STONE DISEASE

Effect of potassium citrate therapy on stone recurrence and residual fragments after shockwave lithotripsy in lower caliceal calcium oxalate urolithiasis: a randomized controlled trial
Soygur T, Akbay A, Kupeli S
Department of Urology, Faculty of Medicine, University of Ankara, Turkey
J Endourol. 2002; 16:149-52

• Background and Purpose: To evaluate the efficacy of potassium citrate treatment in preventing stone recurrences and residual fragments after shockwave lithotripsy (SWL) for lower pole calcium oxalate urolithiasis.
• Patients and Methods: One hundred ten patients who underwent SWL because of lower caliceal stones and who were stone free or who had residual stone 4 weeks later were enrolled in the study. The average patient age was 41.7 years. All patients had documented simple calcium oxalate lithiasis without urinary tract infection and with normal renal morphology and function. Four weeks after SWL, patients who were stone free (N = 56) and patients who had residual stones (N = 34) were independently randomized into two subgroups that were matched for sex, age, and urinary values of citrate, calcium, and uric acid. One group was given oral potassium citrate 60 mEq per day, and the other group served as controls.
• Results: In patients who were stone free after SWL and receiving medical treatment, the stone recurrence rate at 12 months was 0 whereas untreated patients showed a 28.5% stone recurrence rate (P < 0.05). Similarly, in the residual fragment group, the medically treated patients had a significantly greater remission rate than the untreated patients (44.5 v 12.5%; P < 0.05).
• Conclusion: Potassium citrate therapy significantly alleviated calcium oxalate stone activity after SWL for lower pole stones in patients who were stone free. An important observation was the beneficial effect of medical treatment on stone activity after SWL among patients with residual calculi.
  
  
• Editorial Comment
  A previous retrospective study by Fine and colleagues (1) demonstrated the benefit of medical therapy in reducing the rate of stone recurrence in both groups of patients, those rendered stone-free and those with residual stone fragments after shock wave lithotripsy (SWL). The authors of the current study evaluated specifically, in a prospective randomized trial, the efficacy of potassium citrate therapy in reducing stone recurrence or regrowth in patients undergoing SWL for lower calyceal stones. A total of 90 patients, including 56 stone-free patients and 34 patients with residual fragments, were randomized to receive either 60 mEq of potassium citrate daily or no treatment, 4 weeks after undergoing SWL for lower pole stones. After 12 months, all patients were evaluated with plain abdominal radiographs and ultrasound. Among the stone-free patients, no stone recurrences occurred in those treated with potassium citrate, while 28.5% of control patients experienced recurrence. Among the patients with residual fragments, 45.5% demonstrated clearance of the fragments during follow-up, and the remaining 54.5% of patients showed no stone growth or recurrence. In the control group, however, only 12.5% of patients cleared their residual fragments, 25% of patients showed no change in the size of the stones, and 62% demonstrated stone growth.
  This important study validates in a prospective trial the retrospective findings of Fine and associates by demonstrating that medical therapy, specifically potassium citrate, reduces the rate of stone recurrence or stone growth in both group of patients rendered stone-free or left with residual fragments after SWL. Of additional interest, potassium citrate also apparently facilitated the discharge of residual lower pole fragments in patients with residual stones. Consequently, adjuvant medical therapy after SWL may actually improve stone free rates by encouraging fragment clearance. If this is indeed the case, the administration of potassium citrate immediately after, or even before, SWL may prove to be efficacious. Interestingly, potassium citrate appeared to be effective in a variety of metabolic backgrounds, although stratification of outcomes by urinary biochemical abnormality was not performed. With further study, short- or long-term potassium citrate treatment of patients undergoing SWL may prove beneficial.

Reference
1. Fine JK, Pak CYC, Preminger GM: Effect of medical management and residual fragments on recurrent stone formation following shock wave lithotripsy. J Urol. 1995; 153:27-32.

Dr. Margaret S. Pearle
Associate Professor of Urology
University of Texas Southwestern Med Ctr
Dallas, Texas, USA