Abstract: The search identified one study of 125 children (72 boys and 53 girls) with calcium-containing idiopathic nephrolithiasis and normal renal morphology following initial treatment with shockwave lithotripsy (SWL). Patients were randomized to oral potassium citrate 1 mEq/kg per day for 12 months versus no specific medication or preventive measure with results reported for a total of 96 patients (48 per group). This included children who were stone-free (n = 52) or had residual stone fragments (n = 44) following SWL. Primary outcomes: Medical therapy may lower rates of stone recurrence with a risk ratio (RR) of 0.19 (95% confidence interval (CI) 0.06 to 0.60; low quality evidence). This corresponds to 270 fewer stone recurrences per 1000 (133 fewer to 313 fewer) children. We downgraded the quality of evidence by two levels for very serious study limitations related to unclear allocation concealment (selection bias) and a high risk of performance, detection and attrition bias. While the data for adverse events were incomplete, they reported that six of 48 (12.5%) children receiving potassium citrate left the trial because of adverse effects. This corresponds to a RR of 13.0 (95% CI 0.75 to 224.53; very low quality evidence); an absolute effect size estimate could not be generated. We downgraded the quality of evidence for study limitations and imprecision. We found no information on retreatment rates. Secondary outcomes: We found no evidence on serum electrolytes, 24-hour urine collection parameters or time to new stone formation. We were unable to perform any preplanned secondary analyses. Oral potassium citrate supplementation may reduce recurrent calcium urinary stone formation in children following SWL; however, our confidence in this finding is limited. A substantial number of children stopped the medication due to adverse events. There is no trial evidence on retreatment rates. There is a critical need for additional well-designed trials in children with nephrolithiasis.

Plain-language summary: We examined research published up to 14 February 2017. We looked for studies of boys and girls from age one to 18 years who sometime before had problems with kidney stones and who were assigned to a different diet or a medicine (or both) to stop the stones from coming back for at least 12 months. We were most interested in whether the stones returned, how many side effects there were and if children had to have more treatments for kidney stones. We only found one small study with 125 children (72 boys and 53 girls) who had been treated with waves similar to those that carry sound, so-called shock waves to treat their kidney stones. These children formed kidney stones for unknown reasons and had otherwise normal kidneys. Fifty-two children had no more stones and 44 children still had small stone pieces left when they started the study. One group was given a medicine by mouth called potassium citrate; the other group was given no special medicine. The children were on this study for about two years. The study reported on the findings in 96 children; 48 in each group. Based on this study, we found that this medicine may result in stones coming back less often. However, we are not sure about this finding because the study was not of good quality and small. One in eight patients stopped the medicine because of side effects. We did not find any information on how often children had to be treated for stones again. The evidence quality for stones coming back less often was low and that for side effects very low. We found no evidence on how often children had to be treated for stones again.