Oral dissolution therapy for renal radiolucent stones, outcome, and factors affecting response: A prospective study

Urolithiasis is a widespread problem, that affects up to 10% of population. Uric acid stones come second to calcium stones in prevalence (around 10% of urolithiasis). Potassium citrate is currently the treatment of choice for urine alkalization with minimal side effects and high tolerability.

This study is trying to present the outcome of oral dissolution therapy (ODT) for treating radiolucent renal stones and evaluating factors affecting its success in a prospective manner.

Between 2015 and 2018, 147 patients with solitary radiolucent renal stones were offered ODT using potassium sodium hydrogen citrate (K citrate). The study included patients diagnosed by noncontrast computed tomography (NCCT) with stone size of 5-30 mm in the longest dimension and attenuation less than 600 Hounsfield units (HU). Patient compliance, blood pressure, creatinine level, K level, and tolerance to side effects were followed up at days 3, 7, and 15 and then monthly for 3 months. Follow-up renal ultrasound at 6-week intervals and a final NCCT at the end of treatment. Successful dissolution was defined as complete stone dissolution or residual that measures up to 2 mm in maximum length. Data were collected, tabulated, and analyzed using Stata 12.0 software (Stata Corporation, College Station, TX, USA).

One hundred and thirty-nine patients were included in the analyses. The age was 45.1 ± 10.5 years. DJ stent was used in 47 (33.8%) patients. Overall response rate was 64.8%. The stone location within the kidney (pelvic or calyceal) showed no difference between responders and non-responders. Stone longest diameter was smaller in responders (17 ± 5.7 mm) versus 19.2 ± 6.1 mm in nonresponders (P value = 0.039). The mean stone attenuation value (HU) was also lower in responders (347.4 ± 68.5 HU) versus (428.9 ± 84.0 HU) in nonresponders with P < 0.001. DJ insertions seemed to have marginal effect on stone dissolution on univariate analysis but found insignificant in multivariate analysis.

ODT is safe and effective in the treatment of radiolucent renal stones. The efficacy was affected by stone density and stone size with more tendencies to failure with bigger stones and denser stones. Double J stent insertion may facilitate dissolution rate. There was no effect of the baseline urinarypH, hyperuricemia, or stone location on the dissolution rate of the stones.