the historic open surgery for stones has been replaced by less - invasive modalities , particularly extracorporeal shockwave lithotripsy ( eswl ) and percutaneous nephrolitotomy ( pcnl ) being advocated as primary treatment , each alone or in combination . for adult nephrolithiasis , retrograde intrarenal surgery ( rirs ) is a known option to treat upper tract calculi with excellent success . in children , rirs emerged over the last couple of decades and is now an established and accepted modality for kidney stone management . the european ( eua ) and american urological associations guidelines for pediatric renal stones still advocate eswl as the first - choice treatment modality , followed by pcnl for larger or complex calculi . nonetheless , the miniaturization of endoscopes , fiber - optics technology , availability of holmium : yag laser and other ancillary instruments have rendered rirs an attractive modality for pediatric patients . with ongoing accumulation of experience in pediatric rirs , we sought to address its current status focusing on its indications , outcomes and success in the management of nephrolithiasis in children . we conducted a comprehensive pubmed / medline search of the available literature on rirs between the years 1988 and 2009 . prior to 1988 , pediatric ureteroscopy was not described and articles prior to this period were excluded . we focused on patient populations , stone characteristics , including size and location , and outcomes , including stone burden clearance and complications , in contemporary case series addressing pediatric patients with renal stones . over the last half decade , less than a dozen case series are published reporting on their experience in utilizing rirs for the management of renal stones in children [ table 1 ] . many of those case series[811 ] had small study populations and included the outcome of ureteral calculi , being the major stone location managed , to the overall analysis . reporting on a heterogeneous stone location skewed and increased the success rates to a misleading higher rate ranging from 88 to 100% . had one of the largest case series of 100 patients , one - third of who had renal stones . a success rate of 91% is reported , noting that the average size of the stones was only 8 mm . the outcome for renal stones was not reported separately and more than 20 patients underwent ureteroscopy as a staged or a secondary procedure , making it difficult to interpret the outcome of rirs as a single modality . cannon et al . noted a 76% success rate in a series of 21 patients , all having lower pole stones averaging 1.2 cm in size . similar success was noted in a study from our institution , where dave et al . polar calculi had a 100% success , but results should be cautiously interpreted as only four patients were treated ( two upper pole and two lower pole ) , all requiring multiple sessions ( 2 - 3 times ) . of note , seven patients had staghorn calculi , with a discouraging success rate of 14% . the childrens hospital of philadelphia recently reported the largest case series utilizing flexible pediatric ureteroscopy with rirs used to manage 101 renal stones ( 87 lower polar ) . for an arbitrary cut - off of 10 mm , this study shows a success rate of 100% for sub - centimetric calculi , yet an impressive 97% success for calculi larger than 1 cm . however , it is noteworthy that access was not possible in the first surgery for 59% of the patients , raising concerns for additional anesthesia for more than half of their patients . in another recent publication , tanaka et al . reported their 5-year experience on pediatric rirs , noting a 50% stone - free rate on initial post - operative follow - up and 58% on extended follow - up . peculiar to this study is its assessment of the influence of pre - operative factors on initial stone - free status and the need for extra procedures . interestingly , initial stone - free status depended on pre - operative stone size ( p = 0.005 ) but not on stone location . the younger patient age ( p = 0.04 ) and larger pre - operative stone size ( p = 0.002 ) influenced the need for extra procedures that were required in more than half of the stones 6 mm but in no stone < 6 mm . contemporary results of rirs for pediatric renal calculi technical aspects associated with rirs include the need of dilatation and stenting . intuitively , dilatation of the ureter would be needed when larger rigid ureteroscopes are used . in fact , bassiri et al . performed 66 rigid ureteroscopies using 11.5 , 9 , 8.5 or 8 fr ureteroscopes on 26 , 14 , 5 and 21 patients ( mean age 9 years , range 2 - 15 years ) , respectively ; ureteral dilatation was necessary in 23 , 0 , 0 and 2 cases , respectively . did not require dilatation using wolfe 4.5 fr or 6.5 fr tapered semi - rigid ureterescope alongside a guide wire to access the upper tracts for stones . with the advent of flexible ureteroscopes , rendered as fine as 4.5 fr , coupled with ureteral access sheaths , dilatation of the ureter becomes virtually pointless . indeed , in the philadelphia flexible ureteroscopy case series , no ureter was actively dilated . some investigators prophylactically stented all their patients based on perceived complexity or difficulty of case , with no clear indicators ; dangler strings , to obviate the need of further general anesthesia , were again used based on unclear surgeon discretion . stented six of 29 children ( 21% ) : two had infection associated with either autonomic dysreflexia or stone impaction , two for extravasation or perforation , one for edema and one for subsequent eswl . this is particularly crucial in the pediatric population that is by default considered high risk for complications and for recurrence . the importance of post - treatment stone - free status in children was demonstrated by afshar et al . , who showed that 69% of the children with residual fragments 5 mm up to 48 months after eswl had symptomatic episodes or increase in stone size . this feature of pediatric stone disease should be factored in the choice of treatment modality . indeed , ureteroscopy in children lagged behind its use in adults owing to the initial unavailability of small instruments , coupled by the plethora in eswl in the 1980s . however , eswl was not the panacea in renal stone management , despite a cumulative success rate of 60 - 99% . the results of eswl are worse in stone burden of 2 cm , lower pole or impacted ureteropelvic