Combined direct visual and imaging guided percutaneous renal access using on shot tract dilation, a case series of novel methods of tract dilatation

Background: Percutaneous nephrolithotomy , (PCNL) is a common urological procedure for dilatation of access during one shot PNL. Methods : Our research is over twenty one cases of one shot visually guided tract dilation PCNL who referred to Sina Hospital between 2017,2018. They all underwent surgery using a specific 28 F dilatators with a customized central lumen which accepts a 4.5 F semi rigid ureteroscope to visually confirm the puncture of target calyx and passing a guide wire. This instrument complex was passed as a one shot dilator after withdrawal of the puncture needle. Results: The mean duration time form insertion of a needle into target calyx until securing a guide – wire inside the collecting system (pelvis, ureter) and the mean time form needle withdrawal to successful dilation and sheath placement were 95 and 252 seconds respectively. There were no intraoperative or postoperative complications a result of this technique. There was no false passage or failed accesses .Total fluoroscopy time for percutaneous access was reduced considerably. Conclusions: Use of modified ureteroscope kit during PNL, for visually confirmed Percutaneous nephrolithotomy , (PCNL) is feasible especially on complex calycealstones or pelvicalyceal Anatomies occasions. guided using shot dilation


Background
Percutaneous nephrilithotomy is the fundamental available endourological nephrolithiasis treatment (1,2).Earning a secure percutaneous access to collecting system through fluoroscopic guidance and tract dilatation are crucial steps toward having a complete successful and safe procedure (3,4).
After successful puncture of the desired calyx, passage of the guide wire beyond the calyx into the pelvis and ureter provides the most secure position to proceed with access dilatation (5,6).Yet many surgeon tend to change their with a more stiff on after the needle is removed to obtain a more rigid rail for introducing subsequent dilators, many have opted to use balloon dilators (7). It is advised to pass a guide wire into the ureter as safety wire or at least have one wire passed beyond the obstructed calyx or stone into the collecting system (in the upper pole calyx for instance) . In order to prevent surgical complications and access failure due to dislodgement of the wire which could 3 happen during several instrument changes for dilation of the tract and aggravated by kidney movement along breathing movements it is suggested to pass a guide wire into the ureter before starting dialation . The large stone bulk occupying the calyx the infundibulum, so it would impossible to pass the wire further down to renal pelvis or ureter which would result in a challenging tract dilation and higher rates of access failure due to wire dislodgement (8,9). In our health center (Sina hospital,Tehran university of medical sciences) we have been using miniaturized PNL in both children and adults using ureteroscope and in few challenging cases we entered the calyx before dilation with the ureteroscope to disintegrate the stone and deploy a wire to proceed further with the dilation to full size. Revisions of this technique led to develop Amplatz dilator which could hold the ureteroscope inside and be used as a single shot dilator for percutaneous access. Feasibility of percutaneous access tract dilation especially in animal models is shown using a visual dilator system (10)     Then this wire and ureteroscope itself was used as the rigid guide and the dilator was advanced gradually and visual confirmation of correct placement of the dilator and the access sheath inside the collecting system was done. In many instances the surgeon passed the whole dilator kit (ureteroscope plus the dilator) in one shot, keeping the ureteroscope aligned over the wire under direct vision and push the dilator forward at the same time with the other hand. All stage could be followed on the fluoroscope before insertion of the nephroscope. The time for access dilation was recorded from withdrawal of the needle sheath up to point that working sheath.
In these case a 30 F access sheath and customized 28 Fr pencil shaped plastic dilator bearing a central lumen were loaded over a semi rigid ureteroscope were used as a visually guided dilator .
The rest of the procedure was then carried out in the standard manner. Data analysis was done using SPSS (v16) software [Statistical procedures for social sciences; Chicago, IIIinois, USA]. Chi-square, Fisher and Pearson regression tests were used and were considered statistically significant at P values less than 0.05.

Results
The mean duration form insertion of needle into target calyx until securing a guide-wire inside the collecting system (pelvis, ureter) was 95 seconds (84-107). Fluoroscopy time (total time required to obtain the access but not the whole operation) was 7-9.

Discussion
Earning a safe and properly placed percutaneous access into the renal collecting system is the basis of having an effective and safe PNL.Tract dilation is typically achieved by several passages of exchangeable flexible dilators of the Amplatz type, metallic telescoping dilators of the Alken type, or a solitary practice inflatable high pressure balloon (8,9), Over time some features of the surgery techniques and the endoscopy's equipments have been progressed to boost the success rate of the PNL procedure. Now, balloon dilation can be the most novel safest one, though it has the drawback of quite high cost and high failure rate in cases of prior surgery or peri-renal fibrosis (11).
Our novel technique improved dilatation to reach a prosperous process to allow safe dilatation and show the significance of those two steps leading to greater satisfaction rate between surgeons. Here we represent a single institution interventional study about the substitute method of under vision 6 dilatation of access during one-shot PNL procedure, particularly in cases of unsuccessful fluoroscopic placements with uncertainty about existence of the guide wire in the system. In fact when the needle is proceeding towards the related target, some radiological sign may confirm its correct insertion and dilation and operative sheath placing are the last steps of the percutaneous tract creation.
A meta-analysis study by Dehong and his colleagues was over the four tact dilation methods for  (17). Semi-rigid ureteroscope was passed percutaneously during the puncture wound between the two guidewires, watching its secure progress using both the endoscopic and the fluoroscopic monitors, till the semi rigid ureteroscope go to the target calyx and the stone can be observed. Then the third guidewire was passed through the operational channel of the semi rigid ureteroscope, maneuvered by the side of the stone, through the infundibulum, into the pelvis and ureter. After that first two guidewires were then detached and usual tract dilatation was then carried out over the guidewire that was positioned into the ureter, following withdrawing the semi rigid ureteroscope. The rest of the process was then done in the usual manner. This method was done over 7 85 patients and in 82 of them the passing of guidewire in to the ureter was successful with mean time of duration equal to 95 seconds (from ureteroscope to ureter entrance) (17).
In our novel method the usage of ureteroscope was only done by as the accessory method for guidewire conducting, so ureteroscopy and dilatation was done simultaneously. Another special safety feature of described visually confirmed tract dilation (VC-PNL) is the ability to visualize the different tissues while the dilator is passing through them and minimizing the risk for invertent injury to adjacent organs such as colon, etc. Consent for publication: As our manuscript does not contain any individual persons' data, so consent for publication is not applicable in this section.
Availability of data and materials: Data will be available on request Figure 1 Lower calyx puncture, guide wired could not be located beyond the infundibulum of the punctured calyx.
12 Figure 2 The new design of access dilation.
13 Figure 3 The progress of new design access dilation is monitored simultaneously through both endoscopic (a) and fluoroscopic monitors (b).