Contemporary urological intervention for cystinuric patients: immediate and long-term impact and implications

Abstract

Purpose: We determined the immediate efficacy of contemporary urological intervention for cystine stones and the impact of such intervention on the subsequent rate of recurrent stone formation.

Materials and methods: A total of 31 cystinuric patients underwent selected intervention for 61 stone events. Patients were subsequently followed at 6 to 12-month intervals while being treated with standard medical therapy. Logistic regression models were used to correlate potential risk factors with the efficacy of the intervention in achieving a stone-free status. Kaplan-Meier estimates of the probability of recurrence-free survivals at 1 and 5 years were generated, and risk factors for stone recurrence were analyzed using the log rank test.

Results: Overall stone-free rate was 86.9%, which was not significantly influenced by the initial stone burden or type of intervention selected. The probability of recurrence-free survival at 1 and 5 years was 0.73 and 0.27, respectively, and again this probability was independent of initial stone burden or type of intervention selected. Urinary cystine levels before intervention and post-procedure residual stone status also failed to impact significantly on the risk of recurrence. However, a stone-free result, in contrast to residual stones, prolonged the mean time to stone recurrence from 346 to 1,208 days.

Conclusions: While cystine stones are not amenable to all currently available minimally invasive therapeutic modalities, high stone-free rates can be achieved without the need for open surgery and as such cystinuric patients clearly benefit from contemporary intervention. When such intervention is used selectively, with consideration given primarily to stone burden and location, rates of recurrence will relate primarily to the natural history of the medically treated cystinuric patient, and not the type of intervention applied.