- Email: [email protected]
SIMULTANEOUS VERSUS STAGED BILATERAL EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY: LONG-TERM EFFECT ON RENAL FUNCTION
0022-5347/99/162fj-1.i9110
THEJOCKNAI. OF UROLOGY
Vol. 162,1591-1593,November 1999 Printed in U S A .
Copyright 0 1999 by AMERICANURoLoCICAL A~SOCIATION, Ih'c
SIMULTANEOUS VERSUS STAGED BILATERAL EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY: LONG-TERM EFFECT ON RENAL FUNCTION ANDREW J. PIENKNY
AND
STEVAN B. STREEM*
From the Department of Urology, Cleveland Clinic Foundation, Cleweland, Ohio
ABSTRACT
Purpose: We determine whether there is a clinically significant difference in the long-term effect on renal function following simultaneous versus staged bilateral extracorporeal shock wave lithotripsy (ESWLt). Materials and Methods: Between July 1986 and October 1995, 360 patients underwent treatment for bilateral renal calculi with ESWL using a Dornier HM-3 lithotriptor. Of the patients 319 had both kidneys treated simultaneously (simultaneous group) and the remaining 4 1 were treated in a planned, staged fashion (staged group) with the procedures separated by 3 to 20 weeks (mean 6.0). Followup data of at least 1 year were available for 49 men and 30 women (mean age 52.4) in the simultaneous group, and 8 and 12 (mean age 45.1), respectively, in the staged group. Mean stone burden was 0.70 cm.2 on the right and 0.87 on the left side in the simultaneous group, and 1.6 and 1.5, respectively, in the staged group. Results: Patients with a t least 1calculus greater than 0.5 cm.' treated simultaneously received a mean of 1,386 shock waves to the right and 1,637 to the left side, and the staged group received a mean of 1,802 and 2,094, respectively. Mean serum creatinine was 1.03 mg./dl. before and 1.04 after treatment (normal 0.7 to 1.4 mg./dl.) in the simultaneous group, representing a mean increase of 0.01 at followup of 1.0 to 10.5 years (mean 3.7), and 0.88 and 0.88, respectively, in the staged group, representing a decrease of 0.005 at followup of 1.0 to 7.2 years (mean 3.2). The effects of simultaneous versus staged ESWL on renal function as measured by serum creatinine were not statistically significant using a multiple regression model which controlled for the effects of stone burden, number of shock waves, patient age, pretreatment serum creatinine and length of followup (p = 0.19). Conclusions: There is no clinically apparent difference in the long-term effect on renal function for patients with bilateral renal calculi treated with ESWL in a simultaneous versus staged fashion. KEY WORDS:lithotripsy, kidney calculi, creatinine, treatment outcome Most oatients with bilateral renal calculi are amenable to treatment with extracorporeal shock wave lithotripsy (ESWL) but limited data are available to suggest whether they should be treated in a simultaneous or staged fashion. Cass reported bilateral simultaneous treatment to be safe in a small group of patients with normal pretreatment renal function.' However, Thomas et a1 showed a short-term decrease in estimated renal plasma flow following simultaneous bilateral treatment and recommended proceeding "cautiously with simultaneous bilateral treatment."2 We determine whether there is a clinically significant difference in the long-term effect on renal function following simultaneous versus staged bilateral ESWL. PATIENTS AND METHODS
Between July 1986 and October 1995,360 patients underwent treatment for bilateral renal calculi with ESWL on a Dornier HM-3 lithotriptor. Of these patients 319 had both kidneys treated simultaneously (simultaneous group) and
the remaining 41 were treated in a planned, staged fashion (staged group) with procedures separated by 3 20 weeks (mean 6.0). Serum creatinine was measured before ESWL in all cases. Followup data of a t least 1year were available for 79 simultaneous (25%)and 20 staged (50%)cases. The simultaneous group included 49 male and 30 female patients 1.4 to 77 years old (mean age 52.4) and the staged group included 8 and 12, respectively, 21 to 61 years old (mean age 45.1). Stone burden was 0.04 to 3.0 (mean 0.70) on the right and 0.04 t o 4.0 (mean 0.87) on the left side in the simultaneous group, and 0.2 to 4.6 (mean 1.6)and 0.1 to 4.0 (mean 1.5), respectively, in the staged group. Differences between the 2 treatment groups with respect to individual patient, stone and treatment characteristics were compared using the 2 sample t-test for independent samples. Differences between pretreatment and posttreatment serum creatinine levels within a treatment group were analyzed using the 1-sample t test for paired data. The treatment groups differed with respect to a number of important characteristics and, therefore, multiple linear regression models were used to evaluate the effect of treatment group while controlling for the possible effects of differences in patient, stone and treatment characteristics, and length of followup (table 1). Right and left stone burdens were 0.5 cm.' or less in 23 simultaneous and 1staged cases. These patients tended to be younger and received significantly fewer shock waves than
