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Safety of ungated shockwave lithotripsy in pediatric patients
Journal of Pediatric Urology (2009) 5, 119e121
Safety of ungated shockwave lithotripsy in pediatric patients Ahmed M. Shouman, Islam A. Ghoneim, Ahmed ElShenoufy, Ali M. Ziada* Division of Pediatric Urology, Aboul-Riche Children’s Hospital, Cairo University, Cairo, Egypt Received 30 July 2008; accepted 21 October 2008 Available online 21 November 2008
KEYWORDS ESWL; Pediatric; Ungated
Abstract Objective: Ungated extracorporeal shockwave lithotripsy (ESWL) in adults is associated with cardiac arrhythmias. We report on the safety and efficacy of this method for treatment of renal calculi in children. Patients and methods: Children under 14 years with radio-opaque renal stones were treated by ungated ESWL. Pre-treatment plain radiographs and intravenous urography and post-treatment ultrasonography and plain films were used to follow up clearance of fragments. All children were monitored for arrhythmias. Results: Thirty-seven children (28 males, nine females) with a median age of 5 years (range 2e14 years) underwent 69 ungated ESWL sessions for renal calculi. Nineteen children had stones located in the left kidney, 17 had stones located in the right kidney and one child had bilateral renal stones. The stone size ranged from 6 to 25 mm (mean 9.9 mm). Shockwave number ranged from 800 to 3650 (mean of 2500 shockwaves per session). All children underwent lithotripsy with a gradual incremental energy increase from 14 to 20 kV. No patient had cardiac arrhythmias or other intra-procedural complications. No patient required conversion to gated ESWL. The overall stone-free rate was 86%. Conclusion: The results suggest that ungated ESWL is safe in children under 14 years. The efficacy was comparable to that of gated ESWL from previously published series. ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction Since its introduction in 1980, ESWL has become the first therapeutic option in most cases of upper-tract urolithiasis, and the technique has been used for pediatric renal stones
* Corresponding author. Tel.: þ20 10 1001136; fax: þ1 619 996 8026. E-mail address: [email protected] (A.M. Ziada).
since the first report of success in 1986. ESWL is a safe and effective method of treatment of urinary calculi in adults. Established guidelines for the use of ESWL in the adult population are based on stone size and technique (i.e. gated); these guidelines have not been as clearly established for children [1e3]. Despite lack of pediatric ESWL guidelines, the safety and efficacy of the method have been documented in the pediatric population, being applied for infants and older children, with a high success rate [4,5]. ESWL can be gated
1477-5131/$34 ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2008.10.007
120
A.M. Shouman et al.
(synchronizing shockwaves to the patient’s R-waves on electrocardiogram) or ungated (unsynchronized to the patient’s electrocardiogram). The latter technique, although safe in most patients, has been associated with cardiac arrhythmias in up to 21% of adult patients [6]. The incidence of arrhythmias in children undergoing ungated ESWL has not been established. An initial series of eight patients suggest that ungated ESWL is safe and efficacious in patients younger than 18 years of age [7]. The aim of this work was to study the safety and efficacy of ungated ESWL of renal calculi in children.
