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Complications and Associated Factors of Pediatric Extracorporeal Shock Wave Lithotripsy
Complications and Associated Factors of Pediatric Extracorporeal Shock Wave Lithotripsy Selcuk Yucel,* Yigit Akin, Ahmet Danisman and Erol Guntekin From the Department of Urology, Akdeniz University School of Medicine, Antalya, Turkey
Abbreviations and Acronyms ESWL ⫽ extracorporeal shock wave lithotripsy KUB ⫽ plain x-ray of kidneys, ureters and bladder UTI ⫽ urinary tract infection Submitted for publication August 21, 2011. Supported by the Akdeniz University Scientific Research and Project Unit. * Correspondence: Department of Urology, Akdeniz University School of Medicine, Dumlupinar Bulvari, Kampus 07059, Antalya, Turkey (telephone: 90-242-249-6821; e-mail: syucel@akdeniz. edu.tr).
Purpose: We determined the safety, efficacy and complications of extracorporeal shock wave lithotripsy in managing pediatric urolithiasis and analyzed possible factors affecting the complication rate. Materials and Methods: We retrospectively reviewed 128 patients younger than 16 years who had undergone extracorporeal shock wave lithotripsy with a Lithostar® lithotripter between January 2000 and December 2010. Stone clearance and complications were assessed at postoperative week 1, and months 1 and 3. Success was defined as no radiological evidence of stone, or fragments 4 mm or less. Treatment failure was analyzed to find any correlation with stone size. Complications were assessed with a specific focus on rehospitalizations during postoperative week 1. Results: The overall success rate was 93.5% (115 of 123 patients). Repeat treatment rate was 56.1% (69 patients). Extracorporeal shock wave lithotripsy failed in 8 children, who subsequently required ancillary procedures. Mean stone size in the treatment failure group was 17.03 mm, compared to 13.04 mm in the successfully treated group. A total of 22 patients (17.8%) had complications in postoperative week 1 but only 19 (15.4%, 12 boys and 7 girls) were rehospitalized at that time. Presence of a metabolic risk factor was the only predictive factor for complications. By comparison, we found a lower success rate and higher ancillary procedure rate in the group with complications. Conclusions: Extracorporeal shock wave lithotripsy is effective for pediatric urolithiasis, with a small but substantial morbidity rate. Parents should be informed about possible rehospitalization following extracorporeal shock wave lithotripsy due to complications independent of stone size. Key Words: kidney calculi, lithotripsy, postoperative complications, ureter, urolithiasis
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THE incidence of urinary stone disease in Western countries is 1% to 5%.1 Children may comprise up to 17% of patients presenting with urinary stones in endemic countries.2 Since its introduction for pediatric urinary stone disease in 1986,3 extracorporeal shock wave lithotripsy has become the firstline treatment in children with upper urinary system stones due to its low complication and high success rates.4
Established guidelines for the use of ESWL® in adults are based on stone size, stone type and surgical technique, ie gated or ungated, frequency pulse, and number and power of shock waves. However, these guidelines have not been clearly stated for children. Although ESWL is a relatively noninvasive, effective and safe procedure in children, complications and rehospitalizations cannot be ignored,
0022-5347/12/1875-1812/0 THE JOURNAL OF UROLOGY® © 2012 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
Vol. 187, 1812-1816, May 2012 Printed in U.S.A. DOI:10.1016/j.juro.2011.12.092
AND
RESEARCH, INC.
PEDIATRIC EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
and parents should be informed about the potential risks. Thus, it is imperative to define the factors affecting the complication and rehospitalization rates after ESWL, and the possible association with ancillary procedures for stone clearance. We present our experience with ESWL in children in the last 10 years, with a specific focus on complications and readmission rates with associated prognostic factors such as age, stone size and site, metabolic risk factors, success rate and need for ancillary procedures.
