MEDICAL MANAGEMENT AND RESIDUAL FRAGMENT EFFECTS ON STONE FORMATION 33

sures, such as treatment with thiazides for years, it appears rather unlikely that compliance was always perfect. Unfortunately, the authors provide no data on how compliance was monitored during the observation period, and if the underlying metabolic and environ- mental defects were indeed corrected. Moreover, were the patients in the control group really drinking enough fluids and avoiding dietary excesses, although they discontinued medical therapy? Without clear answers to these questions, this is just another study of the many conflicting reports on this topic. Using almost identical methods, albeit a longer observation period and more detailed followup exam- inations, a recent study from our metabolic unit failed to show a benefit of medical therapy in patients with hypercalciuria, hypercit- raturia and/or hyperuric~suria.~

It appears imperative to adopt the guidelines for study design considered standard in uro-oncology or in the treatment of benign prostatic hyperplasia also for urolithiasis. Retrospective, poorly con- trolled studies must be abandoned in favor of prospective, random- ized trials with clearly defined control groups. Otherwise, this dis- cussion will continue undecided also in the next decades.

The authors are to be applauded, however, for demonstrating the inherent risk of growth of residual fragments after ESWL. These patients cannot be considered successfully treated, and close surveil- lance and, possibly, treatment are needed.

Michael Marberger Urologische Klinik Der Universitat Wien Wien, Austria

1. Ryall, R. L. and Marshall, V. R.: The value of the 24 hour urine analysis in the assessment of stone-formers attending a gen- eral hospital outpatient clinic. Brit. J. Urol., 5 5 1, 1983.

2. Tiselius, H. G., Almgard, L. E., Larson, L. and Sorbo, B.: A biochemical basis for grouping of patients with urolithiasis. Eur. Urol., 4 241, 1978.

3. Welshman, S. G. and McGeown, M. G.: Urine citrate excretion in stone formers and normal controls. Brit. J. Urol., 4 8 7, 1976.

4. Hobarth, K., Hofbauer, J. and Szabo, N.: Value of repeated analyses of 24-hour urine in recurrent calcium urolithiasis. Urology, 44: 20, 1994.

REPLY BY AUTHORS

We believe that our article has raised and, perhaps, clarified 2 important issues regarding patients treated with shock wave litho- tripsy. The first point is that residual stone fragments left behind after shock wave lithotripsy may increase in size. The previously coined term, "clinically insignificant residual fragments" may indeed be a misnomer. We agree with Doctor Segura that residual frag-

ments should be avoided and that alternative therapies, such as percutaneous stone removal or a ureteroscopic approach, may be more appropriate in complex stone disease to reduce the incidence of residual stone material.

The second major point of our study was to demonstrate that appropriate metabolic evaluation combined with selective medical therapy can be a cost-effective option in treating patients with nephrolithiasis. As Doctor Marberger suggests, it is often difficult if not impossible to assess fully the impact of medical therapy on recurrent stone disease due to problems with followup, patient com- pliance, difficulty obtaining reliable data and so forth. We believe that our study is unique since all patients were evaluated at the same metabolic stone center, followed by the same physicians and personally contacted for followup. Yet we understand the limitations of this retrospective study and support the suggestion that a large prospective randomized trial should be performed to discern the impact of medical therapy on patients with stone disease.

However, methodological and ethical problems exist in randomiz- ing metabolically active stone formers into placebo-controlled trials while appropriate medical treatment can significantly impact the incidence of recurrent stone formation. There have been a small number of prospective randomized studies that have demonstrated the beneficial affects of medical therapy to prevent recurrent stone disease.'-5 Therefore, we believe that the results of our study are valid. One should assess the nature and severity of stone formation in individuals, and institute appropriate metabolic therapy, if indi- cated. With this approach the urologist can offer stone forming patients a relatively simple, effective and cost conscious alternative to recurrent surgical stone removal.

REFERENCES

1. Ettinger, B.: Recurrence of nephrolithiasis. A six-year prospec- tive study. Amer. J. Med., 67: 245, 1979.

2. Smith, M. J.: Placebo versus allopurinol for renal calculi. J. Urol., 117: 690, 1977.

3. Griffith, D. P., Gleeson, M. J., Lee, H., Longuet, R., Deman, E. and Earle, N.: Randomized, double-blind trial of Lithostat (acetohydroxamic acid) in the palliative treatment of infection- induced urinary calculi. Eur. Urol., 2 0 243,1991.

4. Barcelo, P., Wuhl, O., Servitge, E., Rowaud, A. and Pak, C. Y. C.: Randomized double-blind study of potassium citrate in idio- pathic hypoctiraturic calcium nephrolithiasis. J. Urol., 150. 1761, 1993.

5. Cicerello, E., Merlo, F., Gambaro, G., Meccatrozzo, L., Fandella, A., Baggio, B. and Anselmo, G.: Effect of alkaline citrate ther- apy on clearance of residual renal stone fragments after ex- tracorporeal shock wave lithotripsy in sterile calcium and in- fection nephrolithiasis patients. J. Urol., 151: 5, 1994.