperuricaemta 5 (4) Hyperuricosuria 8 (7) High creatinine 10 (9) Volume <1500 mL 26 (22) Cystine 0 The citrate assay was only available for 83 patients, a low value was found in four (5%). The one patient with hypercalcaemia was subsequently proved to have primary hyperparathyroidism. Conclusions: This study detected a surprisingly high incidence of potentially treatable biochemical abnormalities. This may reflect recruitment from both urological and nephrological departments. As appropriate dietary and drug treatment reduces the incidence of stone events, we conclude that screening is both justified and likely to be cost-effective.