MATERIALS AND METHODS A total of 72 boys and 56 girls 10 months to 16 years old (mean 6.1 years) were treated with low energy ESWL using the Lithostar lithotripter between January 2000 and December 2010. Patients were retrospectively identified using the Akdeniz University Hospital electronic coding index system (MediHasta®) and ESWL unit registry. Of the patients 18 (14%) were younger than 2 years, 48 (38%) were 2 to 5 years, 33 (26%) were 5 to 10 years and 29 (22%) were older than 10 years. All children were evaluated by history, physical examination, urinalysis, urine culture, serum creatinine, blood urea nitrogen, serum electrolyte (sodium, potassium, calcium and phosphate) measurements and coagulation profile. Radiological evaluation included KUB, excretory urography and urinary system ultrasound to define the stone burden and locate the stone. Of the stones 18 were ureteral and 110 were in the kidney (table 1). ESWL was not performed in any patient with a stone larger than 25 mm, abnormal coagulation profile, untreated UTI, presence of nonfunctional renal unit, ureteropelvic junction obstruction or obstructive megaureter, or radiolucent stones. Children with a known UTI received culture specific antibiotics before ESWL and prophylactic antibiotics from the day before to 3 days after ESWL. Sedoanalgesia was given to 108 patients (84%) during ESWL. In 66 children who were younger than 5 years 3 to 4 mg/kg sodium thiopental was administered, and in 42 children older than 5 years 1 to 2 g/kg propofol and 1 to 2 g/kg fentanyl were administered. All sessions were performed as an ungated technique with the patient in the supine position for renal and proximal ureteral stones, and the prone position for middle
Table 1. Stone characteristics
Ureteral location: Lower Middle Upper Kidney location: Renal pelvis Upper calyx Lower calyx Middle calyx
No. Pts
Mean mm Stone Size (range)
6 5 7
8 (4–16) 8.8 (6–12) 9.1 (5–13)
48 18 23 21
16 16 10 14
(7–25) (5–12) (5–11) (4–12)
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and distal ureteral stones, with continuous electrocardiogram monitoring for any possible arrhythmia. The shock wave is started at the lowest power setting (14 kV) and escalated to the maximum (20 kV) until fragmentation is observed on fluoroscopy. The number of shock waves is limited to when fragmentation is observed or a maximum of 1,000 per session for children younger than 5 years and 2,500 per session in children older than 5 years. Pulse frequency was 70 per minute uniformly. ESWL was repeated in cases when residual stone size was larger than 4 mm. The interval between the 2 treatment sessions was at least 7 days to allow passage of fragmented debris before the next session. All children were followed with KUB after ESWL. At postoperative week 1, and months 1 and 3 KUB and urinary system ultrasound were repeated for possible residual fragments. Treatment was considered successful at 1 and 3 months of followup if the residual fragments were 4 mm or less with no infection. All children were enrolled in a pediatric stone disease followup program after successful ESWL to follow residual stones and assess the long-term safety of ESWL. The followup evaluations included stone analysis, serum biochemistry (creatinine, calcium, phosphate, magnesium, uric acid), spot urine pH and cystine, 24-hour urine calcium, creatinine, citrate, oxalate and volume determination, blood pressure measurement, urinalysis, urine culture, and KUB and/or urinary ultrasound. Student t test was used to compare patient and stone characteristics between the successfully treated and failed treatment groups. Chi-square test was used to compare complicated and successful groups in terms of success, stone location, metabolic stone disease and need for ancillary procedures. QuickCalcs software (GraphPad Software, Inc., La Jolla, California) was used for statistical analysis, and statistical significance was considered as p ⬍0.05.
RESULTS A total of 128 children with urinary stones were treated. Five children underwent only 1 session of ESWL, after which they were lost to followup and not analyzed further. Overall success rate was 93.5% (115 of 123 patients) at postoperative month 3. However, overall stone-free rate was 73.9% (91 patients). A total of 32 children (26%) had residual stones after ESWL, of which 24 (19.5%) were 4 mm or smaller and 8 (6.9%) were larger than 4 mm. The success rate for ureteral stones was 75% (12 of 16 stones) and for kidney stones was 96.2% (103 of 107). Mean number of ESWL sessions in the successfully treated group was 1.6 (range 1 to 3). A total of 54 children underwent 1, 64 underwent 2 and 5 underwent 3 sessions of ESWL for a successful result. Overall the repeat treatment rate was 56.1% (69 of 123 patients). Mean number of ESWL sessions for children who were administered anesthesia/sedoanalgesia for complete treatment was 1.26. Number of shock waves per session varied from 760 to
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2,500. Mean number of shock waves for the entire treatment was 2,327, and mean energy setting was 16.6 kV (range 14 to 20). Mean stone size in children treated with ESWL was 13.32 mm (range 4 to 25). Mean stone size was 17.03 mm in the treatment failure group, compared to 13.04 mm in the successfully treated group (p ⬍0.05). Ancillary procedures were required in 8 children (6.5%). Four patients required ureteroscopic lithotripsy, 1 required ureterolithotomy and 3 required percutaneous nephrolithotripsy. A total of 22 patients (17.8%) had complications of ESWL during postoperative week 1 but only 19 (15.4%, 12 boys and 7 girls) were rehospitalized at that time. Of 5 children (22.7%) with steinstrasse complications 3 were identified only at regular office visits with no symptoms. General complaints were nausea/vomiting/intolerance of oral intake (14 children, 63.6%), pain in treated side/renal colic (7, 31.8%), gross hematuria (12, 54.5%) and fever (3, 13.6%). Three children with fever and 16 with inadequate oral intake and/or pain were rehospitalized. Patients were treated with intravenous hydration, antiemetics, analgesics and antibiotics (in case of fever) until they were pain-free and able to tolerate oral intake. Mean ages of children with vs without complications were similar, as were mean stone sizes (table 2). During followup 3 patients with complications required ancillary procedures (percutaneous nephrolithotripsy in 1, ureterolithotomy in 1 and ureteroscopic lithotripsy in 1), compared to 5 in the uncomplicated group (percutaneous nephrolithotripsy in 2 and ureteroscopic lithotripsy in 3). Only 1 steinstrasse complication required ureteroscopic intervention. Double-J® stent was used in 19 children (15.4%) before ESWL due to either large stone burden or high grade of obstruction. ESWL failed in 4 of these patients, with a mean stone size of 21.1 mm. Only 3 children with Double-J stenting were rehospitalized due to pain and/or hematuria.