Patients and methods Between May 2006 and May 2007, patients younger than 14 years of age undergoing ESWL for renal calculi were evaluated. A total number of 37 children underwent 69 ungated ESWL sessions for treatment of renal calculi. There were 28 males and nine females. Their age ranged from 2 to 14 years with a median age of 5 years. The patients were then categorized according to stone size and location. A total of 43 renal stones were treated ranging in size from 6 to 25 mm with a mean of 9.9 mm. Calculi were on the right side in 17 cases (46%), on the left side in 19 cases (51%), and bilateral in one case (3%). Twelve patients had a previous history of stone disease (32.4%). Six cases had multiple stones per renal unit. Our approach to these cases was to treat the obstructing stone first. All patients met our inclusion criteria which were: an age of 14 years or younger, radio-opaque renal stones up to 25 mm in diameter, favorable anatomy and no contraindication for ESWL (e.g. distal obstruction, PUJ obstruction, stone in a calyceal diverticulum, etc.). Exclusion criteria included radiolucent stones, stones larger than 25 mm in diameter, unfavorable anatomy, uremia, nonfunctioning renal units, severe untreated UTI and bleeding tendency. ESWL was considered successful if patients were rendered stone free as evidenced by lack of any visible fragments on post-ESWL KUB done 3 weeks post-treatment to allow for sufficient clearance. ESWL was also considered successful if residual stones after fragmentation and clearance were clinically insignificant residual fragments (CIRFs), defined as asymptomatic non-infectious and nonobstructive fragments smaller than 4 mm [8]. Unsuccessful ESWL was defined as lack of evidence of disintegration, fragmentation, or clearance after three sessions of ESWL as proven by plain KUB radiographs and abdominal ultrasound. The lithotriptor used was the Dornier electromagnetic Do Li S device with fluoroscopic localization. All procedures Table 1
were performed with the patient under general anesthesia using ketamine 1.5 mg/kg and midazolam 0.05 mg/kg. The medications used had no renal protective effect. The average duration of general anesthesia was 20 min with a range of 15 to 35 minutes. It is to be noted that the bilateral case had bilateral double-J stents inserted ureteroscopically prior to treatment. Treatment started on the left side (with a smaller stone burden) until cleared, followed by complete clearance of the right side. All patients were monitored for arrhythmias in addition to standard cardiac and vital sign monitoring in the ESWL suite and recovery room. No catheters were used for patients undergoing treatment. Infected patients were given perioperative antibiotics for 7 days, with no hospitalization. Data analysis included the total number of shockwaves, power setting, stone clearance (stone-free rate, CIRFs), retreatment rate and complications. Patients were evaluated 1 month post session with renal ultrasonography and plain KUB radiographs. A comparison of pre-treatment imaging (KUB and IVU) and post-treatment imaging (KUB and abdominal ultrasonography) was done to determine clearance of fragments. Stone-free versus CIRFs as well as the need for retreatment was decided 3 weeks post session.
Results Stones less than 1 cm in size showed a very good response to ESWL with excellent fragmentation and clearance on follow-up radiographs (93.8% stone-free rate, 6.2% CIRFs). As the stone size increased, the number of shockwaves and fluoroscopy time per session increased, stone-free rates decreased, and residual fragments requiring retreatment increased (Table 1). The number of shockwaves ranged from 800 to 3650 with an average of 2500 shockwaves per session. All children underwent lithotripsy with a gradual increment in energy from 14 to 20 kV. There was no impact of age, sex, side of the stone on the results of ESWL. The calyceal location of stones in pediatric patients, unlike adults, did not significantly affect stone-free rates. No significant difference was found in stone-free rates among lower calyceal stones and stones in different renal locations (Table 2). Both fluoroscopy time and number of shockwaves showed a proportional increase with increasing size of the stone yet without impact on the success rate. No patient had cardiac arrhythmias or other intra-procedural complications. No patient required conversion to gated ESWL. Of the patients who achieved a successful outcome, 23 (56.1%) required one session while 18 (43.1%) required two
Effect of stone size on the results of ESWL.
Stone size
Total no. of stones
<1 cm 1e2 cm >2 cm Total
16 20 7 43
na Z Not applicable.
Success Stone-free rate
CIRFs
15 17 5 37
1 1 2 4
(93.8%) (85%) (71.4%) (86%)
(6.2%) (5%) (28.6%) (9.3%)
Failure
Mean no. of sessions
0 2 (10%) 0 2 (4.7%)
1.2 1.9 2.8 na
Retreatment rates
3 (12.5%) 9 (35%) 6 (71%) 18
Mean no. of shockwaves
Mean fluoroscopy time (s)
2233 2746 3489 na
160 200 260 na
Ungated shockwave lithotripsy Table 2
121
Effect of stone location on ESWL.
Stone calyceal location Renal pelvis Upper calyx Middle calyx Lower calyx
No. of stones 25 7 5 6
Stone-free rate 21/25 7/7 4/5 5/6
(88%) (100%) (80%) (83.3%)
CIRFs
Table 3 Treatment and retreatment rates for successful cases (stone free and CIRFs). No. of sessions No. of patients
2/25 (8%) e 1/5 (20%) 1/6 (16.6%)
or more sessions as shown in Table 3. Our overall stone-free rate was 86%; 9.3% of patients had CIRFs and were instructed to attend follow up for the possibility of stone re-growth and development of microscopic hematuria and/ or UTI. Two cases (4.7% of all cases) failed to achieve adequate clearance and were deemed failed ESWL requiring further treatment by other methods. Complications were encountered in six (16.5%) of our patients. These were renal colic in three (8.1%), steinstrasse in two (5.4%) and transient fever in one (2.1%). Transient gross hematuria was encountered in 100% of our patients. The patients who had steinstrasse, a failure of ureteric stone clearance, underwent auxillary ureteroscopy for stone extraction.