Accepted for publication May 14, 1999. * Requests for reprints: Department of Urology, A 100, Cleveland clinic Foundation, 9500 Euclid Ave., Cleveland, Ohio 44195. I Dornier Medical Systems, Inc., Marietta, Georgia. Editor's Note: This article is the second of 5 published in this issue for which category 1 CME credits can be earned. Instructions for obtaining credits are given with the questions on pages 1760 and 1761. 1591
1592
LONG-TERM EFFECT OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY ON RENAL FUNCTION
TABLE1. Patients with at least 1 stone greater than 0.5 em.' CharaaeriStiC
Simultaneous Treatment
staged
P Value
Treatment
19 No. pts. 56 Mean age 2 SD at ESWL 53.1 2 12.5 44.5 ? 9.9 Mean pre-ESWL creatinine 2 SD 1.03 2 0.27 0.88 ir 0.17 Mean post-ESWL creatinine 2 SD 1.04 2 0.27 0.88 f 0.18 Mean change creatinine 2 SD 0.01 2 0.24 -0.005 f 0.17 Rt. kidney: Mean stone burden 2 SD (cm.2) 0.9 2 0.80 1.6 2 1.09 Mean shock waves 2 SD 1,386 2 648 1,8022 534 Lt. kidney: Mean stone burden 2 SD ( c m Z ) 1.5 2 1.04 1.1 2 0.91 Mean shock waves 2 SD 2,094 ? 639 1,637ir 667 Mean followup f SD (yrs.) 3.2 ? 1.75 3.7 ir 2.19
0.004 0.009 0.01 0.78 0.02 0.009 0.13 0.01 0.38
after ESWL for these 16 matched pairs of patients was -0.08 5 0.21 mg./dl. (range -0.20 to 0.70),which was not s t a t i s t i d y signiscant (p = 0.18). Of the 79 simultaneous group patients 7 (8.9%)required secondary ESWL for residual calculi in 8 renal units (5.1%). Of the 20 staged group patients 5 (25%)required secondary ESWL in 5 renal units (12.5%).Complications developed in 7 simultaneous group patients (8.9%),and included pain requiring hospital admission for intravenous hydration and analgesia in 2, perirenal hematoma managed conservatively in 3 and post-ESWL endoscopic manipulation in 2. Of the 20 staged group patients 1 had a complication (5%)which required post-ESWL endoscopic manipulation. DISCUSSION
those with stone burdens greater than 0.5 cm.2 Consequently, the majority of statistical comparisons were performed on the 56 simultaneous and 19 staged cases with a stone burden of greater than 0.5 cm? on a t least 1 side. Because a major end point of this study was effect on renal function as determined by serum creatinine, we also performed a separate analysis of patient pairs exactly matched for pre-ESWL serum creatinine, and age and total number of shock waves. RESULTS
Patient, stone and treatment characteristics of the 75 patients with right or leR stone burden greater than 0.5 cm.' are summarized in table 1. The simultaneous group received 300 to 2,700 shock waves (mean 1,386)to the right and 400 to 2,850 (mean 1,637) to the left kidney, and the staged group received 600 to 2,500 (mean 1,802) and 500 to 3,000 (mean 2,094), respectively. All shock waves were delivered at 18 to 22 kV. Serum creatinine (normal 0.7 to 1.4) ranged from 0.7 to 1.9 mg./dl. (mean 1.03) before and 0.6 to 1.7 (mean 1.04) aRer ESWL in the simultaneous group, representing a mean increase of 0.01 at followup of 1.0 to 10.5 years (mean 3.7), and from 0.6 to 1.2 (mean 0.88) and 0.6 to 1.2 (mean 0.88), respectively, in the staged group, representing a mean decrease of 0.005 at followup of 1.0 to 7.2 years (mean 3.2). The difference in mean changes in serum creatinine at long-term followup within each group was not significant (p = 0.78 and 0.89). The simultaneous group differed significantly from the staged group (table 1). Patients treated simultaneously tended to be older, had higher pretreatment serum creatinine and smaller stone burdens, and received fewer shock waves. Multiple linear regression models were used to compare the 2 groups which controlled for differences in stone burden, number of shock waves, age, pretreatment serum creatinine and length of followup. Adjusting for the effects of these other factors, treatment group (simultaneous versus staged) did not impact the long-term effect on renal function, which was not significantly different (p = 0.19). Due to the difference in pretreatment serum creatinine between the 2 groups, we also selected a subgroup matched for exact pretreatment serum creatinine, age and total number of shock waves (table 2). Mean difference in the change in serum creatinine before and TABLE2 . Patient pairs matched for pre-ESWL serum creatinine
No. pta. Mean age SD (yrs.) Mean shock waves 2 SD Mean pretreatment serum creatinine t SD (mgldl.) Mean posttreatment serum creatinine ? SD (mgJdl.) Change in serum creatinine p = 0.18.
