Dissolution of residual microfragments with citrate therapy after extracorporeal shock wave lithotripsy

Residual microfragments after ESWL were studied for their presence and for possibility of dissolution with citrate therapy. Among 123 patients with renal stones who became stone-free following ESWL, a computed tomogram (CT) identified remaining microfragments within the treated kidney in 31.7% of the patients, even though stone fragments were not detectable on ordinary x-ray (KUU). The experiments, in which calcium oxalate stone fragments collected after ESWL were incubated in buffer solutions with citrate 0 to 4 mmol/L, showed that citrate dissolved the stone fragments. Using human urine as a solution, the dissolving effect was greater in spot urines after alkali citrate administration than in control urines. Eighteen patients with microfragments underwent a follow-up CT 3 months later. The results showed that the microfragments had disappeared in 6 of 11 (54.5%) patients who had been taking alkali citrate, whereas microfragments remained unchanged in all 5 patients without medication. Our results suggest that citrate therapy would be advisable as a prophylaxis for stone recurrence especially after ESWL treatment.