junction stones and in dense stones composed of calcium oxalate monohydrate or cystine . the main drawback of eswl is , depending on stone burden , that up to 75% of the patients would require multiple sessions . in children , that would translate into additional general anesthesia sessions and further radiation exposure , which opposes the concept of minimizing interventions and fluoroscopy in children to as low as reasonably achievable . recent concern arises on the possible long - term risks of hypertension and diabetes with eswl . the susceptibility of pediatric kidneys in this regard is still unexplored . it remains to say that eswl is still not food and drug administration approved in children . on the other hand , pcnl has a role in larger stone burden / staghorn calculi , acute obstruction or infection and after failed eswl . despite a success rate of 85 - 98% and  mini - perc  modification , pcnl remains relatively invasive , which is restrictive in infants and younger children as well as when further procedures for recurrent stones are required.[2527 ] with the realization of the limitations of eswl and pcnl and the progressive technology in miniaturization of semi - rigid ureteroscopes , ritchey et al . adopted retrograde endoscopy for pediatric distal ureteral stones in 1988 , with high success approaching 100% . further refinement of flexible scopes , as fine as 4.5 fr , with durability and improved optics , has expanded the use of retrograde endoscopic surgery to target more proximal stones as first - line modality . holmium : yag laser offered an efficient energy source for now possible single - session treatments and 270 deflecting tips offered access to lower calyceal stones . as rirs was getting established in clinical practice , concerns were raised regarding its safety and efficacy as well as its potential complications . in theory , manipulation of the delicate ureteral orifices and ureters in children could lead to ischemic insult as well as dilation and decompensation of the ureterovesical junction , leading to vesicoureteral reflux , ureteral strictures , perforation or avulsion . reviewed 221 ureteroscopies in children and found only two patients developing strictures and eight having low - grade vesicoureteral reflux . this low complication rate was not correlated with the size of the scope used , duration of the procedure or the length of follow - up . after single treatment , 16 of 17 ( 94% ) patients were stone free after ureteroscopy versus 6 of 14 ( 43% ) patients being stone free after eswl . pearle et al . compared rirs to eswl in a prospective randomized trial in their efficacy on lower pole stones up to 1 cm . on follow - up imaging , 35% of eswl treated versus 50% of rirs treated were stone free ( p - value not significant ) . retrospectively compared a 15-year experience ( 1988 - 2003 ) with different stone management modalities . they concluded that for renal stones < 20 mm , eswl was the most effective primary treatment modality . for renal stones 20 mm or staghorn stones , pcnl was the preferred primary treatment with lower rates of ancillary procedure and re - treatments . holmium laser ureteroscopy and rirs had high stone - free rates and low complication rates , but superiority was demonstrated for ureteral stones only [ table 2 ] . : comparative outcomes for different treatment modalities finally , it was shown that ureteroscopy is more cost - effective than eswl . retrospectively compared the cumulative cost of treatment for proximal stones of 111 patients undergoing eswl ( 73 with stones < 1 cm ) versus 109 patients undergoing ureteroscopy ( 81 with stones < 1 cm ) over 1997 - 2001 . in the ureteroscopy group , 91% were successfully treated with one intervention versus 55% of the eswl group ( p < 0.0001 ) . with ureteroscopy failure , the ureteroscopy group required fewer days to be stone free ( 8 versus 25.5 days , p < 0.0001 ) . ureteroscopy had significantly lower charges for the initial procedure ( $ 7,575 versus $ 9,507 , p < 0.0001 ) and lower total charges ( $ 9,378 versus $ 15,583 , p < 0.0001 ) . although this applies for ureteral stones , no similar studies were conducted for renal stones . no doubt , there is an increasing trend in the adoption of rirs as both a first line and a single modality in the management of renal stones in children . this has been facilitated by both the rapidly evolving technology and the particular drawbacks that are intrinsically associated with eswl and pcnl . however , particular clinical scenarios , for example , anatomic anomalies , concomitant renal and ureteral stones , and decreased fragment clearance after eswl , stone burden in size and multiplicity or dense stones ( cystine ) not favorable for eswl , need to be factored into the decision - making process to which treatment modality / combination is preferable . the initial concerns of increased risks and complications associated with ureteroscopic manipulation of the delicate ureteral orifices and ureters of children do not seem to be substantiated in the literature . there remains , however , a limited and a non - uniform reporting in the literature of the outcome of rirs in children , making the surgeon 's experience of principal importance in counseling and offering treatment to children with renal stones . in addition , access to technology and resources in different parts of the world is inconsistent . until prospective randomized trials comparing different treatment options are available , the ideal management of pediatric renal stones remains individualized rather than standardized .
purposeto review the current status of retrograde intrarenal surgery ( rirs ) for renal stones in children focusing on its indications , outcomes and success in the management of nephrolithiasis.materials and methodsbetween 1988 and 2009 , a comprehensive pubmed / medline literature review on rirs was conducted.resultsthe available literature is limited and heterogeneous , skewed by favorable results on ureteral stone outcomes . 
 however , recent case series report outcomes comparable to time - honored modalities : percutaneous nephrolithotomy and shock wave lithotripsy . concerns about urinary tract damage are not substantiated by the yet available intermediate - term follow-up.conclusionsrirs seems to be an effective modality in pediatric nephrolithiasis management . 
 however , long - term outcomes and comparative prospective randomized studies are awaited .