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Year : 2012  |  Volume : 28  |  Issue : 3  |  Page : 372-373
 

Effect of variation in the anatomy of the pelvi-calyceal system on the success of percutaneous nephrolithotomy-A step ahead


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Date of Web Publication19-Oct-2012

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How to cite this article:
Mandal S. Effect of variation in the anatomy of the pelvi-calyceal system on the success of percutaneous nephrolithotomy-A step ahead. Indian J Urol 2012;28:372-3

How to cite this URL:
Mandal S. Effect of variation in the anatomy of the pelvi-calyceal system on the success of percutaneous nephrolithotomy-A step ahead. Indian J Urol [serial online] 2012 [cited 2019 May 25];28:372-3. Available from: http://www.indianjurol.com/text.asp?2012/28/3/372/102737

Binbay M, Akman T, Ozgor F, SarEi, Erbin A, Kezer C, et al. Does pelvi-calyceal system anatomy affect success of percutaneous nephrolithotomy? Urology. 2011 Oct;78(4):733-7.



   Summary Top


The anatomic properties of the pelvi-calyceal system (PCS) play a role in stone formation and on the success of minimally invasive procedures. [1] The relationship between the PCS anatomy and the success of endourologic procedures, like shock-wave lithotripsy and retrograde intrarenal lithotripsy, has been reported. [2] Though stone size and staghorn type are established independent factors affecting the success of percutaneous nephrolithotomy (PCNL), [3] the PCS anatomy is one of the most neglected aspects of endourologic stone removal and there are no studies till date to report PCS anatomical factors that may affect the success rates of PCNL. The relationship of PCS' anatomic properties like infundibulopelvic angle (IPA), upper-lower calix angle (ULA), infundibular length (IL), infundibular width (IW), PCS surface area (PCS-SA),degree of hydronephrosis and PCS type to the success of PCNL have been evaluated for the first time in this present retrospective study.

The most widely accepted PCS classification system given by Sampaio et al.,[4] classifies PCS into A 1 , A 2 , B 1 and B 2 . IPA is the inner angle formed at the intersection of the ureteropelvic and central axes of the lower pole infundibulum; ULA is the angle between the central axes of the upper and lower pole infundibula; IL is the distance from the most distal point at the bottom of the calyx to which access was performed to the midpoint of the lower lip of the renal pelvis and IW is the widest point along the infundibula in which access was made. Grid technique was used to calculate PCS surface area.

Preoperative intravenous urography (IVU) was done to delineate PCS anatomy while postoperative X-ray KUB and either IVU or CT were done to document stone clearance. Out of the 493 PCNL performed, 389 (78.1%) were successful (Group 1) and 109 (21.9%) were unsuccessful (Group 2) and anatomic factors were compared between both groups. While both groups were similar with respect to age, sex distribution and body mass index, mean stone size was 7.1 cm 2 vs. 9.2 cm 2 in the respective groups.

The PCNL success rate for PCS Type A 1 , A 2 , B 1 , and B 2 was 79.5%, 82.0%, 74.3%, and 80.3%, respectively. Forward stepwise regression analysis showed that PCS-SA was the only independent factor that affected the PCNL success rates. Other anatomical factors were not found to be significantly different among both groups. The best cutoff point for the PCS-SA in predicting the success of PCNL was 20.5 cm 2 and patients with a PCS-SA of <20.5 cm 2 were 1.96 times more likely to undergo successful PCNL.


   Comments Top


A thorough understanding of the PCS anatomy is necessary to perform PCNL although all four PCS types had a similar success in this study. As we get wiser in our understanding of the anatomy of the PCS we realize that a severely dilated and large PCS generally has lower PCNL success rates. Factors responsible for this observation could be because in large PCSs, it is more difficult to reach stones located in other calices through a single access point, stones can escape during fragmentation, making the surgery longer and difficult and fragmented pieces of stone can easily be lost in other calices in large PCSs.

A hypothesis that, in patients with a wider ULA, upper calix would be more easily reached through a lower calix and thus upper calix stones can be cleared through a lower calix access using a rigid nephroscope appears justified. However, no relationship between the ULA and the PCNL success rate was observed. This result could be due to the fact that both simple and complex stones were examined in the present study. Additional studies on the effect of ULA on PCNL success, focusing only on complex or staghorn stones, might show that the ULA is a predictor of PCNL success.

Theoretically speaking, the IW and IL of the punctured calix can be considered as important anatomic factors because they allow one to reach the pelvis or other calyceal cavities. Although these two anatomic factors did not affect the PCNL success rate in this study, these findings might have been influenced by the methods of measurement used. In addition, narrow and long infundibula can be damaged during the dilation phase of PCNL, particularly when standard-size instruments are used. The effect of the IL and IW on bleeding during PCNL should also be investigated further.

The urologist should be aware that patients with a large PCS might have lower PCNL success rates, and these patients should be informed accordingly. The finding of this study that the PCS-SA is a more effective factor than the stone size on PCNL success must be confirmed by additional prospective studies.

 
   References Top

1.Matlaga BR, Assimos DG. Changing indications of open surgery. Urology 2002;59:490-4.  Back to cited text no. 1
[PUBMED]    
2.Geavlete P, Multescu R, Geavlete B. Influence of pyelocaliceal anatomy on the success of flexible ureteroscopic approach. J Endourol 2008;22:2235-9.  Back to cited text no. 2
[PUBMED]    
3.Zhu Z, Wang S, Xi Q,Bai J, Yu X, Liu J. Logistic regression model for predicting stone-free rate after minimally invasive percutaneous nephrolithotomy. Urology2011;78:32-6.  Back to cited text no. 3
    
4.Sampaio FJ, de Lacerda CA. Anatomic classification of the kidney collecting system for endourologic procedures. J Endourol 1998;2:247-51.  Back to cited text no. 4
    




 

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