Simultaneous Group
Staged Group
16 44.2 2 10.8 3,865 2 945 0.9 2 0.16
16 47.52 7.3 3,634 2 734 0.9 2 0.16
0.9 2 0.17
1.0 2 0.21
ESWL is the standard treatment for most patients requiring intervention for renal and upper ureteral calculi. Previous studies have evaluated the short and long-term effects of ESWL on renal function in solitary kidneys. h l s e n and Berg found no change in serum creatinine 24 and 48 hours after ESWL, although they noted a significant decrease in inulin clearance and increase in urinary excretion of p-2 microglobulin, suggesting an element of renal tubular dysf u n ~ t i o nKulb . ~ et a1 demonstrated no significant change in serum creatinine or effective renal plasma flow 3 months following ESWL to a solitary kidney? However, Chandhoke et a1 demonstrated a 22%reduction in glomerular filtration rate in patients with a solitary kidney or compromised renal function (serum creatinine greater than 2.0 mg./dl.) treated with ESWL and followed for a mean of 42 month^.^ Cass also showed a 22%reduction in glomerular filtration rate in patients with solitary kidneys followed for greater than 24 months after ESWL.' In contrast, Zanetti et a1 found no long-term adverse effect on serum creatinine after a followup of 24 to 56 months7 Effects of ESWL on solitary kidneys may be extrapolated to some extent and applied to simultaneous treatment of bilateral renal calculi. However, few studies have examined these effects directly. We evaluated the long-term changes in serum creatinine in patients with bilateral renal calculi treated with simultaneous or staged ESWL, as the renal functional effects of these alternative treatment strategies have been an area of controversy. In each group there was no significant effect of ESWL on serum creatinine at a mean followup of 3.7 and 3.2 years, respectively. However just as importantly, with a mean followup of approximately 3.5 years in both groups, there was no significant difference in effect on overall renal function as determined by serum creatinine. Our treatment groups were not randomized, and they differed significantly with regard to age, stone burden and number of shock waves. Patients with a larger stone burden tended to be treated in a staged fashion, due to an assumption that they would more likely require secondary treatment anyway and for fear of even temporary bilateral obstruction which could occur with simultaneous treatment. Our complication and re-treatment rates were within previously reported ranges for ESWL,'s9 and the higher rate of retreatment in the staged group likely reflects this greater stone burden. For this reason a multiple linear regression analysis was performed to control for the possible effects of different patient, stone and treatment characteristics, and there was still no significant difference in effect on renal function between treatment groups. Similarly, even when a subset of patients matched for exact pretreatment serum creatinine were compared no significant difference in effect on renal function was seen. CONCLUSIONS
Several factors, including overall stone burden, co-morbid medical problems, differential and overall renal function, and
LONG-TERM EFFECT OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY ON RENAL FUNCTION
individual anatomy, are generally considered when determining whether patients should undergo simultaneous versus staged bilateral ESWL, and this study should not be taken as advocation or justification for 1approach in favor of the other. Rather, some patients with bilateral calculi at presentation will require shock wave lithotripsy to both kidneys, and few studies have addressed the differences in longterm renal function between simultaneous and staged bilateral treatments. Furthermore, the few available reports have offered conflicting results. We found no significant difference in the long-term effect on renal function after simultaneous or staged bilateral ESWL, or significant difference in effect on long-term renal function between treatment regimens. Thus, when determining whether an individual patient should undergo simultaneous versus staged bilateral treatment, several factors should be considered. However, our study suggests that a difference in long-term effect on renal function need not be 1of those factors. REFERENCES
1. Cass, A.S.:Long-term renal function after bilateral extracorporeal shock wave lithotripsy. J. Endourol., 6 19,1992. 2. Thomas, R., Roberts, J., Sloane, B. and Kaack, B.: Effect of extracorporeal shock wave lithotripsy on renal function. J. Endourol., 2 141,1988.