Table 2. Characteristics of children with vs without ESWL related complications Without With p Value Complications Complications (chi-square) Totals Mean age (yrs) Mean stone size (mm) % Success No. stone location (%): Ureter Kidney No. metabolic risk factor (%) No. ancillary procedure required (%)
104 6.2 13.4 95.2 12 (11) 92 (89) 9 (7.7) 5 (4.06)
19 5.6 12.4 84.2 6 (31) 13 (69) 10 (52.6) 3 (15.7)
⬍0.05 ⬎0.05 ⬍0.05 ⬎0.05 ⬍0.05 ⬍0.05
A total of 83 children (67.5%) were followed for longer than 3 months. The longest followup was 84 months (median 34). Mean serum creatinine level before ESWL was 0.80 mg/dl. At 1 year after ESWL mean serum creatinine was 0.72 mg/dl in 73 children. No child exhibited hypertension, arrhythmia or hemoptysis. Of 83 children 44 underwent metabolic evaluation to identify metabolic urinary stone disease. A total of 19 children exhibited a metabolic abnormality. The most common abnormality was hypocitraturia (13 patients), followed by hypercalciuria (6), cystinuria (4) and hyperoxaluria (2). Of 24 children followed with residual stones 16 had stones 4 mm or smaller. Of these smaller stones 11 cleared at a median of 28 months without any ancillary procedure, 3 remained the same size and 2 became larger with no clinical symptoms. Cystinuria was noted in 4 patients and hypercalciuria in 1. Of the 4 children with cystinuria 3 required percutaneous nephrolithotripsy for stone clearance.
DISCUSSION Upper urinary tract stone disease in children is rare compared to adults but is no less challenging. The refinement of endoscopic management of urinary stone disease has almost allowed it to replace open surgery in children. Several authors have reported high success rates with ureteroscopy (80% to 100%),5–7 or percutaneous management of urinary stones (79% to 88%) in children,8,9 with minimal morbidity. However, endourological management is generally reserved as an ancillary procedure for failed ESWL due to its comparable success rate and higher safety profile. Concerns regarding adverse effects of ESWL on the developing kidneys and surrounding organs have been raised, although no series has demonstrated renal scarring, abnormal blood pressures or permanent organ injuries in the long term. Therefore, ESWL represents an attractive first-line therapy for children with upper urinary tract stone disease. In this study ESWL resulted in a 93.4% success rate, 17.8% complication rate and 15.4% rehospitalization rate during postoperative week 1. In 2 recent reviews on the safety and efficacy of ESWL in a population of 1,866 children D’Addessi et al reported a success rate greater than 70% at month 3 and complication rate of 18% (336 patients).4,10 However, in this large series review rehospitalization was not addressed properly. We strongly believe that informing parents about a greater than 15% readmission rate following ESWL is important. Hence, we aimed to define the factors predicting complications following ESWL. However, stone size, site in the urinary system, age, preoperative infection and preoperative stenting failed to exhibit any
PEDIATRIC EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
statistical significance in predicting a complication. As seen in table 2, the only predictive factor for complications was having a metabolic abnormality (p ⬍0.05). On the other hand, as a clinical end point we found a lower success rate and higher ancillary procedure rate in the group with complications. In our complication group the most common complaint was nausea/vomiting/intolerance to oral intake in 63.6% of patients, whereas there was no mention of such complications in the review by D’Addessi et al.10 When we scrutinize the studies they reviewed, authors with the highest number of patients, such as Muslumanoglu (344),11 Elsobky (142),12 Aksoy (129),13 and Demirkesen (126)14 et al, did not report such symptoms. However, we found those symptoms with or without colic were the most common reason for rehospitalization. It may be speculated that we had discharged those children prematurely. However, our institution uses a home readiness scoring system regarding vital signs, ambulation and mental status, pain and nausea/ vomiting, bleeding and fluid intake after ESWL. Patients who cannot achieve the minimum score are not discharged home. In our series only children younger than 2 years were discharged on postoperative day 2. Assuming that previous authors have underreported nausea/vomiting/intolerance to oral intake symptoms and mixed them with pain/colic (18%),4,10 our rate for colic was still higher (31.8%). Our high rate of pain/colic may be related to the power and number of shock waves used. However, in children a lower kV is desired, and our mean power was 16.6 kV, which is comparable to other studies where a Lithostar was used, although our mean number of shock waves was higher (2,300 vs 1,500).14 In the literature the most frequent complication is hematuria, at 44.6%, compared to 54% in our series. The incidence of fever in our series (13.6%) was comparable to that reported in the literature (12.1%).4,10 However, none of our febrile cases involved UTI, compared to half of the cases in the literature. We believe that prophylactic antibiotic use in high risk cases decreases UTI with no effect on fever. Steinstrasse complications in our series were seen in 22.7% of cases (5 children), with only 2 requiring rehospitalization and 1 requiring surgical stone removal. In most children with fragmented stones in the ureters the stones cleared by themselves. Aydogdu et al compared adult and pediatric ureters in transporting fragments following ESWL and found better stone clearance by pediatric ureters.15 Our observation is similar to theirs, and we conservatively followed children for at least 3 weeks under alpha-blocker treatment. In our study mean stone size was 17.03 mm in the group with failed ESWL, compared to 13.04 mm in
