Year : 2003 | Volume
: 20 | Issue : 1 | Page : 14--17
Single step access into the pelvicalyceal system using the webb target dilator for PCNL and comparison with sequential dilatation technique
Apul Goel, Monish Aron, Rajiv Goel, NP Gupta, AK Hemal, PN Dogra, Amlesh Seth
Department of Urology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
Department of Urology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
Objectives: To evaluate the effectiveness and safety of the single step dilatation of the pelvicalyceal system using the Webb target dilator.
Methods: Thirty consecutive patients who underwent PCNL using the Webb dilator were compared with 30 patients in whom sequential dilatation was done. The two groups were similar as regards age, stone location and degree of hydronephrosis.
Results: The Webb dilator was associated with a lesser time for tract dilatation as compared to the sequential dilatation group. There were no significant complication in either group. There was a higher incidence of failure of adequate access to pelvicalyceal system with the Webb dilator group if the pelvicalyceal system was not dilated.
Conclusions: The Webb target dilator is a safe, rapid and effective method of tract dilatation during PCNL and is associated with significantly shorter time in tract dilatation as compared to the sequential dilatation group. However it is not suitable for non-dilated pelvicalyceal systems.
|How to cite this article:|
Goel A, Aron M, Goel R, Gupta N P, Hemal A K, Dogra P N, Seth A. Single step access into the pelvicalyceal system using the webb target dilator for PCNL and comparison with sequential dilatation technique.Indian J Urol 2003;20:14-17
|How to cite this URL:|
Goel A, Aron M, Goel R, Gupta N P, Hemal A K, Dogra P N, Seth A. Single step access into the pelvicalyceal system using the webb target dilator for PCNL and comparison with sequential dilatation technique. Indian J Urol [serial online] 2003 [cited 2022 Jul 1 ];20:14-17
Available from: https://www.indianjurol.com/text.asp?2003/20/1/14/37117
Percutaneous nephrolithotomy (PCNL) has become the standard of care for most renal calculi not amenable to shockwave lithotripsy (SWL).  PCNL involves accessing the pelvicalyceal system (PCS) through a l cm incision, usually employing sequential dilators over a guide wire. Efforts have been made to simplify this process of entry into the PCS, by means of single step dilators like the balloon dilator and the Webb target dilator [Figure 1]. This study was designed to study the safety and efficacy of the Webb dilator in providing a one-step entry into the PCS and the results compared with the standard technique.
Patients and Methods
Thirty consecutive patients who underwent PCNL using the Webb target dilator at our center between July and December 2001 were included in the study. This group was compared with 30 controls in which standard sequential teflon dilators were used and performed during the same period. The inclusion criteria were age, 16-65 years, and stone size, 2 to 6 cm. No attempt was made at matching the two groups. No patient was excluded on the basis of stone or PCS configuration, patient or surgeon preference and comorbidity. All the patients had normal renal parameters. An intravenous urogram was performed in all the patients and the hydronephrosis defined as severe when the calyces were ballooned with reduction in cortical thickness to less than 1 cm. Hydronephrosis was deemed moderate when the calyces were clubbed but cortical thickness was greater than 1 cm. Hydronephrosis was considered mild when there was only blunting of the fornices. The stone size was measured as the sum of the largest dimensions of the stones present in an individual case. Parameters noted were time taken from initial puncture to placement of Amplatz sheath in the PCS, success rate of Amplatz placement and complications of the dilatation. Success was defined as secure placement of distal end of the Amplatz sheath inside the PCS as seen on the first insertion of the nephroscope. Data was collected and analyzed statistically by an independent observer and the statistical analysis performed using the student `t' test and chi square test.
The technique included a retrograde placement of ureteral catheter in the supine position under general anesthesia, following which the patient was turned prone. A fluoroscopy guided puncture was made into the desired calyx and a guide wire stabilized inside the PCS or down the ureter. An 8-10 mm incision was made adjacent to and including the puncture site down to the lumbodorsal fascia. The Webb dilator (26F) was threaded onto the wire and introduced into the PCS in a coaxial manner using gentle rotating movements. A 26/30F Amplatz sheath was introduced over the dilator into the PCS and nephroscopy commenced using either a 21F or 26F nephroscope. If the sheath was just short of the system the wire was followed with the nephroscope to gain entry. If a counterperforation was encountered, the sheath was withdrawn and repositioned under vision. In the control group tract dilatation was done using the teflon sequential dilators and the tract dilated up to 30F and an 30/34 Amplatz inserted. Calculi were fragmented with lithoclast and removed. A 20F nephrostomy tube was placed at the end of the procedure.