1 2 3 4 Total: 69
Stone-free rate CIRFs
23 (56.1%) 21 (95.5%) 9 (21.9%) 9 (100%) 8 (19.5%) 2 (40%) 1 (2.5%) 1 (100%) Total: 41 (100%)
1 0 3 0
(0.5%) (0%) (60%) (0%)
Conclusions The results of our study are promising and demonstrate the safety and efficacy of ungated ESWL in pediatric patients. No patient had an episode of cardiac arrhythmia or required conversion to the gated technique. The ungated method did not appear to reduce the efficacy of ESWL. These results encourage the further evaluation and application of this technique.
Conflict of interest/funding
Discussion
None.
ESWL in the adult and pediatric populations is a wellestablished treatment modality for stones. The benefit of the ungated ESWL technique is that it permits a more rapid procedure without pharmacological manipulation, with its potential complications, to slow down the heart. The application of ungated ESWL in adult patients has been associated with cardiac arrhythmias. The underlying mechanism is not fully understood. The purpose of using gated ESWL is synchronization with the electrocardiogram whereby shocks are administered during the refractory period [3,6]. Recent reports demonstrated the safety of ungated ESWL in the adult population with arrhythmias occurring in-between 18% and 21%, but corrected with conversion to the gated technique without any lasting cardiac effects. Even though ungated ESWL is well tolerated, faster, requires less anesthesia and essentially has the same results as gated ESWL, patients have to be closely monitored [3,9]. Previous reports did not address the efficacy and safety of ungated ESWL in the pediatric population with the exception of the work by Rhee and Palmer [7] in 2006. They studied eight children with a median age of 13.5 years who underwent 10 ESWL procedures for renal calculi. The study demonstrated the safety and efficacy of ungated ESWL in pediatric patients, but the limitation was the small number of patients evaluated. Our study, albeit not the first to evaluate the safety and efficacy of ungated ESWL in the pediatric population, is the largest to date of which we are aware. Thirty-seven children underwent 69 ungated ESWL sessions without a single episode of cardiac arrhythmia. The median age (5 years) was less than that reported by Rhee and Palmer [7]. Our success rate with ungated ESWL did not appear to be different from that published for gated ESWL [1,5,10e12].
References [1] D’Addessi A, Bongiovanni L, Sasso F, Gulino G, Falabella R, Bassi P. Extracorporeal shockwave lithotripsy in pediatrics. J Endourol 2008;22:1e12. [2] Segura JW, Preminger GM, Assimos DG, Dretler SP, Kahn RI, Lingeman JEMacaluso JN for the American Urological Association. Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. J Urol 1997; 158:1915e21. [3] Winters JC, Macaluso JN. Ungated Medstone outpatient lithotripsy. J Urol 1995;153:593e5. [4] Ramakrishnan PA, Medhat M, Al-Bulushi YH, Nair P, Al-Kindy A. Extracorporeal shockwave lithotripsy in infants. Can J Urol 2007;14:3684e91. [5] da Cunha Lima JP, Duarte RJ, Cristofani LM, Srougi M. Extracorporeal shock wave lithotripsy in children: results and shortterm complications. Int J Urol 2007;14:684e8. [6] Greenstein A, Kaver I, Lechtman V, Braf Z. Cardiac arrhythmias during nonsynchronized extracorporeal shock wave lithotripsy. J Urol 1995;154:1321e2. [7] Rhee K, Palmer JS. Ungated extracorporeal shock wave lithotripsy in children: an initial series. Urology 2006;67:392e3. [8] Delvecchio F, Preminger G. Management of residual stones. Urol Clin North Am 2000;2:27. [9] Cass AS. The use of ungating with the Medstone lithotriptor. J Urol 1996;156:896e8. [10] Netto NR, Longo JA, Ikonomidis JA, Netto MR. Extracorporeal shock wave lithotripsy in children. J Urol 2002;167:2164e6. [11] Muslumanoglu AY, Tefekli A, Sarilar O, Binbay M, Altunrende F, Ozkuvanci U. Extracorporeal shock wave lithotripsy as first line treatment alternative for urinary tract stones in children: a large scale retrospective analysis. J Urol 2003;170:2405e8. [12] Nijman RJ, Ackaert K, Scholtmeijer RJ, Lock TW, Schroder FH. Long-term results of extracorporeal shock wave lithotripsy in children. J Urol 1989;142:609e11.