1593
3. Karlsen, S.J. and Berg, K. J.: Acute changes in renal function following extracorporeal shock wave lithotripsy in patients with a solitary functioning kidney. J. Urol., 145 253, 1991. 4. Kulb, T.B.,Lingeman, J. E., Coury, T. A,, Steele, R. E., Newman, D. M, Mertz, J. M., Mosbaugh, P. G. and Knapp, P.: Extracorporeal shock wave lithotripsy in patients with a solitary kidney. J. Urol., 136 786,1986. 5. Chandhoke, P.S., Abala, D. M. and Clayman, R. V.: Long-term comparison of renal hnction in patients with solitary kidneys andlor moderate renal insufficiency undergoing extracorporeal shock wave lithotripsy or percutaneous nephrolithotomy. J. Urol., 147: 1226,1992. 6. Cass, A. S.:Renal function after extracorporeal shock wave lithotripsy to a solitary kidney. J. Endourol., 8 15, 1988. 7. Zanetti, G. R., Montanan, E., Guameri, A,, Trinchieri, A,, Mandressi, A and Ceresoli, A,: Long-term followup after extracorporeal shock wave lithotripsy treatment of kidney stones in solitary kidneys. J. Urol., 148 1011,1992. 8. Drach, G. W., Dretler, S., Fair, W., Finlayson, B., Gillenwater, J., Griffith, D., Lingeman, J. and Newman, D.: Report of the United States Cooperative Study of Extracorporeal Shock Wave Lithotripsy. J. Urol., 135 1127,1986. 9. Lingeman, J. E., Newman, D. M., Mertz, J. H. O., Mosbaugh, P. G., Steele, R. E., Kahnoski, R. J., Coury, T. A. and Woods., J. R.: Extracorporeal shock wave lithotripsy: the Methodist Hospital of Indiana experience. J. Urol., 135 1134,1986.
THEJOCKNAI. OF UROLOGY
Vol. 162,1591-1593,November 1999 Printed in U S A .
Copyright 0 1999 by AMERICANURoLoCICAL A~SOCIATION, Ih'c
SIMULTANEOUS VERSUS STAGED BILATERAL EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY: LONG-TERM EFFECT ON RENAL FUNCTION ANDREW J. PIENKNY
AND
STEVAN B. STREEM*
From the Department of Urology, Cleveland Clinic Foundation, Cleweland, Ohio
ABSTRACT
Purpose: We determine whether there is a clinically significant difference in the long-term effect on renal function following simultaneous versus staged bilateral extracorporeal shock wave lithotripsy (ESWLt). Materials and Methods: Between July 1986 and October 1995, 360 patients underwent treatment for bilateral renal calculi with ESWL using a Dornier HM-3 lithotriptor. Of the patients 319 had both kidneys treated simultaneously (simultaneous group) and the remaining 4 1 were treated in a planned, staged fashion (staged group) with the procedures separated by 3 to 20 weeks (mean 6.0). Followup data of at least 1 year were available for 49 men and 30 women (mean age 52.4) in the simultaneous group, and 8 and 12 (mean age 45.1), respectively, in the staged group. Mean stone burden was 0.70 cm.2 on the right and 0.87 on the left side in the simultaneous group, and 1.6 and 1.5, respectively, in the staged group. Results: Patients with a t least 1calculus greater than 0.5 cm.' treated simultaneously received a mean of 1,386 shock waves to the right and 1,637 to the left side, and the staged group received a mean of 1,802 and 2,094, respectively. Mean serum creatinine was 1.03 mg./dl. before and 1.04 after treatment (normal 0.7 to 1.4 mg./dl.) in the simultaneous group, representing a mean increase of 0.01 at followup of 1.0 to 10.5 years (mean 3.7), and 0.88 and 0.88, respectively, in the staged group, representing a decrease of 0.005 at followup of 1.0 to 7.2 years (mean 3.2). The effects of simultaneous versus staged ESWL on renal function as measured by serum creatinine were not statistically significant using a multiple regression model which controlled for the effects of stone burden, number of shock waves, patient age, pretreatment serum creatinine and length of followup (p = 0.19). Conclusions: There is no clinically apparent difference in the long-term effect on renal function for patients with bilateral renal calculi treated with ESWL in a simultaneous versus staged fashion. KEY WORDS:lithotripsy, kidney calculi, creatinine, treatment outcome Most oatients with bilateral renal calculi are amenable to treatment with extracorporeal shock wave lithotripsy (ESWL) but limited data are available to suggest whether they should be treated in a simultaneous or staged fashion. Cass reported bilateral simultaneous treatment to be safe in a small group of patients with normal pretreatment renal function.' However, Thomas et a1 showed a short-term decrease in estimated renal plasma flow following simultaneous bilateral treatment and recommended proceeding "cautiously with simultaneous bilateral treatment."2 We determine whether there is a clinically significant difference in the long-term effect on renal function following simultaneous versus staged bilateral ESWL. PATIENTS AND METHODS
