Original Paper
Urologia Internationalis
Received: August 23, 2013 Accepted after revision: October 22, 2013 Published online: January 29, 2014
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
Skin-to-Stone Distance Has No Impact on Outcomes of Percutaneous Nephrolithotomy Umut Gonulalan a Murat Akand c Gokcen Coban b Tufan Cicek a Murat Kosan a Serdar Goktas c Hakan Ozkardes d Departments of a Urology and b Radiology, Başkent University, and c Department of Urology, Selçuk University, Konya; d Department of Urology, Başkent University, Ankara, Turkey
Key Words Obesity · Percutaneous nephrolithotomy · Skin-to-stone distance · Success
Abstract Objective: Skin-to-stone distance (SSD) is a stronger factor than body mass index in predicting the success of shock wave lithotripsy. We aimed to evaluate the impact of SSD on outcomes of percutaneous nephrolithotomy (PCNL). Materials and Methods: The medical records of 1,280 patients who had undergone PCNL between April 2007 and February 2012 were evaluated retrospectively. 192 patients who had had preoperative non-contrasted computed tomography and single renal access were included the study. According to this median SSD value, patients were divided into two groups: group 1 (SSD ≤94 mm) (n = 92) and group 2 (SSD >94 mm) (n = 90). The groups were compared according to operative and postoperative parameters. Results: We found no significant differences between the two groups with regard to stone-free rate, operation time, fluoroscopy time, hospitalization time, visual analog score of pain, stone burden, transfusion rates and complication rates. On the other hand, the mean body mass index of group 1 was significantly lower than that of group 2 (p < 0.05). Conclusions: In this
© 2014 S. Karger AG, Basel 0042–1138/14/0924–0444$39.50/0 E-Mail [email protected] www.karger.com/uin
retrospective review of patients undergoing PCNL, we found that SSD has no impact on operative and postoperative outcomes. These results were in accordance with the safety of PCNL in obese patients. © 2014 S. Karger AG, Basel
Introduction
Percutaneous nephrolithotomy (PCNL) has been used for stones >2 cm, complicated or staghorn stones in the upper urinary tract since it was first described in 1976 by Fernström and Johansson [1–3]. In the treatment of renal stones in obese patients, extracorporeal shock wave lithotripsy (ESWL) is being used restrictedly due to both weight limitation of the device and larger skin-to-stone distance (SSD), and PCNL is preferred more commonly [4]. Studies evaluating the effect of obesity on the outcomes and complications of PCNL with high caseloads have reported that obesity does not affect the safety of this technique but lowers the stone-free rates [5, 6]. SSD increases due to localization of the stone, increase in subcutaneous and visceral adipose tissue, and thickness of the renal parenchyma. The association between renal parenchymal thickness and the efficacy and safety Umut Gonulalan, MD Başkent University School of Medicine Konya Research and Training Hospital Saray Street, No: 1 Selçuklu, Konya (Turkey) E-Mail drugonulalan @ yahoo.com
of PCNL has been studied by Tepeler et al. [7]. Studies evaluating the effect of SSD on the success of ESWL have demonstrated that increased SSD lowers the stone-free rates after ESWL [8–10]. In those studies, SSD was established as a stronger factor than body mass index (BMI) in predicting the success of ESWL [9, 10]. In this study, we aimed to investigate the effect of SSD on the success and safety of PCNL. Materials and Methods Study Group The files of 1,280 patients who had undergone PCNL due to upper urinary tract stone disease between April 2007 and February 2012 in Başkent University, Konya Practice and Research Center, and Selçuk University, Medical School, Urology Department, were evaluated retrospectively. Exclusion criteria for this study were age 94 mm). Evaluated Data Blood biochemical parameters, complete blood count, demographic properties, operation properties and postoperative complications of the patients were recorded from medical recordings retrospectively. Stone size and area were evaluated with NCCT, and the calculation of stone area was done with the following formula: stone area = length × width × π × 0.25 [11]. Postoperative complications classified according to the modified Clavien classification (MCC) were compared [12]. Surgical Technique First, patients underwent cystoscopy for retrograde catheterization in the lithotomy position under general or spinal anesthesia, and a 5F or 6F ureteral catheter