Safety of ungated shockwave lithotripsy in pediatric patients Ahmed M. Shouman, Islam A. Ghoneim, Ahmed ElShenoufy, Ali M. Ziada* Division of Pediatric Urology, Aboul-Riche Children’s Hospital, Cairo University, Cairo, Egypt Received 30 July 2008; accepted 21 October 2008 Available online 21 November 2008
KEYWORDS ESWL; Pediatric; Ungated
Abstract Objective: Ungated extracorporeal shockwave lithotripsy (ESWL) in adults is associated with cardiac arrhythmias. We report on the safety and efficacy of this method for treatment of renal calculi in children. Patients and methods: Children under 14 years with radio-opaque renal stones were treated by ungated ESWL. Pre-treatment plain radiographs and intravenous urography and post-treatment ultrasonography and plain films were used to follow up clearance of fragments. All children were monitored for arrhythmias. Results: Thirty-seven children (28 males, nine females) with a median age of 5 years (range 2e14 years) underwent 69 ungated ESWL sessions for renal calculi. Nineteen children had stones located in the left kidney, 17 had stones located in the right kidney and one child had bilateral renal stones. The stone size ranged from 6 to 25 mm (mean 9.9 mm). Shockwave number ranged from 800 to 3650 (mean of 2500 shockwaves per session). All children underwent lithotripsy with a gradual incremental energy increase from 14 to 20 kV. No patient had cardiac arrhythmias or other intra-procedural complications. No patient required conversion to gated ESWL. The overall stone-free rate was 86%. Conclusion: The results suggest that ungated ESWL is safe in children under 14 years. The efficacy was comparable to that of gated ESWL from previously published series. ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction Since its introduction in 1980, ESWL has become the first therapeutic option in most cases of upper-tract urolithiasis, and the technique has been used for pediatric renal stones
* Corresponding author. Tel.: þ20 10 1001136; fax: þ1 619 996 8026. E-mail address: [email protected] (A.M. Ziada).
since the first report of success in 1986. ESWL is a safe and effective method of treatment of urinary calculi in adults. Established guidelines for the use of ESWL in the adult population are based on stone size and technique (i.e. gated); these guidelines have not been as clearly established for children [1e3]. Despite lack of pediatric ESWL guidelines, the safety and efficacy of the method have been documented in the pediatric population, being applied for infants and older children, with a high success rate [4,5]. ESWL can be gated
1477-5131/$34 ª 2008 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2008.10.007
120
A.M. Shouman et al.
(synchronizing shockwaves to the patient’s R-waves on electrocardiogram) or ungated (unsynchronized to the patient’s electrocardiogram). The latter technique, although safe in most patients, has been associated with cardiac arrhythmias in up to 21% of adult patients [6]. The incidence of arrhythmias in children undergoing ungated ESWL has not been established. An initial series of eight patients suggest that ungated ESWL is safe and efficacious in patients younger than 18 years of age [7]. The aim of this work was to study the safety and efficacy of ungated ESWL of renal calculi in children.
Patients and methods Between May 2006 and May 2007, patients younger than 14 years of age undergoing ESWL for renal calculi were evaluated. A total number of 37 children underwent 69 ungated ESWL sessions for treatment of renal calculi. There were 28 males and nine females. Their age ranged from 2 to 14 years with a median age of 5 years. The patients were then categorized according to stone size and location. A total of 43 renal stones were treated ranging in size from 6 to 25 mm with a mean of 9.9 mm. Calculi were on the right side in 17 cases (46%), on the left side in 19 cases (51%), and bilateral in one case (3%). Twelve patients had a previous history of stone disease (32.4%). Six cases had multiple stones per renal unit. Our approach to these cases was to treat the obstructing stone first. All patients met our inclusion criteria which were: an age of 14 years or younger, radio-opaque renal stones up to 25 mm in diameter, favorable anatomy and no contraindication for ESWL (e.g. distal obstruction, PUJ obstruction, stone in a calyceal diverticulum, etc.). Exclusion criteria included radiolucent stones, stones larger than 25 mm in diameter, unfavorable anatomy, uremia, nonfunctioning renal units, severe untreated UTI and bleeding tendency. ESWL was considered successful if patients were rendered stone free as evidenced by lack of any visible fragments on post-ESWL KUB done 3 weeks post-treatment to allow for sufficient clearance. ESWL was also considered successful if residual stones after fragmentation and clearance were clinically insignificant residual fragments (CIRFs), defined as asymptomatic non-infectious and nonobstructive fragments smaller than 4 mm [8]. Unsuccessful ESWL was defined as lack of evidence of disintegration, fragmentation, or clearance after three sessions of ESWL as proven by plain KUB radiographs and abdominal ultrasound. The lithotriptor used was the Dornier electromagnetic Do Li S device with fluoroscopic localization. All procedures Table 1