Between July 1986 and October 1995,360 patients underwent treatment for bilateral renal calculi with ESWL on a Dornier HM-3 lithotriptor. Of these patients 319 had both kidneys treated simultaneously (simultaneous group) and
the remaining 41 were treated in a planned, staged fashion (staged group) with procedures separated by 3 20 weeks (mean 6.0). Serum creatinine was measured before ESWL in all cases. Followup data of a t least 1year were available for 79 simultaneous (25%)and 20 staged (50%)cases. The simultaneous group included 49 male and 30 female patients 1.4 to 77 years old (mean age 52.4) and the staged group included 8 and 12, respectively, 21 to 61 years old (mean age 45.1). Stone burden was 0.04 to 3.0 (mean 0.70) on the right and 0.04 t o 4.0 (mean 0.87) on the left side in the simultaneous group, and 0.2 to 4.6 (mean 1.6)and 0.1 to 4.0 (mean 1.5), respectively, in the staged group. Differences between the 2 treatment groups with respect to individual patient, stone and treatment characteristics were compared using the 2 sample t-test for independent samples. Differences between pretreatment and posttreatment serum creatinine levels within a treatment group were analyzed using the 1-sample t test for paired data. The treatment groups differed with respect to a number of important characteristics and, therefore, multiple linear regression models were used to evaluate the effect of treatment group while controlling for the possible effects of differences in patient, stone and treatment characteristics, and length of followup (table 1). Right and left stone burdens were 0.5 cm.' or less in 23 simultaneous and 1staged cases. These patients tended to be younger and received significantly fewer shock waves than
Accepted for publication May 14, 1999. * Requests for reprints: Department of Urology, A 100, Cleveland clinic Foundation, 9500 Euclid Ave., Cleveland, Ohio 44195. I Dornier Medical Systems, Inc., Marietta, Georgia. Editor's Note: This article is the second of 5 published in this issue for which category 1 CME credits can be earned. Instructions for obtaining credits are given with the questions on pages 1760 and 1761. 1591
1592
LONG-TERM EFFECT OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY ON RENAL FUNCTION
TABLE1. Patients with at least 1 stone greater than 0.5 em.' CharaaeriStiC
Simultaneous Treatment
staged
P Value
Treatment
19 No. pts. 56 Mean age 2 SD at ESWL 53.1 2 12.5 44.5 ? 9.9 Mean pre-ESWL creatinine 2 SD 1.03 2 0.27 0.88 ir 0.17 Mean post-ESWL creatinine 2 SD 1.04 2 0.27 0.88 f 0.18 Mean change creatinine 2 SD 0.01 2 0.24 -0.005 f 0.17 Rt. kidney: Mean stone burden 2 SD (cm.2) 0.9 2 0.80 1.6 2 1.09 Mean shock waves 2 SD 1,386 2 648 1,8022 534 Lt. kidney: Mean stone burden 2 SD ( c m Z ) 1.5 2 1.04 1.1 2 0.91 Mean shock waves 2 SD 2,094 ? 639 1,637ir 667 Mean followup f SD (yrs.) 3.2 ? 1.75 3.7 ir 2.19
0.004 0.009 0.01 0.78 0.02 0.009 0.13 0.01 0.38
after ESWL for these 16 matched pairs of patients was -0.08 5 0.21 mg./dl. (range -0.20 to 0.70),which was not s t a t i s t i d y signiscant (p = 0.18). Of the 79 simultaneous group patients 7 (8.9%)required secondary ESWL for residual calculi in 8 renal units (5.1%). Of the 20 staged group patients 5 (25%)required secondary ESWL in 5 renal units (12.5%).Complications developed in 7 simultaneous group patients (8.9%),and included pain requiring hospital admission for intravenous hydration and analgesia in 2, perirenal hematoma managed conservatively in 3 and post-ESWL endoscopic manipulation in 2. Of the 20 staged group patients 1 had a complication (5%)which required post-ESWL endoscopic manipulation. DISCUSSION
