Can We Predict the Outcome of Oral Dissolution Therapy for Radiolucent Renal Calculi? A Prospective Study

We prospectively assessed the efficacy and the predictors of the success of oral dissolution therapy by alkalization for lucent renal calculi.Patients with radiolucent renal stones were counseled to undergo oral dissolution therapy, which entails oral potassium citrate 20 mEq 3 times daily, 3 L daily fluid intake and a dietary regimen. The study primary end point was the achievement of a 6-month stone-free rate with oral dissolution therapy. The other end point was a change in stone surface area as measured by noncontrast computerized tomography at 3 and 6 months.Between February 2015 and January 2016 only 182 of the 212 eligible patients who agreed to participate were compliant with oral dissolution therapy and included in the final analysis. Mean stone surface area at enrollment was 1.3 cm (range 0.16 to 11.84). At 3 months 97 (53.2%), 65 (35.7%) and 20 (11.1%) patients were oral dissolution therapy responders (stone-free), partial responders and nonresponders, respectively. Oral dissolution therapy achieved a 6-month stone-free rate of 83%, including 97 and 54 patients after 3 and 6 months of oral dissolution therapy, respectively. On regression analysis the initial 3-month response to oral dissolution therapy (p = 0.001), lower stone density (p = 0.03) and higher urine pH 12 weeks after treatment (p = 0.01) independently predicted the oral dissolution therapy response at 6 months.Regardless of stone size, oral dissolution therapy was an effective treatment approach for lucent renal stones. The initial response to oral dissolution therapy after 3 months was the key factor in determining the potential oral dissolution therapy response after 6 months. In addition, treatment compliance in achieving the targeted urine pH and low stone density has an independent role in the oral dissolution therapy response.