***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective To compare the one-shot dilation ( OSD ) technique with three other dilation techniques namely telescopic Alken , fascial Amplatz and balloon dilation ( BD ) in terms of safety efficacy and cost effectiveness . Methods During a 3½ year enrollment period , 480 patients who required PCNL surgery were equally r and omized into four groups . All the cases were assessed preoperatively , intraoperatively as well as postoperatively till a period of 3 months . Access time , X-ray exposure time , hemoglobin drop , complications , success rate , etc . , were all assessed and recorded . Results Similar preoperative characteristics were observed in all the four study arms . X-ray exposure time during dilation was significantly reduced for both OSD and BD when compared to sequential Amplatz and telescopic Alken dilation ( Group ALD = 62.1 + 13 , Group AMD = 67.0 + 10 , Group OSD = 36.8 + 7 , Group BD = 38.1 + 6 , p value = 0.01 , post hoc : G4 = G3 < G2 = G1 ) . There was no significant difference between the access time , hemoglobin drop , complication and success rates among the groups . BD was the most expensive dilation method when compared to the other three dilation techniques . Conclusion All the four methods of dilation are equally safe and effective but both OSD and BD are advantageous in terms of lesser fluoroscopy time during dilation . OSD is much cheaper option when compared to BD , and therefore with more experience , it can become the preferable dilation method , especially in the developing countries Abstract Objective : To perform an economical single-step renal dilatation ( RD ) during  percutaneous nephrolithotomy ( PCNL ) , using directly a 30-F Amplatz dilator over the central Alken dilator , in a trial to reduce the operative duration and radiation exposure during RD while avoiding an exchange of dilators that might increase the risk of blood loss . Patients and methods : In a prospect i ve r and omised study including 49 patients divided into two groups , the first had RD before PCNL using the st and ard metallic telescopic dilators ( Alken ) , and the second had RD using the 30-F Amplatz dilator over the central Alken dilator . The operative duration , with X-ray exposure , was calculated . The procedure outcome in terms of complications , stone-free rates and hospital stay was evaluated statistically . Results : The tract was dilated correctly in all cases . The operative duration and X-ray exposure was shorter in patients undergoing single-step RD ( P < 0.05 ) . There were perioperative complications , according to the Clavien grading system , in 17 ( 34 % ) patients but there was no statistically significant difference between the groups . The stone-free rates were comparable in both groups . Conclusion : A single-step RD during PCNL is feasible , with a shorter operative duration and X-ray exposure . The outcomes were comparable with those of a st and ard metallic telescopic RD Objective : To evaluate the safety and feasibility of percutaneous tract dilation by the one-stage method in preschool children . Methods : Between April 2009 and February 2013 , all preschool ( < 6 years ) children who were c and i date s for percutaneous nephrolithotomy were enrolled in this prospect i ve study . Patients were r and omly assigned to dilation by serial metallic dilators ( group I , 31 patients ) or dilation by one-stage Amplatz according to Frattini et al. [ J Endourol 2001;15:919 - 923 ] ( group II , 31 patients ) . The primary endpoint of interest was fluoroscopy time . Secondary endpoints included tract creation and dilation time , success rate and complications . Stone-free status was defined as residuals ≤3 mm . Results : Age , stone size , operation success and operation time were not significantly different between the studied groups . The most common stone composition was calcium oxalate in both groups . The mean ± st and ard deviation of access and fluoroscopy times in groups I and II were 7.3 ± 1.2 min vs. 5.9 ± 1.5 min ( p > 0.05 ) and 70.0 ± 8.9 s vs. 22.0 ± 5.6 s ( p < 0.001 ) , respectively . Postoperative complications included one case of postoperative fever lasting less than 48 h in group I. Conclusions : Percutaneous tract dilation by the one-stage method is safe and effective . Also , it is associated with considerably less radiation exposure in preschool children BACKGROUND AND PURPOSE  Percutaneous nephrolithotomy ( PCNL ) can be done in patients who have previously had open nephrolithotomy . Currently , dilatation of the nephrostomy tract is achieved using an Amplatz renal dilator or telescopic metal dilators in these patients . The aim of this study was to compare the safety and efficacy of the " one-shot " procedure in patients