those with stone burdens greater than 0.5 cm.2 Consequently, the majority of statistical comparisons were performed on the 56 simultaneous and 19 staged cases with a stone burden of greater than 0.5 cm? on a t least 1 side. Because a major end point of this study was effect on renal function as determined by serum creatinine, we also performed a separate analysis of patient pairs exactly matched for pre-ESWL serum creatinine, and age and total number of shock waves. RESULTS
Patient, stone and treatment characteristics of the 75 patients with right or leR stone burden greater than 0.5 cm.' are summarized in table 1. The simultaneous group received 300 to 2,700 shock waves (mean 1,386)to the right and 400 to 2,850 (mean 1,637) to the left kidney, and the staged group received 600 to 2,500 (mean 1,802) and 500 to 3,000 (mean 2,094), respectively. All shock waves were delivered at 18 to 22 kV. Serum creatinine (normal 0.7 to 1.4) ranged from 0.7 to 1.9 mg./dl. (mean 1.03) before and 0.6 to 1.7 (mean 1.04) aRer ESWL in the simultaneous group, representing a mean increase of 0.01 at followup of 1.0 to 10.5 years (mean 3.7), and from 0.6 to 1.2 (mean 0.88) and 0.6 to 1.2 (mean 0.88), respectively, in the staged group, representing a mean decrease of 0.005 at followup of 1.0 to 7.2 years (mean 3.2). The difference in mean changes in serum creatinine at long-term followup within each group was not significant (p = 0.78 and 0.89). The simultaneous group differed significantly from the staged group (table 1). Patients treated simultaneously tended to be older, had higher pretreatment serum creatinine and smaller stone burdens, and received fewer shock waves. Multiple linear regression models were used to compare the 2 groups which controlled for differences in stone burden, number of shock waves, age, pretreatment serum creatinine and length of followup. Adjusting for the effects of these other factors, treatment group (simultaneous versus staged) did not impact the long-term effect on renal function, which was not significantly different (p = 0.19). Due to the difference in pretreatment serum creatinine between the 2 groups, we also selected a subgroup matched for exact pretreatment serum creatinine, age and total number of shock waves (table 2). Mean difference in the change in serum creatinine before and TABLE2 . Patient pairs matched for pre-ESWL serum creatinine
No. pta. Mean age SD (yrs.) Mean shock waves 2 SD Mean pretreatment serum creatinine t SD (mgldl.) Mean posttreatment serum creatinine ? SD (mgJdl.) Change in serum creatinine p = 0.18.
Simultaneous Group
Staged Group
16 44.2 2 10.8 3,865 2 945 0.9 2 0.16
16 47.52 7.3 3,634 2 734 0.9 2 0.16
0.9 2 0.17
1.0 2 0.21
ESWL is the standard treatment for most patients requiring intervention for renal and upper ureteral calculi. Previous studies have evaluated the short and long-term effects of ESWL on renal function in solitary kidneys. h l s e n and Berg found no change in serum creatinine 24 and 48 hours after ESWL, although they noted a significant decrease in inulin clearance and increase in urinary excretion of p-2 microglobulin, suggesting an element of renal tubular dysf u n ~ t i o nKulb . ~ et a1 demonstrated no significant change in serum creatinine or effective renal plasma flow 3 months following ESWL to a solitary kidney? However, Chandhoke et a1 demonstrated a 22%reduction in glomerular filtration rate in patients with a solitary kidney or compromised renal function (serum creatinine greater than 2.0 mg./dl.) treated with ESWL and followed for a mean of 42 month^.^ Cass also showed a 22%reduction in glomerular filtration rate in patients with solitary kidneys followed for greater than 24 months after ESWL.' In contrast, Zanetti et a1 found no long-term adverse effect on serum creatinine after a followup of 24 to 56 months7 Effects of ESWL on solitary kidneys may be extrapolated to some extent and applied to simultaneous treatment of bilateral renal calculi. However, few studies have examined these effects directly. We evaluated the long-term changes in serum creatinine in patients with bilateral renal calculi treated with simultaneous or staged ESWL, as the renal functional effects of these alternative treatment strategies have been an area of controversy. In each group there was no significant effect of ESWL on serum creatinine at a mean followup of 3.7 and 3.2 