was placed. Afterwards patients were taken into the prone position. The targeted calyx was entered with an 18-gauge needle under bi-planar fluoroscopy, and the tract was dilated to 30F by either balloon or Amplatz dilatators over the guide wire. A standard PCNL procedure was performed, with the lithotripsy done by pneumatic lithotripter, and the stones taken with the grasping forceps. At the end of the operation, the success was evaluated with the help of fluoroscopy. Stones 2 cm, complicated or staghorn stones in the upper urinary tract [1–3, 13]. In the treatment of renal stones in obese patients, PCNL is preferred to ESWL due to long SSD [4]. It has been found that PCNL is safe in obese patients, but with a lower stone-free rate [5, 6]. SSD increases due to localization of the stone, increase in 446
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
subcutaneous and visceral adipose tissue, and thickness of the renal parenchyma. An increase in renal parenchymal thickness does not have an impact on the efficiency and safety of PCNL [7]. In this study, the effect of SSD on the success and safety of PCNL was studied. Although BMI is a widely used index for obesity, various research has shown that visceral adipose tissue is a better deterministic factor for risk than BMI, especially Gonulalan/Akand/Coban/Cicek/Kosan/ Goktas/Ozkardes
in endoscopic operations [14, 15]. In the same way, it has been identified as a stronger factor than BMI in determining the success of ESWL [9, 10]. Also in our study, the BMIs of patients in group 1 (with a shorter SSD) were statistically significantly lower than those of patients in group 2. This result gave rise to the thought that SSD values were increased due to increased visceral and subcutaneous adipose tissue in patients with a higher BMI. BMI can be a determinant factor for surgical outcomes. In their study of 3,709 patients who underwent PCNL and were classified according to their BMI, Fuller et al. [5] reported that the stone-free rate declined from 77.5 to 65.6% as the obesity of the patients increased. On the other hand, El-Assmy et al. [6] stated that obesity did not affect the stone-free rate, which differed between 83.7 and 86.7%. It was supported by other studies with smaller patient numbers [16, 17] that obesity does not have an influence on stone-free rates after PCNL. In another study assessing the effects of renal parenchymal thickness on PCNL outcomes, no relationship between renal parenchymal thickness and the success of operation was found [7]. In our study, patients were evaluated by being grouped according to SSD, which is influenced by obesity and renal parenchymal thickness. The stone-free rate was found to change between 72.8 and 83.3% among the groups, but no statistical significance was recorded. Thus, we can say that SSD did not have an effect on operation success in our study. While some researchers concluded that obesity increases operation time in PCNL [5, 18], El-Assmy et al. [6] showed that neither operation time nor hospitalization time were prolonged by obesity. Carson et al. [19] also reported that obesity did not affect operation and hospitalization times. Tepeler et al. [7] showed that there was no correlation between renal parenchymal thickness and operation, fluoroscopy and hospitalization times. In our study, hospitalization, fluoroscopy and operation times were longer in patients with shorter SSD than in those with longer SSD, but there was no statistical significance. We think that the higher value of stone surface area in group 1 influenced these parameters. According to these results, SSD is not a factor affecting operation, hospitalization and fluoroscopy times. Increased subcutaneous tissue thickness may make it hard to reach the stone with the standard PCNL instruments. While Curtis et al. [20] suggested making an incision on the muscular fascia to facilitate reaching the stone, Giblin et al. [21] proposed to use longer sheaths in obese patients. Fuller et al. [5] showed that the rate of subcostal