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the successfully treated group (p ⬍0.05). However, we failed to show whether stone size affected the complication rate (13.4 mm vs 12.4 mm, p ⬎0.05). The literature supports the idea that the larger the stone size, the more ESWL failures and more ancillary procedures required in children.16,17 Our comparable complication rates regardless of stone size may be a reflection of patient selection (all stones smaller than 25 mm) and pre-ESWL stenting for high stone burden. Although some authors believe that Double-J stenting increases the complication rate (hematuria, pain, urgency) and ureteral stone clearance, some recommend selective use, as in our patients.11,12,18 We observed 3 complications and 4 failures in 19 stented cases. Nevertheless, it is difficult to draw a conclusion, since mean stone size in the failed stented group was 21 mm. Therefore, in our study the success rate and complication rate according to stent status might not reflect a clinical end point. In our series complications significantly increased the ancillary procedure requirement rate and decreased the success rate (table 2). The only predictive factor for complications was having a metabolic abnormality. Although metabolic abnormalities are noted in at least a third of children presenting with urinary stone disease, they have not been observed to affect the complication or success rate of ESWL, with the exception of cystinuria. In our study 3 of 4 children with cystinuria required percutaneous surgery. We may speculate that children with metabolic risk factors have larger stones, which can increase the complication rate. However, we found no effect of stone size on the complication and rehospitalization rates. Another point in this series is the safety of the ungated ESWL technique in children. There are only 2 studies in the literature describing the ungated technique in children.19,20 We prefer the ungated technique to decrease the duration of the session under anesthesia since shock wave generation is not dependent on the refractory period on the electrocardiogram. The ungated technique involves a temporary arrhythmia risk in 21% of adults.21 We have not observed any arrhythmia in children in whom only the ungated technique is used. In the literature the longest duration of followup after ESWL in children is 4 years, with no long-term complications.22 We did not note any ESWL related long-term abnormality in our study group during a median followup of 34 months. One of the concerns with our success rate could be our definition of success, which is less than 4 mm residual stone. It can be speculated that the term “stone-free” should not be used without complete stone clearance in children, due to the high recurrence rate related to increased likelihood of metabolic risk factors. How-
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PEDIATRIC EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
ever, we observed self-clearance of residual stone fragments smaller than 4 mm in most children (11 of 16). Nevertheless, residual stones increased in size when a metabolic risk factor was present (2 of 16 patients). Therefore, it would be wiser to continue to follow children with a known metabolic risk factor more carefully, particularly in cases of clinically insignificant residual stones.
CONCLUSIONS ESWL in children with upper urinary tract stones smaller than 25 mm seems effective and safe even when an ungated technique is used. Although the rehospitalization rate following ESWL is low (15%), parents should be warned about this possibility and the higher rate of ancillary procedures required, particularly in children with a known metabolic risk factor.
REFERENCES 1. Kroovand RL: Pediatric urolithiasis. Urol Clin North Am 1997; 24: 173.
calculi in pediatric patients. J Pediatr Urol 2011; 7: 248.
2. Tellalog˘lu S and Ander H: Stones in children. Turk J Pediatr 1984; 26: 51.
9. Schuster TK, Smaldone MC, Averch TD et al: Percutaneous nephrolithotomy in children. J Endourol 2010; 23: 1699.
3. Newman DM, Coury T, Lingeman JE et al: Extracorporeal shock wave lithotripsy in children. J Urol 1986; 136: 23. 4. D’Addessi A, Bongiovanni L, Sasso F et al: Extracorporeal shockwave lithotripsy in pediatrics. J Endourol 2008; 22: 1. 5. Yucel S, Akin Y, Kol A et al: Experience on semirigid ureteroscopy and pneumatic lithotripsy in children at a single center. World J Urol 2011; 29: 719. 6. Dogan HS, Onal B, Satar N et al: Factors affecting complication rates of ureteroscopic lithotripsy in children: results of multi-institutional retrospective analysis by pediatric stone disease study group of Turkish Pediatric Urology Society. J Urol 2011; 186: 1035. 7. Thomas JC: How effective is ureteroscopy in the treatment of pediatric stone disease? Urol Res 2010; 38: 333. 8. Kumar R, Anand A, Saxena V et al: Safety and efficacy of PCNL for management of staghorn
15. Aydogdu O, Burgu B, Gucuk A et al: Effectiveness of doxazosin in treatment of distal ureteral stones in children. J Urol 2009; 182: 282. 16. Wadhwa P, Aron M, Seth A et al: Pediatric shockwave lithotripsy: size matters. J Endourol 2007; 21: 141.
10. D’Addessi A, Bongiovanni L, Racioppi M et al: Is extracorporeal shockwave lithotripsy in pediatrics a safe procedure? J Pediatr Surg 2008; 43: 591.
17. Raza A, Turna B, Smith G et al: Pediatric urolithiasis: 15 years of local experience with minimally invasive endourological management of pediatric calculi. J Urol 2005; 174: 682.
