1190 STONE FRAGMENTS AFTER EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY

12. h e , J. K, Pak, C. Y. C. and F’reminger, G. M.: Effect of medical management and residual fragments on merit stone for- mation following shock wave lithotripsy. J. Urol., 159: 27, 1995.

EDITORIAL COMMENT Many of us recall the scenario: you are performing open nephro-

lithotomy to remove a large complex renal calculus and intraopera- tive radiographs demonstrate a 4 mm. fragment remaining in a lower pole calix. Although you are currently 3 hours into the case and sti l l have 2 more procedures to perform later that day, you spend the next hour frantically searching for the residual fragment. Although the patient wil l be symptomatically improved, you dread the thought of having to present this m e at the next x-ray conference and have it deemed a “failure.” Now, move ahead 15 years to the age of shock wave lithotripsy: 1 month after undergoing shock wave lithotripsy for a 1 an. renal pelvic stone the patient returns for followup radio- graphs and is found to have a 4 mm. residual fragment in the lower pole &. Many would consider this stone fragment to be “clinically insignificant” and subsequently deem the case “sucxessful.”

Therefore, one might ask why should we change our criteria for suaxss, although the modalities of stone removal have changed? No doubt the major advantage of shock wave lithotripsy is its minimally invasive nature and ability to treat the majority of renal calculi with symptomatic success. However, since the incidence of residual frag- ments following shock wave lithotripsy remains fairly high, the term clinically insignificant residual fragments has crept into our vocab- ulary as a means to justify the pesky residual fragments that remain after treatment. A number of studies have recently suggested that residual hgments following lithotripsy or any other type of stone removal may cause a significant risk for growth or induction of recurrent &one formation.

The present study strongly supports the notion that the term c l i n i d y insignificant fragments may in fact be a misnomer. In this review of a large number of patients who underwent successful shock wave lithotripsy but had noninfected stone fragments of less than 5 mm. more than 40% of the patients eventually became symptomatic or required intervention when followed for an average of 26 months. Indeed, Kaplan-Meier estimates predicted the probability of symp- tomatic episodes or the need for intervention to be greater than 70% if there was a small residual fragment and followup was more than 5 years after shock wave lithotripsy. The authors should be congrat- ulated for confirming the potential problems inherent in leaving residual stone fragments behind no matter what modality is used for treating symptomatic renal calculi. As suggested, patients with posttreatment residual stones require

persistent surveillance and they should be informed of the potential

for continuing problems from residual fragments. Furthermore, pre- vious studies suggest that adjunct medical therapy may facilitate the p a s w e of retained fragments as well as inhibit the growth of resid- ual calculi or the formation of new stones. merefore, we believe that all attempts should be made to render a patient stone-free to avoid the incidence of residual fragments (references 11 and 12 in article). stonefree status can be best achieved by selecting the most appro. priate treatment alternative for the management of a stone of a p h c d a r size, composition or location (that is a percutaneous ap- proach for a 1.5 cm. calcium oxalate monohydrate stone in the lower pole). Auxiliary medical therapy can be a useful adjunct to reduce the risk of residual stone growth or new Stone formation a h r shock wave lithotripsy or any other form of surgical stone removal.

Glenn M. Preminger Division of Urology Dlrke ffnzuersity Medical Center Durham, North Carolina

REPLY BY AUTHORS The consequences of leaving a stone after operative intervention in

the pre-ESWL era were certainly different than those today. While we found that a significant number of patients with post-ESm residual fragments will suffer symptomatic episodes or require in- tervention, the intervention required will be relatively noninvasive and consist of either repeat ESWL or retrograde endoscopy. There- fore, we believe that appropriate management of small, asymptom- atic post-ESWL calcium oxalate or calcium phosphate stone frag- ments is expectant. Rather than submit all such patients to further and perhaps more invasive intervention in an attempt to render them stone-free, secondary procedures can be applied selectively to those who have significant symptoms or obstruction associated with the residual stone.

Medical therapy is unlikely to have a significant impact on the incidence of symptomatic episodes resulting from residual calcium oxalate or calcium phosphate fragments, since there is little evidence that such fragments can be dissolved. However, an advantage of decreasing the growth of such fragments with specific medical ther- apy seems obvious, although even this remains unproved. We agree that patients with recurrent calculi should be offered an evaluation for predisposing metabolic abnormalities and, when such abnormal- ities are identified, specific medical treatment should be instituted. The impact of such medical therapy on the rate of new stones or stone growth, or the ultimate need for further intervention in pa- tients with residual stones versus those rendered stone-free is an area worthy of prospective study.