renal access increased from 81.2 to 87.4% as obesity increased, and this increase was statistically significant. They reported that this resulted in a decrease in the risk of pulmonary complications, which can be seen in supracostal accesses and can be hardly tolerated by obese patients. In our study, no manipulations were done to shorten the distance to reach the stone in either group. Although we found that the subcostal access rate was higher in patients with longer SSD in our study, it did not reach a statistical significance. None of the patients in both groups had a pulmonary complication due to supracostal access. The CROES Percutaneous Nephrolithotomy Study Group has declared that the rates of hemorrhage and blood transfusion do not increase due to BMI in PCNL operations [5]. El-Assmy et al. [6] also stated that the decrease in hemoglobin does not change as obesity increases. Similar findings were shown in a study with a smaller patient number done by Sergeyev et al. [16]. In their study where the effect of renal parenchymal thickness on PCNL was evaluated, Tepeler et al. [7] found that with the increase in renal parenchymal thickness, the decrease in hemoglobin increased but the blood transfusion rate remained unchanged. Wang et al. [22] also demonstrated that a thick renal parenchyma without hydronephrosis was a risk factor for severe bleeding after PCNL. In our study, no statistical significance was found for the decrease in hemoglobin and blood transfusion rates among the groups. Furthermore, we think that the mild elevation in hemoglobin decrease in patients with shorter SSD is related to longer operation time. Classification of complications after PCNL according to the MCC has recently begun [23, 24]. The CROES Percutaneous Nephrolithotomy Study Group stated that the rate of minor complications (grade 1–2) was lower, while the rate of major complications (grade 3–5) was higher in morbidly obese patients [5]. In addition to this, the need for ureteroscopy or re-PCNL was found to be higher in obese patients [5]. Sergeyev et al. [16] found an increased re-operation risk in obese patients with a stone area >300 mm2. On the other side, while El-Assmy et al. [6] found no difference for postoperative complications and re-operation in obese patients. Tepeler et al. [7] showed that there was no effect of renal parenchymal thickness on complications after PCNL. In our study, no difference was found for complication rates among the groups. Only 2 patients with longer SSD needed a double-J stent due to postoperative clot colic. According to our results, a change in SSD does not affect the safety of the operation.
Skin-to-Stone Distance and Percutaneous Nephrolithotomy
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
447
Acknowledgements
Conclusions
In our study evaluating the relationship between preoperative properties, success and complications of PCNL and SSD, stone-free rates, hospitalization, operation and fluoroscopy times as well as complication rates were not affected by SSD in patients with single renal access. However, we think that the effect of all factors that lead to an increase in SSD should be studied, and patients should be evaluated preoperatively according to these factors. It is also necessary to evaluate the cut-off value of SSD in future studies with a wide range of patients.
The results of this study were presented as a moderated poster (No: MP27-14) at the 30th World Congress of Endourology and SWL which was held on September 4–8, 2012 in Istanbul, Turkey.
Disclosure Statement No conflict of interest exists.
References 1 Fernström I, Johansson B: Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10:257–259. 2 Tiselius HG, Ackermann D, Alken P, et al: Guidelines on Urolithiasis. Arnhem, European Association of Urology, 2007. 3 Deane LA, Clayman RV: Advances in percutaneous nephrostolithotomy. Urol Clin North Am 2007;34:383–395. 4 Thomas R, Cass AS: Extracorporeal shock wave lithotripsy in morbidly obese patients. J Urol 1993;150:30–32. 5 Fuller A, Razvi H, Denstedt JD, Nott L, Pearle M, Cauda F, Bolton D, Celia A, de la Rosette J; CROES PCNL Study Group: The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome. J Urol 2012;188:138–144. 6 El-Assmy AM, Shokeir AA, El-Nahas AR, Shoma AM, Eraky I, El-Kenawy MR, El-Kappany HA: Outcome of percutaneous nephrolithotomy: effect of body mass index. Eur Urol 2007;52:199–204. 7 Tepeler A, Binbay M, Akman T, Erbin A, Kezer C, Silay MS, Yuruk E, Kardas S, Akcay M, Armagan A, Muslumanoglu AY: Parenchymal thickness: does it have an impact on outcomes of percutaneous nephrolithotomy? Urol Int 2013;90:405–410. 8 Park BH, Choi H, Kim JB, Chang YS: Analyzing the effect of distance from skin to stone by computed tomography scan on the extracorporeal shock wave lithotripsy stone-free rate of renal stones. Korean J Urol 2012; 53: 40–43. 9 Perks AE, Schuler TD, Lee J, Ghiculete D, Chung DG, D’A Honey RJ, Pace KT: Stone attenuation and skin-to-stone distance on computed tomography predicts for stone fragmentation by shock wave lithotripsy. Urology 2008;72:765–769.