were performed with the patient under general anesthesia using ketamine 1.5 mg/kg and midazolam 0.05 mg/kg. The medications used had no renal protective effect. The average duration of general anesthesia was 20 min with a range of 15 to 35 minutes. It is to be noted that the bilateral case had bilateral double-J stents inserted ureteroscopically prior to treatment. Treatment started on the left side (with a smaller stone burden) until cleared, followed by complete clearance of the right side. All patients were monitored for arrhythmias in addition to standard cardiac and vital sign monitoring in the ESWL suite and recovery room. No catheters were used for patients undergoing treatment. Infected patients were given perioperative antibiotics for 7 days, with no hospitalization. Data analysis included the total number of shockwaves, power setting, stone clearance (stone-free rate, CIRFs), retreatment rate and complications. Patients were evaluated 1 month post session with renal ultrasonography and plain KUB radiographs. A comparison of pre-treatment imaging (KUB and IVU) and post-treatment imaging (KUB and abdominal ultrasonography) was done to determine clearance of fragments. Stone-free versus CIRFs as well as the need for retreatment was decided 3 weeks post session.
Results Stones less than 1 cm in size showed a very good response to ESWL with excellent fragmentation and clearance on follow-up radiographs (93.8% stone-free rate, 6.2% CIRFs). As the stone size increased, the number of shockwaves and fluoroscopy time per session increased, stone-free rates decreased, and residual fragments requiring retreatment increased (Table 1). The number of shockwaves ranged from 800 to 3650 with an average of 2500 shockwaves per session. All children underwent lithotripsy with a gradual increment in energy from 14 to 20 kV. There was no impact of age, sex, side of the stone on the results of ESWL. The calyceal location of stones in pediatric patients, unlike adults, did not significantly affect stone-free rates. No significant difference was found in stone-free rates among lower calyceal stones and stones in different renal locations (Table 2). Both fluoroscopy time and number of shockwaves showed a proportional increase with increasing size of the stone yet without impact on the success rate. No patient had cardiac arrhythmias or other intra-procedural complications. No patient required conversion to gated ESWL. Of the patients who achieved a successful outcome, 23 (56.1%) required one session while 18 (43.1%) required two
Effect of stone size on the results of ESWL.
Stone size
Total no. of stones
<1 cm 1e2 cm >2 cm Total
16 20 7 43
na Z Not applicable.
Success Stone-free rate
CIRFs
15 17 5 37
1 1 2 4
(93.8%) (85%) (71.4%) (86%)
(6.2%) (5%) (28.6%) (9.3%)
Failure
Mean no. of sessions
0 2 (10%) 0 2 (4.7%)
1.2 1.9 2.8 na
Retreatment rates
3 (12.5%) 9 (35%) 6 (71%) 18
Mean no. of shockwaves
Mean fluoroscopy time (s)
2233 2746 3489 na
160 200 260 na
Ungated shockwave lithotripsy Table 2
121
Effect of stone location on ESWL.
Stone calyceal location Renal pelvis Upper calyx Middle calyx Lower calyx
No. of stones 25 7 5 6
Stone-free rate 21/25 7/7 4/5 5/6
(88%) (100%) (80%) (83.3%)
CIRFs
Table 3 Treatment and retreatment rates for successful cases (stone free and CIRFs). No. of sessions No. of patients
2/25 (8%) e 1/5 (20%) 1/6 (16.6%)
or more sessions as shown in Table 3. Our overall stone-free rate was 86%; 9.3% of patients had CIRFs and were instructed to attend follow up for the possibility of stone re-growth and development of microscopic hematuria and/ or UTI. Two cases (4.7% of all cases) failed to achieve adequate clearance and were deemed failed ESWL requiring further treatment by other methods. Complications were encountered in six (16.5%) of our patients. These were renal colic in three (8.1%), steinstrasse in two (5.4%) and transient fever in one (2.1%). Transient gross hematuria was encountered in 100% of our patients. The patients who had steinstrasse, a failure of ureteric stone clearance, underwent auxillary ureteroscopy for stone extraction.