11. Muslumanoglu AY, Tefekli A, Sarilar O et al: Extracorporeal shockwave lithotripsy as first line treatment alternative for urinary tract stones in children: a large scale retrospective analysis. J Urol 2003; 170: 2405.
18. Preminger GM, Kettelhut MC, Elkins SL et al: Ureteral stenting during extracorporeal shock wave lithotripsy: help or hindrance? J Urol 1989; 142: 32.
12. Elsobky E, Sheir KZ, Madbouly K et al: Extracorporeal shockwave lithotripsy in children: experience using two second generation lithotripters. BJU Int 2000; 86: 851. 13. Aksoy Y, Ozbey I, Atmaca AF et al: Extracorporeal shockwave lithotripsy in children: experience using a MPL-9000 lithotriptor. World J Urol 2004; 22: 115. 14. Demirkesen O, Tansu N, Yaycioglu O et al: Extracorporeal shockwave lithotripsy in the pediatric population. J Endourol 1999; 13: 147.
19. Rhee K and Palmer JS: Ungated extracorporeal shock wave lithotripsy in children: an initial series. Urology 2006; 67: 392. 20. Shouman AM, Ghoneim IA, El Shenoufy A et al: Safety of ungated shockwave in pediatric patients. J Pediatr Urol 2009; 5: 119. 21. Greenstein A, Kaver I, Lechtman V et al: Cardiac arrhythmias during nonsynchronized extracorporeal shock wave lithotripsy. J Urol 1995; 154: 1321. 22. Brinkman OA, Griehl A, Kuwetrz-Broking E et al: Extracorporeal shock wave lithotripsy in children. Eur Urol 2001; 39: 591.
Abbreviations and Acronyms ESWL ⫽ extracorporeal shock wave lithotripsy KUB ⫽ plain x-ray of kidneys, ureters and bladder UTI ⫽ urinary tract infection Submitted for publication August 21, 2011. Supported by the Akdeniz University Scientific Research and Project Unit. * Correspondence: Department of Urology, Akdeniz University School of Medicine, Dumlupinar Bulvari, Kampus 07059, Antalya, Turkey (telephone: 90-242-249-6821; e-mail: syucel@akdeniz. edu.tr).
Purpose: We determined the safety, efficacy and complications of extracorporeal shock wave lithotripsy in managing pediatric urolithiasis and analyzed possible factors affecting the complication rate. Materials and Methods: We retrospectively reviewed 128 patients younger than 16 years who had undergone extracorporeal shock wave lithotripsy with a Lithostar® lithotripter between January 2000 and December 2010. Stone clearance and complications were assessed at postoperative week 1, and months 1 and 3. Success was defined as no radiological evidence of stone, or fragments 4 mm or less. Treatment failure was analyzed to find any correlation with stone size. Complications were assessed with a specific focus on rehospitalizations during postoperative week 1. Results: The overall success rate was 93.5% (115 of 123 patients). Repeat treatment rate was 56.1% (69 patients). Extracorporeal shock wave lithotripsy failed in 8 children, who subsequently required ancillary procedures. Mean stone size in the treatment failure group was 17.03 mm, compared to 13.04 mm in the successfully treated group. A total of 22 patients (17.8%) had complications in postoperative week 1 but only 19 (15.4%, 12 boys and 7 girls) were rehospitalized at that time. Presence of a metabolic risk factor was the only predictive factor for complications. By comparison, we found a lower success rate and higher ancillary procedure rate in the group with complications. Conclusions: Extracorporeal shock wave lithotripsy is effective for pediatric urolithiasis, with a small but substantial morbidity rate. Parents should be informed about possible rehospitalization following extracorporeal shock wave lithotripsy due to complications independent of stone size. Key Words: kidney calculi, lithotripsy, postoperative complications, ureter, urolithiasis
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THE incidence of urinary stone disease in Western countries is 1% to 5%.1 Children may comprise up to 17% of patients presenting with urinary stones in endemic countries.2 Since its introduction for pediatric urinary stone disease in 1986,3 extracorporeal shock wave lithotripsy has become the firstline treatment in children with upper urinary system stones due to its low complication and high success rates.4
Established guidelines for the use of ESWL® in adults are based on stone size, stone type and surgical technique, ie gated or ungated, frequency pulse, and number and power of shock waves. However, these guidelines have not been clearly stated for children. Although ESWL is a relatively noninvasive, effective and safe procedure in children, complications and rehospitalizations cannot be ignored,
0022-5347/12/1875-1812/0 THE JOURNAL OF UROLOGY® © 2012 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
Vol. 187, 1812-1816, May 2012 Printed in U.S.A. DOI:10.1016/j.juro.2011.12.092
AND
RESEARCH, INC.
PEDIATRIC EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
and parents should be informed about the potential risks. Thus, it is imperative to define the factors affecting the complication and rehospitalization rates after ESWL, and the possible association with ancillary procedures for stone clearance. We present our experience with ESWL in children in the last 10 years, with a specific focus on complications and readmission rates with associated prognostic factors such as age, stone size and site, metabolic risk factors, success rate and need for ancillary procedures.
