Year : 2012 | Volume
: 28 | Issue : 2 | Page : 240--241
Anatomical variations in horseshoe kidney does not affect stone-free rate after percutaneous nephrolithotomy
|How to cite this article:|
Garg M. Anatomical variations in horseshoe kidney does not affect stone-free rate after percutaneous nephrolithotomy.Indian J Urol 2012;28:240-241
|How to cite this URL:|
Garg M. Anatomical variations in horseshoe kidney does not affect stone-free rate after percutaneous nephrolithotomy. Indian J Urol [serial online] 2012 [cited 2021 Dec 3 ];28:240-241
Available from: https://www.indianjurol.com/text.asp?2012/28/2/240/98485
Horseshoe kidney (HSK) is the most common of all renal fusion anomalies, with prevalence of 0.25%  and urolithiasis is the most common complication with a reported incidence of 21-60%.  The purpose of this retrospective, bi-centric study was to identify factors which affect the stone-free rates (SFR) after percutaneous nephrolithotomy (PCNL) in patients with HSK. Forty-seven males and 11 females with HSK underwent PCNL. Percutaneous access was achieved by C-arm fluoroscopy under prone position. Upper and middle calyceal punctures were used in most cases and multiple punctures were used in 13 patients (22.4%). In all cases a 30Fr Amplatz sheath was used and rigid nephroscopy was performed. Pneumatic lithotripsy was used alone in 31% of cases and combined with ultrasonic lithotripsy in 53.4%. In 32.7% of cases, a flexible nephroscope was also used to remove or reposition a stone.
Complete stone clearance was achieved in 38 (out of 58) patients (65.5%) after a single session. Residual stones were located in the upper, middle and lower calyx, and renal pelvis in three (5.1%), three (5.1%), 13 (22.4%) and one patients (1.7%), respectively. The overall SFR was 93.1% at three months with auxiliary treatments. Univariate analysis revealed that SFR did not correlate with the urological team that performed PCNL, patient gender, associated comorbidities, obesity, history of recurrent infections, previous history of stone formation, prior open surgeries, stone site or the degree of hydronephrosis, puncture site (subcostal vs. supracostal), site of punctured calyx (upper/middle/lower) or the number of percutaneous accesses. Use of a flexible nephroscope did not increase SFR. Intra-operative bleeding and the need for intra-operative transfusion did not alter SFR. On univariate analysis, only stone-related parameters affected the SFR. Parameters like complex stone disease, stone burden >5 cm 2 , multiple stones and staghorn stones were associated with an adverse outcome.
Logistic regression analysis revealed that staghorn calculus was the only factor that significantly predicted SFR. Patients with HSK and staghorn calculi were 45 times more likely to have lower SFR after PCNL than those without staghorn calculi. Authors concluded that the presence of a staghorn calculus is the only factor affecting SFR after PCNL and in most of these cases auxiliary treatments are required.
There are various reasons associated with low SFR after PCNL in HSK. First, due to caudal position and malrotation of the kidneys, with the renal pelvis facing anteriorly and the calyces more posteriorly than usual, posterior percutaneous access to an isthmic calyx is more difficult. Therefore, percutaneous access in HSK is optimally obtained through the superior calyx. This provides best access to the pelvis and all laterally directed calyces  and is relatively safe owing to the inferior displacement of the kidneys away from the pleura. The puncture tract is mostly lower, even for superior caliceal puncture, and more medial in contrast to the tract in normal kidneys.  These medially placed tracts are slightly more difficult to dilate, because they traverse through erector spinae and quadrates lumborum muscles.  The tracts are usually longer because of the low-lying kidneys; hence, the length of the standard nephroscope may fall short.  Second, the coexistence of other abnormalities, especially ureteropelvic junction obstruction, may also negatively affect SFR. HSKs are relatively immobile and may hamper the maneuverability of rigid instruments in the kidney. A high SFR is imperative since the spontaneous passage of stone fragments is lower in HSKs than in normal kidneys, possibly due to the high ureteral insertion and impaired urine drainage.
Data of the authors and others  suggest that the most common cause of residual stones is the stones located in the inferior calyx. It is difficult to gain entry into the inferior calyx in patients with HSK. Although the authors have not found any difference in the SFR with the use of a flexible nephroscope it seems to be the only effective way to treat stones in the inferior calyx.
The authors opine that, stone factors are more important in affecting SFR after PCNL in HSK rather than the inherent anatomical abnormality per se and performing PCNL is not more difficult in HSK in comparison to normal kidneys. Also, the rate of success and becoming stone-free in HSK are comparable with the patients without anatomical abnormalities if stone parameters are equivalent.
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