448
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
10 Pareek G, Hedican SP, Lee FT, Nakada SY: Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005;66:941–944. 11 Tiselius HG, Andersson A: Stone burden in an average Swedish population of stone formers requiring active stone removal: how can the stone size be estimated in the clinical routine? Eur Urol 2003;43:275–281. 12 Dindo D, Demartines N, Clavien PA: Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240:205–213. 13 Amer T, Ahmed K, Bultitude M, Khan S, Kumar P, De Rosa A, Khan MS, Hegarty N: Standard versus tubeless percutaneous nephrolithotomy: a systematic review. Urol Int 2012; 88:373–382. 14 Yoshikawa K, Shimada M, Kurita N, Iwata T, Nishioka M, Morimoto S, Miyatani T, Komatsu M, Mikami C, Kashihara H: Visceral fat area is superior to body mass index as a predictive factor for risk with laparoscopy-assisted gastrectomy for gastric cancer. Surg Endosc 2011;25:3825–3830. 15 Hagiwara M, Miyajima A, Hasegawa M, Jinzaki M, Kikuchi E, Nakagawa K, Oya M: Visceral obesity is a strong predictor of perioperative outcome in patients undergoing laparoscopic radical nephrectomy. BJU Int 2012;110(11 Pt C):E980–E984.
16 Sergeyev I, Koi PT, Jacobs SL, Godelman A, Hoenig DM: Outcome of percutaneous surgery stratified according to body mass index and kidney stone size. Surg Laparosc Endosc Percutan Tech 2007;17:179–183. 17 Bagrodia A, Gupta A, Raman JD, Bensalah K, Pearle MS, Lotan Y: Impact of body mass index on cost and clinical outcomes after percutaneous nephrostolithotomy. Urology 2008; 72:756–760. 18 Pearle MS, Nakada SY, Womack JS, Kryger JV: Outcomes of contemporary percutaneous nephrostolithotomy in morbidly obese patients. J Urol 1998;160:669–673. 19 Carson CC III, Danneberger JE, Weinerth JL: Percutaneous lithotripsy in morbid obesity. J Urol 1988;139:243–245. 20 Curtis R, Thorpe AC, Marsh R: Modification of the technique of percutaneous nephrolithotomy in the morbidly obese patient. Br J Urol 1997;79:138–140. 21 Giblin JG, Lossef S, Pahira JJ: A modification of standard percutaneous nephrolithotripsy technique for the morbidly obese patient. Urology 1995;46:491–493. 22 Wang Y, Jiang F, Wang Y, Hou Y, Zhang H, Chen Q, Xu N, Lu Z, Hu J, Lu J, Wang X, Hao Y, Wang C: Post-percutaneous nephrolithotomy septic shock and severe hemorrhage: a study of risk factors. Urol Int 2012; 88: 307– 310. 23 Tefekli A, Karadag MA, Tepeler K, Sari E, Berberoglu Y, Baykal M, Sarilar O, Muslumanoglu AY: Classification of percutaneous nephrolithotomy complications using the modified Clavien grading system: looking for a standard. Eur Urol 2008;53:184–190. 24 Toksoz S, Dirim A, Kizilkan Y, Ozkardes H: The effect of American Society of Anesthesiology scores on percutaneous nephrolithotomy outcomes. Urol Int 2012;89:301–306.
Gonulalan/Akand/Coban/Cicek/Kosan/ Goktas/Ozkardes
Copyright: S. Karger AG, Basel 2014. Reproduced with the permission of S. Karger AG, Basel. Further reproduction or distribution (electronic or otherwise) is prohibited without permission from the copyright holder.