MATERIALS AND METHODS A total of 72 boys and 56 girls 10 months to 16 years old (mean 6.1 years) were treated with low energy ESWL using the Lithostar lithotripter between January 2000 and December 2010. Patients were retrospectively identified using the Akdeniz University Hospital electronic coding index system (MediHasta®) and ESWL unit registry. Of the patients 18 (14%) were younger than 2 years, 48 (38%) were 2 to 5 years, 33 (26%) were 5 to 10 years and 29 (22%) were older than 10 years. All children were evaluated by history, physical examination, urinalysis, urine culture, serum creatinine, blood urea nitrogen, serum electrolyte (sodium, potassium, calcium and phosphate) measurements and coagulation profile. Radiological evaluation included KUB, excretory urography and urinary system ultrasound to define the stone burden and locate the stone. Of the stones 18 were ureteral and 110 were in the kidney (table 1). ESWL was not performed in any patient with a stone larger than 25 mm, abnormal coagulation profile, untreated UTI, presence of nonfunctional renal unit, ureteropelvic junction obstruction or obstructive megaureter, or radiolucent stones. Children with a known UTI received culture specific antibiotics before ESWL and prophylactic antibiotics from the day before to 3 days after ESWL. Sedoanalgesia was given to 108 patients (84%) during ESWL. In 66 children who were younger than 5 years 3 to 4 mg/kg sodium thiopental was administered, and in 42 children older than 5 years 1 to 2 g/kg propofol and 1 to 2 g/kg fentanyl were administered. All sessions were performed as an ungated technique with the patient in the supine position for renal and proximal ureteral stones, and the prone position for middle
Table 1. Stone characteristics
Ureteral location: Lower Middle Upper Kidney location: Renal pelvis Upper calyx Lower calyx Middle calyx
No. Pts
Mean mm Stone Size (range)
6 5 7
8 (4–16) 8.8 (6–12) 9.1 (5–13)
48 18 23 21
16 16 10 14
(7–25) (5–12) (5–11) (4–12)
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and distal ureteral stones, with continuous electrocardiogram monitoring for any possible arrhythmia. The shock wave is started at the lowest power setting (14 kV) and escalated to the maximum (20 kV) until fragmentation is observed on fluoroscopy. The number of shock waves is limited to when fragmentation is observed or a maximum of 1,000 per session for children younger than 5 years and 2,500 per session in children older than 5 years. Pulse frequency was 70 per minute uniformly. ESWL was repeated in cases when residual stone size was larger than 4 mm. The interval between the 2 treatment sessions was at least 7 days to allow passage of fragmented debris before the next session. All children were followed with KUB after ESWL. At postoperative week 1, and months 1 and 3 KUB and urinary system ultrasound were repeated for possible residual fragments. Treatment was considered successful at 1 and 3 months of followup if the residual fragments were 4 mm or less with no infection. All children were enrolled in a pediatric stone disease followup program after successful ESWL to follow residual stones and assess the long-term safety of ESWL. The followup evaluations included stone analysis, serum biochemistry (creatinine, calcium, phosphate, magnesium, uric acid), spot urine pH and cystine, 24-hour urine calcium, creatinine, citrate, oxalate and volume determination, blood pressure measurement, urinalysis, urine culture, and KUB and/or urinary ultrasound. Student t test was used to compare patient and stone characteristics between the successfully treated and failed treatment groups. Chi-square test was used to compare complicated and successful groups in terms of success, stone location, metabolic stone disease and need for ancillary procedures. QuickCalcs software (GraphPad Software, Inc., La Jolla, California) was used for statistical analysis, and statistical significance was considered as p ⬍0.05.
RESULTS A total of 128 children with urinary stones were treated. Five children underwent only 1 session of ESWL, after which they were lost to followup and not analyzed further. Overall success rate was 93.5% (115 of 123 patients) at postoperative month 3. However, overall stone-free rate was 73.9% (91 patients). A total of 32 children (26%) had residual stones after ESWL, of which 24 (19.5%) were 4 mm or smaller and 8 (6.9%) were larger than 4 mm. The success rate for ureteral stones was 75% (12 of 16 stones) and for kidney stones was 96.2% (103 of 107). Mean number of ESWL sessions in the successfully treated group was 1.6 (range 1 to 3). A total of 54 children underwent 1, 64 underwent 2 and 5 underwent 3 sessions of ESWL for a successful result. Overall the repeat treatment rate was 56.1% (69 of 123 patients). Mean number of ESWL sessions for children who were administered anesthesia/sedoanalgesia for complete treatment was 1.26. Number of shock waves per session varied from 760 to
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2,500. Mean number of shock waves for the entire treatment was 2,327, and mean energy setting was 16.6 kV (range 14 to 20). Mean stone size in children treated with ESWL was 13.32 mm (range 4 to 25). Mean stone size was 17.03 mm in the treatment failure group, compared to 13.04 mm in the successfully treated group (p ⬍0.05). Ancillary procedures were required in 8 children (6.5%). Four patients required ureteroscopic lithotripsy, 1 required ureterolithotomy and 3 required percutaneous nephrolithotripsy. A total of 22 patients (17.8%) had complications of ESWL during postoperative week 1 but only 19 (15.4%, 12 boys and 7 girls) were rehospitalized at that time. Of 5 children (22.7%) with steinstrasse complications 3 were identified only at regular office visits with no symptoms. General complaints were nausea/vomiting/intolerance of oral intake (14 children, 63.6%), pain in treated side/renal colic (7, 31.8%), gross hematuria (12, 54.5%) and fever (3, 13.6%). Three children with fever and 16 with inadequate oral intake and/or pain were rehospitalized. Patients were treated with intravenous hydration, antiemetics, analgesics and antibiotics (in case of fever) until they were pain-free and able to tolerate oral intake. Mean ages of children with vs without complications were similar, as were mean stone sizes (table 2). During followup 3 patients with complications required ancillary procedures (percutaneous nephrolithotripsy in 1, ureterolithotomy in 1 and ureteroscopic lithotripsy in 1), compared to 5 in the uncomplicated group (percutaneous nephrolithotripsy in 2 and ureteroscopic lithotripsy in 3). Only 1 steinstrasse complication required ureteroscopic intervention. Double-J® stent was used in 19 children (15.4%) before ESWL due to either large stone burden or high grade of obstruction. ESWL failed in 4 of these patients, with a mean stone size of 21.1 mm. Only 3 children with Double-J stenting were rehospitalized due to pain and/or hematuria.
