Long-term effects of potassium citrate therapy on hypocitraturic calcium stones: a prospective randomized study

Background: Potassium citrate effectively reduces recurrence of hypocitraturic calcium nephrolithiasis. Objective: To evaluate the impact of long-term potassium citrate therapy on urinary metabolic parameters and stone recurrence rates in patients with hypocitraturic calcium stones. Design, Setting, Participants: This prospectively randomized controlled trial was conducted from January 2003 to December 2012. Patients aged over 40 years old, with a history of hypocitraturic calcium stones were eligible: of 347 patients, 101 were in the control group, and 102 patients were in the potassium citrate group. Baseline examinations and patient recruitment occurred in 2001. Intervention: Potassium citrate therapy consisted of Urocit®-K 60 mEq. per day. All patients met with a dietitian and were instructed to maintain a diet restricted to 2 g of sodium and 65 g of protein. The patients were asked to consume sufficient fluid to urinate ≥2 L daily. Main Outcome Measure: The primary outcome was mean change in urinary citrate level, measured throughout the entire follow-up period at an outpatient clinic for up to 10 years. Results: The final analysis included 101 (control) and 102 (Potassium citrate) patients. In the Potassium citrate group, mean urinary citrate levels increased from 197.8 (baseline) to 523.7 mg/day (9th year), with a response rate of 67.65% (P<0.001 vs. control). The stone recurrence rate ranged from 6.90% (1st year) to 68.32% (9th year) in the control group and from 2.94% (1st year) to 28.43% (9th year) in the potassium citrate group (P<0.001). Limitations: Enrolled patients was diagnosed complete stone free. The study cannot elucidate the role of residual fragments in the recurrent stones. Conclusions: Potassium citrate provides a significant alkali and citraturic response during long term therapy with a sustained change in urinary parameters. Moreover, long term potassium citrate therapy significantly decreases the stone formation rate, confirming usefulness in patients with hypocitraturic calcium stones.