Calcium phosphate stones are not uncommon, making up about 15-20% of all calcium stones. The cause of calcium phosphate stones is often obscure but usually is related to a high urine pH. Treatment of calcium phosphate stones is controversial because the use of citrate is not backed by any trials. This controversy about the use of alkali is long-standing.
My dream RCT is not difficult then to imagine. Patients with recurrent calcium phosphate stones would be included. The participants would then be randomly assigned to one of 2 regimens: usual care plus placebo or usual care plus 20 mEq of potassium citrate twice a day. 24h urine collections, CT scans and stone episode questionnaire would be performed yearly. All stone episodes including emergency room visits and urological interventions and spontaneous stone passage would be recorded. The primary outcome would be the recurrence of new stones, both asymptomatic and symptomatic.