Table 2. Characteristics of children with vs without ESWL related complications Without With p Value Complications Complications (chi-square) Totals Mean age (yrs) Mean stone size (mm) % Success No. stone location (%): Ureter Kidney No. metabolic risk factor (%) No. ancillary procedure required (%)
104 6.2 13.4 95.2 12 (11) 92 (89) 9 (7.7) 5 (4.06)
19 5.6 12.4 84.2 6 (31) 13 (69) 10 (52.6) 3 (15.7)
⬍0.05 ⬎0.05 ⬍0.05 ⬎0.05 ⬍0.05 ⬍0.05
A total of 83 children (67.5%) were followed for longer than 3 months. The longest followup was 84 months (median 34). Mean serum creatinine level before ESWL was 0.80 mg/dl. At 1 year after ESWL mean serum creatinine was 0.72 mg/dl in 73 children. No child exhibited hypertension, arrhythmia or hemoptysis. Of 83 children 44 underwent metabolic evaluation to identify metabolic urinary stone disease. A total of 19 children exhibited a metabolic abnormality. The most common abnormality was hypocitraturia (13 patients), followed by hypercalciuria (6), cystinuria (4) and hyperoxaluria (2). Of 24 children followed with residual stones 16 had stones 4 mm or smaller. Of these smaller stones 11 cleared at a median of 28 months without any ancillary procedure, 3 remained the same size and 2 became larger with no clinical symptoms. Cystinuria was noted in 4 patients and hypercalciuria in 1. Of the 4 children with cystinuria 3 required percutaneous nephrolithotripsy for stone clearance.
DISCUSSION Upper urinary tract stone disease in children is rare compared to adults but is no less challenging. The refinement of endoscopic management of urinary stone disease has almost allowed it to replace open surgery in children. Several authors have reported high success rates with ureteroscopy (80% to 100%),5–7 or percutaneous management of urinary stones (79% to 88%) in children,8,9 with minimal morbidity. However, endourological management is generally reserved as an ancillary procedure for failed ESWL due to its comparable success rate and higher safety profile. Concerns regarding adverse effects of ESWL on the developing kidneys and surrounding organs have been raised, although no series has demonstrated renal scarring, abnormal blood pressures or permanent organ injuries in the long term. Therefore, ESWL represents an attractive first-line therapy for children with upper urinary tract stone disease. In this study ESWL resulted in a 93.4% success rate, 17.8% complication rate and 15.4% rehospitalization rate during postoperative week 1. In 2 recent reviews on the safety and efficacy of ESWL in a population of 1,866 children D’Addessi et al reported a success rate greater than 70% at month 3 and complication rate of 18% (336 patients).4,10 However, in this large series review rehospitalization was not addressed properly. We strongly believe that informing parents about a greater than 15% readmission rate following ESWL is important. Hence, we aimed to define the factors predicting complications following ESWL. However, stone size, site in the urinary system, age, preoperative infection and preoperative stenting failed to exhibit any
PEDIATRIC EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
statistical significance in predicting a complication. As seen in table 2, the only predictive factor for complications was having a metabolic abnormality (p ⬍0.05). On the other hand, as a clinical end point we found a lower success rate and higher ancillary procedure rate in the group with complications. In our complication group the most common complaint was nausea/vomiting/intolerance to oral intake in 63.6% of patients, whereas there was no mention of such complications in the review by D’Addessi et al.10 When we scrutinize the studies they reviewed, authors with the highest number of patients, such as Muslumanoglu (344),11 Elsobky (142),12 Aksoy (129),13 and Demirkesen (126)14 et al, did not report such symptoms. However, we found those symptoms with or without colic were the most common reason for rehospitalization. It may be speculated that we had discharged those children prematurely. However, our institution uses a home readiness scoring system regarding vital signs, ambulation and mental status, pain and nausea/ vomiting, bleeding and fluid intake after ESWL. Patients who cannot achieve the minimum score are not discharged home. In our series only children younger than 2 years were discharged on postoperative day 2. Assuming that previous authors have underreported nausea/vomiting/intolerance to oral intake symptoms and mixed them with pain/colic (18%),4,10 our rate for colic was still higher (31.8%). Our high rate of pain/colic may be related to the power and number of shock waves used. However, in children a lower kV is desired, and our mean power was 16.6 kV, which is comparable to other studies where a Lithostar was used, although our mean number of shock waves was higher (2,300 vs 1,500).14 In the literature the most frequent complication is hematuria, at 44.6%, compared to 54% in our series. The incidence of fever in our series (13.6%) was comparable to that reported in the literature (12.1%).4,10 However, none of our febrile cases involved UTI, compared to half of the cases in the literature. We believe that prophylactic antibiotic use in high risk cases decreases UTI with no effect on fever. Steinstrasse complications in our series were seen in 22.7% of cases (5 children), with only 2 requiring rehospitalization and 1 requiring surgical stone removal. In most children with fragmented stones in the ureters the stones cleared by themselves. Aydogdu et al compared adult and pediatric ureters in transporting fragments following ESWL and found better stone clearance by pediatric ureters.15 Our observation is similar to theirs, and we conservatively followed children for at least 3 weeks under alpha-blocker treatment. In our study mean stone size was 17.03 mm in the group with failed ESWL, compared to 13.04 mm in