with previous open nephrolithotomy with those of the current telescopic technique . PATIENTS AND METHODS Thirty-one patients with past history of open surgery for kidney stone disease underwent PCNL at our institution from February 2006 to March 2007 . Patients were r and omly divided into two groups according to dilation technique used : group A ( telescopic procedure ) and group B ( one-shot procedure ) . X-ray exposure , blood loss , and complications were evaluated . RESULTS No significant difference in hemoglobin decrease was seen in the two groups . The stone-free and complication rates were the same in the two groups . Fluoroscopy time during the one-shot procedure was significantly shorter than that of the telescopic procedure ( P < 0.000 ) . CONCLUSION Our experience indicated that the one-shot procedure is feasible in patients with previous open nephrolithotomy . It is as safe and effective as the telescopic procedure , with significant reduction in x-ray exposure PURPOSE To assess the feasibility of one-stage acute dilation of the nephrostomy tract with a 30F Amplatz dilator in patients who are c and i date for percutaneous nephrolithotomy ( PCNL ) regardless of whether there is a previous renal scar to make the procedure less time consuming and more cost effective . PATIENTS AND METHODS The outcomes of one-stage tract dilation for PCNL in 100 consecutive patients with and without a history of ipsilateral open stone surgery ( OSS ) , treated by one surgeon , were examined prospect ively . Forty-six patients ( group 1 ) had a history of ipsilateral OSS , and 54 patients ( group 2 ) did not have this history . Demographic data as well as intraoperative information , such as access time and radiation exposure time during access , were recorded . The success of the access technique and its bleeding complications were analyzed between the two groups . RESULTS By applying a " one-stage " technique , the targeted calix could be entered with a success rate of 93 % . There was no difference in the procedural success rate between groups 1 and 2 ( 93.5 % v 92.6 % , respectively ) . All seven failed attempts ( 7 % ; three with previous OSS ) were managed successfully using an Alken dilator to gain access to the proposed calix in the same session . Previous OSS did not impact access time , radiation exposure time during access , postoperative hemoglobin drop , and bleeding complications . There were no visceral and vascular injuries . CONCLUSIONS One-stage tract dilation for PCNL is a safe and effective method in almost every adult patient PURPOSE To compare the effects of one-stage vs gradual dilation techniques during  percutaneous nephrolithotomy ( PCNL )  on postoperative renal scar formation and overall renal function . PATIENTS AND METHODS Of 152 adult patients who underwent surgery during the study period , 48 were r and omized into two groups . In group 1 ( n=19 ) , gradual tract dilation with Alken metallic dilators was used , and in group 2 ( n=29 ) , one-stage tract dilation was used . We compared patient demographics , intraoperative and preoperative parameters , postoperative overall renal function , and renal scar formation on the target renal pole . RESULTS Access time ( P=0.001 ; 95 % confidence interval [ CI ] : 3.19 - 6.30 ) and radiation exposure during access ( P=0.03 ; 95 % CI : 0.03 - 0.66 ) were significantly shorter in group 2 . In group 1 , the decrease in mean technetium-99 m dimercaptosuccinic acid ( 99m-Tc DMSA ) uptake from 44.1±20.1 % to 43.4±19.6 % 4 weeks postoperatively ( -0.7%±0.5 % ; P=0.27 ; 95 % CI : -0.56 - 1.93 ) was not significant . In group 2 , however , there was a significant decrease in post-PCNL 99m-Tc DMSA uptake 2 ( -2.4±0.3 % , from 50.1±13.5 % to 47.7±13.8 % ; P=0.001 ; 95 % CI : 1.13 - 3.66 ) . Four weeks after surgery , new scar formation or progression of the preoperative scar at the site of access were seen in 14 of 29 ( 48.3 % ) patients who were treated with one-stage dilation whereas only 2 of 19 ( 11.0 % ) patients who were treated with gradual dilation developed new scarring at the access site ( P=0.007 ) . CONCLUSION Although the one-stage tract dilation technique reduced radiation exposure and access time , in the short term , it may cause more parenchymal damage than the gradual dilation technique 
    Output:
    
Conclusion OSD is a safe and efficacious tract dilation technique that can reduce the access time , fluoroscopy time and postoperative decrease in haemoglobin level .
No difference was found in the successful dilation rate , stone-free rate , transfusion rate or rate of complications between the OSD and serial dilation groups .
The difference in the length of postoperative hospital stay was uncertain .
OSD may be a better method of tract creation for PCNL