1 2 3 4 Total: 69
Stone-free rate CIRFs
23 (56.1%) 21 (95.5%) 9 (21.9%) 9 (100%) 8 (19.5%) 2 (40%) 1 (2.5%) 1 (100%) Total: 41 (100%)
1 0 3 0
(0.5%) (0%) (60%) (0%)
Conclusions The results of our study are promising and demonstrate the safety and efficacy of ungated ESWL in pediatric patients. No patient had an episode of cardiac arrhythmia or required conversion to the gated technique. The ungated method did not appear to reduce the efficacy of ESWL. These results encourage the further evaluation and application of this technique.
Conflict of interest/funding
Discussion
None.
ESWL in the adult and pediatric populations is a wellestablished treatment modality for stones. The benefit of the ungated ESWL technique is that it permits a more rapid procedure without pharmacological manipulation, with its potential complications, to slow down the heart. The application of ungated ESWL in adult patients has been associated with cardiac arrhythmias. The underlying mechanism is not fully understood. The purpose of using gated ESWL is synchronization with the electrocardiogram whereby shocks are administered during the refractory period [3,6]. Recent reports demonstrated the safety of ungated ESWL in the adult population with arrhythmias occurring in-between 18% and 21%, but corrected with conversion to the gated technique without any lasting cardiac effects. Even though ungated ESWL is well tolerated, faster, requires less anesthesia and essentially has the same results as gated ESWL, patients have to be closely monitored [3,9]. Previous reports did not address the efficacy and safety of ungated ESWL in the pediatric population with the exception of the work by Rhee and Palmer [7] in 2006. They studied eight children with a median age of 13.5 years who underwent 10 ESWL procedures for renal calculi. The study demonstrated the safety and efficacy of ungated ESWL in pediatric patients, but the limitation was the small number of patients evaluated. Our study, albeit not the first to evaluate the safety and efficacy of ungated ESWL in the pediatric population, is the largest to date of which we are aware. Thirty-seven children underwent 69 ungated ESWL sessions without a single episode of cardiac arrhythmia. The median age (5 years) was less than that reported by Rhee and Palmer [7]. Our success rate with ungated ESWL did not appear to be different from that published for gated ESWL [1,5,10e12].
References [1] D’Addessi A, Bongiovanni L, Sasso F, Gulino G, Falabella R, Bassi P. Extracorporeal shockwave lithotripsy in pediatrics. J Endourol 2008;22:1e12. [2] Segura JW, Preminger GM, Assimos DG, Dretler SP, Kahn RI, Lingeman JEMacaluso JN for the American Urological Association. Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. J Urol 1997; 158:1915e21. [3] Winters JC, Macaluso JN. Ungated Medstone outpatient lithotripsy. J Urol 1995;153:593e5. [4] Ramakrishnan PA, Medhat M, Al-Bulushi YH, Nair P, Al-Kindy A. Extracorporeal shockwave lithotripsy in infants. Can J Urol 2007;14:3684e91. [5] da Cunha Lima JP, Duarte RJ, Cristofani LM, Srougi M. Extracorporeal shock wave lithotripsy in children: results and shortterm complications. Int J Urol 2007;14:684e8. [6] Greenstein A, Kaver I, Lechtman V, Braf Z. Cardiac arrhythmias during nonsynchronized extracorporeal shock wave lithotripsy. J Urol 1995;154:1321e2. [7] Rhee K, Palmer JS. Ungated extracorporeal shock wave lithotripsy in children: an initial series. Urology 2006;67:392e3. [8] Delvecchio F, Preminger G. Management of residual stones. Urol Clin North Am 2000;2:27. [9] Cass AS. The use of ungating with the Medstone lithotriptor. J Urol 1996;156:896e8. [10] Netto NR, Longo JA, Ikonomidis JA, Netto MR. Extracorporeal shock wave lithotripsy in children. J Urol 2002;167:2164e6. [11] Muslumanoglu AY, Tefekli A, Sarilar O, Binbay M, Altunrende F, Ozkuvanci U. Extracorporeal shock wave lithotripsy as first line treatment alternative for urinary tract stones in children: a large scale retrospective analysis. J Urol 2003;170:2405e8. [12] Nijman RJ, Ackaert K, Scholtmeijer RJ, Lock TW, Schroder FH. Long-term results of extracorporeal shock wave lithotripsy in children. J Urol 1989;142:609e11.