years, respectively. However just as importantly, with a mean followup of approximately 3.5 years in both groups, there was no significant difference in effect on overall renal function as determined by serum creatinine. Our treatment groups were not randomized, and they differed significantly with regard to age, stone burden and number of shock waves. Patients with a larger stone burden tended to be treated in a staged fashion, due to an assumption that they would more likely require secondary treatment anyway and for fear of even temporary bilateral obstruction which could occur with simultaneous treatment. Our complication and re-treatment rates were within previously reported ranges for ESWL,'s9 and the higher rate of retreatment in the staged group likely reflects this greater stone burden. For this reason a multiple linear regression analysis was performed to control for the possible effects of different patient, stone and treatment characteristics, and there was still no significant difference in effect on renal function between treatment groups. Similarly, even when a subset of patients matched for exact pretreatment serum creatinine were compared no significant difference in effect on renal function was seen. CONCLUSIONS
Several factors, including overall stone burden, co-morbid medical problems, differential and overall renal function, and
LONG-TERM EFFECT OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY ON RENAL FUNCTION
individual anatomy, are generally considered when determining whether patients should undergo simultaneous versus staged bilateral ESWL, and this study should not be taken as advocation or justification for 1approach in favor of the other. Rather, some patients with bilateral calculi at presentation will require shock wave lithotripsy to both kidneys, and few studies have addressed the differences in longterm renal function between simultaneous and staged bilateral treatments. Furthermore, the few available reports have offered conflicting results. We found no significant difference in the long-term effect on renal function after simultaneous or staged bilateral ESWL, or significant difference in effect on long-term renal function between treatment regimens. Thus, when determining whether an individual patient should undergo simultaneous versus staged bilateral treatment, several factors should be considered. However, our study suggests that a difference in long-term effect on renal function need not be 1of those factors. REFERENCES
1. Cass, A.S.:Long-term renal function after bilateral extracorporeal shock wave lithotripsy. J. Endourol., 6 19,1992. 2. Thomas, R., Roberts, J., Sloane, B. and Kaack, B.: Effect of extracorporeal shock wave lithotripsy on renal function. J. Endourol., 2 141,1988.
1593
3. Karlsen, S.J. and Berg, K. J.: Acute changes in renal function following extracorporeal shock wave lithotripsy in patients with a solitary functioning kidney. J. Urol., 145 253, 1991. 4. Kulb, T.B.,Lingeman, J. E., Coury, T. A,, Steele, R. E., Newman, D. M, Mertz, J. M., Mosbaugh, P. G. and Knapp, P.: Extracorporeal shock wave lithotripsy in patients with a solitary kidney. J. Urol., 136 786,1986. 5. Chandhoke, P.S., Abala, D. M. and Clayman, R. V.: Long-term comparison of renal hnction in patients with solitary kidneys andlor moderate renal insufficiency undergoing extracorporeal shock wave lithotripsy or percutaneous nephrolithotomy. J. Urol., 147: 1226,1992. 6. Cass, A. S.:Renal function after extracorporeal shock wave lithotripsy to a solitary kidney. J. Endourol., 8 15, 1988. 7. Zanetti, G. R., Montanan, E., Guameri, A,, Trinchieri, A,, Mandressi, A and Ceresoli, A,: Long-term followup after extracorporeal shock wave lithotripsy treatment of kidney stones in solitary kidneys. J. Urol., 148 1011,1992. 8. Drach, G. W., Dretler, S., Fair, W., Finlayson, B., Gillenwater, J., Griffith, D., Lingeman, J. and Newman, D.: Report of the United States Cooperative Study of Extracorporeal Shock Wave Lithotripsy. J. Urol., 135 1127,1986. 9. Lingeman, J. E., Newman, D. M., Mertz, J. H. O., Mosbaugh, P. G., Steele, R. E., Kahnoski, R. J., Coury, T. A. and Woods., J. R.: Extracorporeal shock wave lithotripsy: the Methodist Hospital of Indiana experience. J. Urol., 135 1134,1986.