Urologia Internationalis
Received: August 23, 2013 Accepted after revision: October 22, 2013 Published online: January 29, 2014
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
Skin-to-Stone Distance Has No Impact on Outcomes of Percutaneous Nephrolithotomy Umut Gonulalan a Murat Akand c Gokcen Coban b Tufan Cicek a Murat Kosan a Serdar Goktas c Hakan Ozkardes d Departments of a Urology and b Radiology, Başkent University, and c Department of Urology, Selçuk University, Konya; d Department of Urology, Başkent University, Ankara, Turkey
Key Words Obesity · Percutaneous nephrolithotomy · Skin-to-stone distance · Success
Abstract Objective: Skin-to-stone distance (SSD) is a stronger factor than body mass index in predicting the success of shock wave lithotripsy. We aimed to evaluate the impact of SSD on outcomes of percutaneous nephrolithotomy (PCNL). Materials and Methods: The medical records of 1,280 patients who had undergone PCNL between April 2007 and February 2012 were evaluated retrospectively. 192 patients who had had preoperative non-contrasted computed tomography and single renal access were included the study. According to this median SSD value, patients were divided into two groups: group 1 (SSD ≤94 mm) (n = 92) and group 2 (SSD >94 mm) (n = 90). The groups were compared according to operative and postoperative parameters. Results: We found no significant differences between the two groups with regard to stone-free rate, operation time, fluoroscopy time, hospitalization time, visual analog score of pain, stone burden, transfusion rates and complication rates. On the other hand, the mean body mass index of group 1 was significantly lower than that of group 2 (p < 0.05). Conclusions: In this
© 2014 S. Karger AG, Basel 0042–1138/14/0924–0444$39.50/0 E-Mail [email protected] www.karger.com/uin
retrospective review of patients undergoing PCNL, we found that SSD has no impact on operative and postoperative outcomes. These results were in accordance with the safety of PCNL in obese patients. © 2014 S. Karger AG, Basel
Introduction
Percutaneous nephrolithotomy (PCNL) has been used for stones >2 cm, complicated or staghorn stones in the upper urinary tract since it was first described in 1976 by Fernström and Johansson [1–3]. In the treatment of renal stones in obese patients, extracorporeal shock wave lithotripsy (ESWL) is being used restrictedly due to both weight limitation of the device and larger skin-to-stone distance (SSD), and PCNL is preferred more commonly [4]. Studies evaluating the effect of obesity on the outcomes and complications of PCNL with high caseloads have reported that obesity does not affect the safety of this technique but lowers the stone-free rates [5, 6]. SSD increases due to localization of the stone, increase in subcutaneous and visceral adipose tissue, and thickness of the renal parenchyma. The association between renal parenchymal thickness and the efficacy and safety Umut Gonulalan, MD Başkent University School of Medicine Konya Research and Training Hospital Saray Street, No: 1 Selçuklu, Konya (Turkey) E-Mail drugonulalan @ yahoo.com
of PCNL has been studied by Tepeler et al. [7]. Studies evaluating the effect of SSD on the success of ESWL have demonstrated that increased SSD lowers the stone-free rates after ESWL [8–10]. In those studies, SSD was established as a stronger factor than body mass index (BMI) in predicting the success of ESWL [9, 10]. In this study, we aimed to investigate the effect of SSD on the success and safety of PCNL. Materials and Methods Study Group The files of 1,280 patients who had undergone PCNL due to upper urinary tract stone disease between April 2007 and February 2012 in Başkent University, Konya Practice and Research Center, and Selçuk University, Medical School, Urology Department, were evaluated retrospectively. Exclusion criteria for this study were age 94 mm). Evaluated Data Blood biochemical parameters, complete blood count, demographic properties, operation properties and postoperative complications of the patients were recorded from medical recordings retrospectively. Stone size and area were evaluated with NCCT, and the calculation of stone area was done with the following formula: stone area = length × width × π × 0.25 [11]. Postoperative complications classified according to the modified Clavien classification (MCC) were compared [12]. Surgical Technique First, patients underwent cystoscopy for retrograde catheterization in the lithotomy position under general or spinal anesthesia, and a 5F or 6F ureteral catheter was placed. Afterwards patients were taken into the prone position. The targeted calyx was entered with an 18-gauge needle under bi-planar fluoroscopy, and the tract was dilated to 30F by either balloon or Amplatz dilatators over the guide wire. A standard PCNL procedure was performed, with the lithotripsy done by pneumatic lithotripter, and the stones taken with the grasping forceps. At the end of the operation, the success was evaluated with the help of fluoroscopy. Stones 2 cm, complicated or staghorn stones in the upper urinary tract [1–3, 13]. In the treatment of renal stones in obese patients, PCNL is preferred to ESWL due to long SSD [4]. It has been found that PCNL is safe in obese patients, but with a lower stone-free rate [5, 6]. SSD increases due to localization of the stone, increase in 446
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