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the successfully treated group (p ⬍0.05). However, we failed to show whether stone size affected the complication rate (13.4 mm vs 12.4 mm, p ⬎0.05). The literature supports the idea that the larger the stone size, the more ESWL failures and more ancillary procedures required in children.16,17 Our comparable complication rates regardless of stone size may be a reflection of patient selection (all stones smaller than 25 mm) and pre-ESWL stenting for high stone burden. Although some authors believe that Double-J stenting increases the complication rate (hematuria, pain, urgency) and ureteral stone clearance, some recommend selective use, as in our patients.11,12,18 We observed 3 complications and 4 failures in 19 stented cases. Nevertheless, it is difficult to draw a conclusion, since mean stone size in the failed stented group was 21 mm. Therefore, in our study the success rate and complication rate according to stent status might not reflect a clinical end point. In our series complications significantly increased the ancillary procedure requirement rate and decreased the success rate (table 2). The only predictive factor for complications was having a metabolic abnormality. Although metabolic abnormalities are noted in at least a third of children presenting with urinary stone disease, they have not been observed to affect the complication or success rate of ESWL, with the exception of cystinuria. In our study 3 of 4 children with cystinuria required percutaneous surgery. We may speculate that children with metabolic risk factors have larger stones, which can increase the complication rate. However, we found no effect of stone size on the complication and rehospitalization rates. Another point in this series is the safety of the ungated ESWL technique in children. There are only 2 studies in the literature describing the ungated technique in children.19,20 We prefer the ungated technique to decrease the duration of the session under anesthesia since shock wave generation is not dependent on the refractory period on the electrocardiogram. The ungated technique involves a temporary arrhythmia risk in 21% of adults.21 We have not observed any arrhythmia in children in whom only the ungated technique is used. In the literature the longest duration of followup after ESWL in children is 4 years, with no long-term complications.22 We did not note any ESWL related long-term abnormality in our study group during a median followup of 34 months. One of the concerns with our success rate could be our definition of success, which is less than 4 mm residual stone. It can be speculated that the term “stone-free” should not be used without complete stone clearance in children, due to the high recurrence rate related to increased likelihood of metabolic risk factors. How-
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ever, we observed self-clearance of residual stone fragments smaller than 4 mm in most children (11 of 16). Nevertheless, residual stones increased in size when a metabolic risk factor was present (2 of 16 patients). Therefore, it would be wiser to continue to follow children with a known metabolic risk factor more carefully, particularly in cases of clinically insignificant residual stones.
CONCLUSIONS ESWL in children with upper urinary tract stones smaller than 25 mm seems effective and safe even when an ungated technique is used. Although the rehospitalization rate following ESWL is low (15%), parents should be warned about this possibility and the higher rate of ancillary procedures required, particularly in children with a known metabolic risk factor.
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3. Newman DM, Coury T, Lingeman JE et al: Extracorporeal shock wave lithotripsy in children. J Urol 1986; 136: 23. 4. D’Addessi A, Bongiovanni L, Sasso F et al: Extracorporeal shockwave lithotripsy in pediatrics. J Endourol 2008; 22: 1. 5. Yucel S, Akin Y, Kol A et al: Experience on semirigid ureteroscopy and pneumatic lithotripsy in children at a single center. World J Urol 2011; 29: 719. 6. Dogan HS, Onal B, Satar N et al: Factors affecting complication rates of ureteroscopic lithotripsy in children: results of multi-institutional retrospective analysis by pediatric stone disease study group of Turkish Pediatric Urology Society. J Urol 2011; 186: 1035. 7. Thomas JC: How effective is ureteroscopy in the treatment of pediatric stone disease? Urol Res 2010; 38: 333. 8. Kumar R, Anand A, Saxena V et al: Safety and efficacy of PCNL for management of staghorn
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