LETTER Reply letter to: Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracorporeal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm : A Meta-analysis and Systematic Review Alkan Cubuk*, Orkunt Özkaptan, Ahmet Şahan We read the article entitled ‘’Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracor-poreal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm : A Meta-analysis and Systematic Review’’ published in Urology Journal(1). The topic is still hot in the urology regarding lower pole kidney stones in 10-20 mm diameters. Although extracorporeal shock wave lithotripsy (ESWL), retrograde intrarenal surgery (RIRS) and percutaneous nephrolitotomy (PCNL) are the available options for the patients with lower pole renal stones 10-20 mm diameter, the decision making among the methods is still controversy. This manuscript is valu- able in this regard. At the present manuscript the authors prepared a very comprehensive meta-analysis of existing evidence to quan- tify and compare the safety and efficacy of PCNL, RIRS and ESWL for lower pole renal stones 10-20mm. They emphasized longer operative time of PCNL and RIRS compared to ESWL. They also reported higher stone free rate, the lower retreatment rate and auxiliary procedure following PCNL with longest hospital stay for PCNL. When it comes to ESWL, the lowest SFR, the higher retreatment rate and auxiliary procedure rate, but a shorter operative time and the shortest hospital stay was reported. The authors indicated stone to skin distance (SSD) as an unfavorable factor for ESWL. This issue is also reported in current literature. SSD was calculated by measuring the distance from the stone to the skin in three angles (0°, 45° and 90°) and the cut-off value for SWL failure was reported in a wide scale from 100 mm to 119 mm(2,3). At the present study the authors presented 10 mm as a predictive value for a criteria of SWL failure. This statement seems to be not correct totally also 10 mm is an impossible value for SSD. In our opinion it was caused by a mis- spelling, and a correction may be informative for the readers. REFERENCES: 1. Junbo L, Yugen L, Guo J, Jing H, Ruichao Y, Tao W. Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracorporeal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm : A Meta-analysis and Systematic Review. Urol J. 2019: 5;16(2):97-106. 2. Pareek G, Hedican SP, Lee FT Jr, Nakada SY. Shock wave lithotripsy success determined by skin-to- stone distance on computed tomography. Urology 2005: 66(5):941–944. 3. Langenauer J, Betschart P, Hechelhammer L,et al. Advanced non-contrasted computed tomography post- processing by CT-Calculometry (CT-CM) outperforms established predictors for the outcome of shock wave lithotripsy. World J Urol. 2018:36(12):2073-2080. Dr. Lütfi Kirdar Training and Research Hospital, Istanbul, Turkey. *Correspondence: Dr. Lütfi Kirdar Training and Research Hospital, Istanbul, Turkey. alkancubuk@hotmail.com. Received December 2020 & Accepted January 2021 Urology Journal/Vol 18 No. 3/ May-June 2021/ pp. 351-352. [DOI: 10.22037/uj.v16i7.6590] Re :“Reply letter to: Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracorporeal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm : A Meta-analysis and Systematic Review” Reply by Author Thank you very much for your careful reading of our research(1) and your valuable comments. It is necessary for us to explain your questions. In our article(1), we indicated stone to skin distance (SSD) as an unfavorable factor for ESWL. As you said this issue was also reported in current literature, and SSD was calculated by measuring the distance from the stone to the skin in three angles (0°, 45° and 90°) and the cut-off value for SWL failure was reported in a wide scale from 100 mm to 119 mm(2,3). So the statement that stone to skin distance (SSD) as an unfa- vorable factor for ESWL is no wrong. What is controversial is the range of this value. In our paper(1), we mentioned “long skin-to-stone distance (> 10mm)”, and the figure of 10mm is controversial. The original manuscript and references are consulted by us. We find that this description is indeed wrong. This correct value should be 10cm, and the mistake was also indeed caused by spelling. We also think that a correction may be informative for the readers, and this description should be corrected to “long skin-to-stone distance (> 10cm)”. Thank you again for your good suggestions. Your suggestions will benefit more readers. I believe that with our efforts, Urology Journal will become better and better. REFERENCES 1. Junbo L, Yugen L, Guo J, Jing H, Ruichao Y, Tao W. Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracorporeal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm : A Meta-analysis and Systematic Review. Urol J. 2019: 5; 16(2):97-106. 2. Pareek G, Hedican SP, Lee FT Jr, Nakada SY. Shock wave lithotripsy success determined by skin-to- stone distance on computed tomography. Urology 2005: 66(5):941–944. 3. Langenauer J, Betschart P, Hechelhammer L,et al. Advanced non-contrasted computed tomography post- processing by CT-Calculometry (CT-CM) outperforms established predictors for the outcome of shock wave lithotripsy. World J Urol. 2018:36(12):2073-2080. 1Department of Urology, Chengdu Second People's Hospital, Chengdu 610000, Sichuan, P.R. China. 2Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong 637000, Sichuan, P.R. China. *Correspondence: Department of Urology, Chengdu Second People's Hospital, Qingyunnan Road 10, Jinjiang District, Chengdu, 610017, Sichuan, China. E-mail: laifei1221@163.com. Received & Accepted Junbo Liu1, Tao Wu2, Fei Lai 1* Letter 352