subcutaneous and visceral adipose tissue, and thickness of the renal parenchyma. An increase in renal parenchymal thickness does not have an impact on the efficiency and safety of PCNL [7]. In this study, the effect of SSD on the success and safety of PCNL was studied. Although BMI is a widely used index for obesity, various research has shown that visceral adipose tissue is a better deterministic factor for risk than BMI, especially Gonulalan/Akand/Coban/Cicek/Kosan/ Goktas/Ozkardes
in endoscopic operations [14, 15]. In the same way, it has been identified as a stronger factor than BMI in determining the success of ESWL [9, 10]. Also in our study, the BMIs of patients in group 1 (with a shorter SSD) were statistically significantly lower than those of patients in group 2. This result gave rise to the thought that SSD values were increased due to increased visceral and subcutaneous adipose tissue in patients with a higher BMI. BMI can be a determinant factor for surgical outcomes. In their study of 3,709 patients who underwent PCNL and were classified according to their BMI, Fuller et al. [5] reported that the stone-free rate declined from 77.5 to 65.6% as the obesity of the patients increased. On the other hand, El-Assmy et al. [6] stated that obesity did not affect the stone-free rate, which differed between 83.7 and 86.7%. It was supported by other studies with smaller patient numbers [16, 17] that obesity does not have an influence on stone-free rates after PCNL. In another study assessing the effects of renal parenchymal thickness on PCNL outcomes, no relationship between renal parenchymal thickness and the success of operation was found [7]. In our study, patients were evaluated by being grouped according to SSD, which is influenced by obesity and renal parenchymal thickness. The stone-free rate was found to change between 72.8 and 83.3% among the groups, but no statistical significance was recorded. Thus, we can say that SSD did not have an effect on operation success in our study. While some researchers concluded that obesity increases operation time in PCNL [5, 18], El-Assmy et al. [6] showed that neither operation time nor hospitalization time were prolonged by obesity. Carson et al. [19] also reported that obesity did not affect operation and hospitalization times. Tepeler et al. [7] showed that there was no correlation between renal parenchymal thickness and operation, fluoroscopy and hospitalization times. In our study, hospitalization, fluoroscopy and operation times were longer in patients with shorter SSD than in those with longer SSD, but there was no statistical significance. We think that the higher value of stone surface area in group 1 influenced these parameters. According to these results, SSD is not a factor affecting operation, hospitalization and fluoroscopy times. Increased subcutaneous tissue thickness may make it hard to reach the stone with the standard PCNL instruments. While Curtis et al. [20] suggested making an incision on the muscular fascia to facilitate reaching the stone, Giblin et al. [21] proposed to use longer sheaths in obese patients. Fuller et al. [5] showed that the rate of subcostal
renal access increased from 81.2 to 87.4% as obesity increased, and this increase was statistically significant. They reported that this resulted in a decrease in the risk of pulmonary complications, which can be seen in supracostal accesses and can be hardly tolerated by obese patients. In our study, no manipulations were done to shorten the distance to reach the stone in either group. Although we found that the subcostal access rate was higher in patients with longer SSD in our study, it did not reach a statistical significance. None of the patients in both groups had a pulmonary complication due to supracostal access. The CROES Percutaneous Nephrolithotomy Study Group has declared that the rates of hemorrhage and blood transfusion do not increase due to BMI in PCNL operations [5]. El-Assmy et al. [6] also stated that the decrease in hemoglobin does not change as obesity increases. Similar findings were shown in a study with a smaller patient number done by Sergeyev et al. [16]. In their study where the effect of renal parenchymal thickness on PCNL was evaluated, Tepeler et al. [7] found that with the increase in renal parenchymal thickness, the decrease in hemoglobin increased but the blood transfusion rate remained unchanged. Wang et al. [22] also demonstrated that a thick renal parenchyma without hydronephrosis was a risk factor for severe bleeding after PCNL. In our study, no statistical significance was found for the decrease in hemoglobin and blood transfusion rates among the groups. Furthermore, we think that the mild elevation in hemoglobin decrease in patients with shorter SSD is related to longer operation time. Classification of complications after PCNL according to the MCC has recently begun [23, 24]. The CROES Percutaneous Nephrolithotomy Study Group stated that the rate of minor complications (grade 1–2) was lower, while the rate of major complications (grade 3–5) was higher in morbidly obese patients [5]. In addition to this, the need for ureteroscopy or re-PCNL was found to be higher in obese patients [5]. Sergeyev et al. [16] found an increased re-operation risk in obese patients with a stone area >300 mm2. On the other side, while El-Assmy et al. [6] found no difference for postoperative complications and re-operation in obese patients. Tepeler et al. [7] showed that there was no effect of renal parenchymal thickness on complications after PCNL. In our study, no difference was found for complication rates among the groups. Only 2 patients with longer SSD needed a double-J stent due to postoperative clot colic. According to our results, a change in SSD does not affect the safety of the operation.