Patient characteristics and results are shown in [Table 1]. The time taken to perform the dilatation was significantly shorter in the Webb dilator group. The success rate of secure sheath placement was less in the Webb dilator group although the difference was not statistically significant. In the sequential dilator group the Amplatz sheath was short of the system in only one patient while in the Webb dilator group, the Amplatz sheath was short of the system in 5 cases. All these patients had none to mild hydronephrosis with stone filling the entire calyx chosen for entry. No patient had undue hemorrhage or post-operative perirenal hematoma. Counter perforation was encountered in 1 case in the sequential dilator group and in 2 cases in the Webb dilator group. A single Webb dilator was used in all the patients in this series and it could be used in another 15 patients before it became unusable due to fraying of the tip.
Various methods have been described for gaining access into the pelvicalyceal system. After performing an initial puncture into the desired calyx a guide wire is secured into the PCS or into the ureter. This tract is then dilated to usually 24 to 30F that can be performed either as a single step dilatation or multi-increment dilatation. The multi-increment dilatation can be done using multiple sequential teflon dilators  or metal telescoping dilators. , Single step dilatation can be performed by either the balloon dilator  or the Webb target dilator. 
Many studies have been performed to study the damage caused by tract dilatation during PCNL. Webb and coworkers evaluated the renal damage experimentally in dogs in which they studied the effect of multi-increment dilatation.  Nephrostomy tracts were established and dilated to 22, 24 and 30 F using graduated dilators. The kidneys were then harvested at 48 hours and at 6 weeks. There was no significant loss of canine renal parenchyma and at 6 weeks, all nephrostomy tracts had healed to a fine scar despite dilating the tract to an equivalent human size of 35 to 50 F. Clayman et al evaluated the amount of renal damage following nephrostomy tract dilatation in pigs.  Dilatation was done either by semi-rigid 24 F fascia] dilating system or 36 F balloon dilating system. The amount of renal damages averaged 0.15% of the measured renal cortex. There was no statistically significant difference between the two modalities of dilatation, and all nephrostomy tracts healed in 6 weeks to fine scar. Travis et al performed an experimental study on dogs to evaluate the amount of renal damage caused by the Webb target dilator.  They found it to be safe technique with minimal hemorrhage or parenchymal damage and healing at 6 weeks by a fine linear scar and were as safe as conventional techniques.
Single-step entry into the PCS has obvious appeal to all endourologists performing PCNL. However, the balloon device available for this purpose is expensive and being disposable is an obvious drawback in developing countries. We report on our initial experience with the Webb target dilator (Cook Urological® ), which is a teflon onestep dilator that is introduced directly over the guide wire. The advantage of this dilator is the rapidity of entry that is achieved. In the present series this difference was statistically significant as the time taken for tract dilatation was less in the Webb target dilator group. Another benefit is that the constant tamponade reduces the blood loss that is usually observed during the exchanges that are required with semi-rigid, graduated dilators. Moreover, because of the rapidity of dilatation there is less radiation exposure to the surgeon and the patient. However, it has limitations when there is no hydronephrosis or when the stone completely packs the chosen calyx, the reason being that although the tip of the dilator enters the PCS the shaft of the dilator remains in the parenchyma. The length of the taper of the Webb dilator is 15-mm; therefore, at the end of dilation a rim of parenchyma may remain between the sheath and the stone. We did encounter this problem in five cases of Webb target dilator, where the sheath was just short of the system. In all these cases (as also in the one patient in the sequential dilator group) we entered the collecting system by following the guidewire into the system under nephroscopic vision and then advancing the sheath over the nephroscope till the tip of the sheath came to lie in the desired calyx. We feel that Webb target dilator is not suitable for non-dilated PCS. Another limitation is that the dilator is available in a maximum size of 26F. Thus Amplatz sheaths of larger internal diameters cannot be inserted directly.
The Webb target dilator is a safe, single-increment dilatation method to access the PCS during PCNL. The time required to dilate the tract is much less with the Webb dilator as compared to the conventional sequential exchange dilator method. It has limitations when there is no hydronephrosis or when the stone completely packs the chosen calyx, although, the difference in success rates is not significantly less than the sequential group. Another limitation is that the Webb dilator is available in a maximum size of 26F. No significant complications were noted with this method of dilatation.
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