Skin-to-Stone Distance and Percutaneous Nephrolithotomy
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
447
Acknowledgements
Conclusions
In our study evaluating the relationship between preoperative properties, success and complications of PCNL and SSD, stone-free rates, hospitalization, operation and fluoroscopy times as well as complication rates were not affected by SSD in patients with single renal access. However, we think that the effect of all factors that lead to an increase in SSD should be studied, and patients should be evaluated preoperatively according to these factors. It is also necessary to evaluate the cut-off value of SSD in future studies with a wide range of patients.
The results of this study were presented as a moderated poster (No: MP27-14) at the 30th World Congress of Endourology and SWL which was held on September 4–8, 2012 in Istanbul, Turkey.
Disclosure Statement No conflict of interest exists.
References 1 Fernström I, Johansson B: Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol 1976; 10:257–259. 2 Tiselius HG, Ackermann D, Alken P, et al: Guidelines on Urolithiasis. Arnhem, European Association of Urology, 2007. 3 Deane LA, Clayman RV: Advances in percutaneous nephrostolithotomy. Urol Clin North Am 2007;34:383–395. 4 Thomas R, Cass AS: Extracorporeal shock wave lithotripsy in morbidly obese patients. J Urol 1993;150:30–32. 5 Fuller A, Razvi H, Denstedt JD, Nott L, Pearle M, Cauda F, Bolton D, Celia A, de la Rosette J; CROES PCNL Study Group: The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome. J Urol 2012;188:138–144. 6 El-Assmy AM, Shokeir AA, El-Nahas AR, Shoma AM, Eraky I, El-Kenawy MR, El-Kappany HA: Outcome of percutaneous nephrolithotomy: effect of body mass index. Eur Urol 2007;52:199–204. 7 Tepeler A, Binbay M, Akman T, Erbin A, Kezer C, Silay MS, Yuruk E, Kardas S, Akcay M, Armagan A, Muslumanoglu AY: Parenchymal thickness: does it have an impact on outcomes of percutaneous nephrolithotomy? Urol Int 2013;90:405–410. 8 Park BH, Choi H, Kim JB, Chang YS: Analyzing the effect of distance from skin to stone by computed tomography scan on the extracorporeal shock wave lithotripsy stone-free rate of renal stones. Korean J Urol 2012; 53: 40–43. 9 Perks AE, Schuler TD, Lee J, Ghiculete D, Chung DG, D’A Honey RJ, Pace KT: Stone attenuation and skin-to-stone distance on computed tomography predicts for stone fragmentation by shock wave lithotripsy. Urology 2008;72:765–769.
448
Urol Int 2014;92:444–448 DOI: 10.1159/000356562
10 Pareek G, Hedican SP, Lee FT, Nakada SY: Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005;66:941–944. 11 Tiselius HG, Andersson A: Stone burden in an average Swedish population of stone formers requiring active stone removal: how can the stone size be estimated in the clinical routine? Eur Urol 2003;43:275–281. 12 Dindo D, Demartines N, Clavien PA: Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240:205–213. 13 Amer T, Ahmed K, Bultitude M, Khan S, Kumar P, De Rosa A, Khan MS, Hegarty N: Standard versus tubeless percutaneous nephrolithotomy: a systematic review. Urol Int 2012; 88:373–382. 14 Yoshikawa K, Shimada M, Kurita N, Iwata T, Nishioka M, Morimoto S, Miyatani T, Komatsu M, Mikami C, Kashihara H: Visceral fat area is superior to body mass index as a predictive factor for risk with laparoscopy-assisted gastrectomy for gastric cancer. Surg Endosc 2011;25:3825–3830. 15 Hagiwara M, Miyajima A, Hasegawa M, Jinzaki M, Kikuchi E, Nakagawa K, Oya M: Visceral obesity is a strong predictor of perioperative outcome in patients undergoing laparoscopic radical nephrectomy. BJU Int 2012;110(11 Pt C):E980–E984.
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