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Effect of ureteral access sheath on stone-free rates in patients undergoing ureteroscopic management of renal calculi
ADULT UROLOGY
EFFECT OF URETERAL ACCESS SHEATH ON STONE-FREE RATES IN PATIENTS UNDERGOING URETEROSCOPIC MANAGEMENT OF RENAL CALCULI JAMES O. L’ESPERANCE, WESLEY O. EKERUO, CHARLES D. SCALES, JR, CHARLES G. MARGUET, W. PATRICK SPRINGHART, MICHAELLA E. MALONEY, DAVID M. ALBALA, AND GLENN M. PREMINGER
ABSTRACT Objectives. To evaluate the effect of ureteral access sheaths (UASs) on stone-free rates (SFRs) during ureteroscopic treatment of renal calculi. Several advantages of UASs during flexible ureteroscopy have been documented. However, no study has evaluated their impact on SFRs. Methods. We retrospectively reviewed all ureteroscopic cases for the management of renal stones performed at our Stone Center. Data were stratified according to the use or lack of use of the UAS. The groups were stratified by stone location within the kidney. Stone-free status was determined at 2 months postoperatively by either intravenous urography with tomograms or noncontrast renal computed tomography in patients with contrast allergies. Results. A total of 256 ureteroscopic procedures for the removal of renal calculi were performed between 1997 and 2003 (173 with UAS and 83 without). The groups were similar in age, sex, and stone burden. Stents were placed in nearly 80% of patients. The lower renal pole represented the most common presenting location. Stone displacement with a ureteroscopic basket for efficient fragmentation was necessary in 34%. The overall SFR in the UAS group and non-UAS group was 79% and 67%, respectively (P ⫽ 0.042). The SFRs were improved for calculi in all portions of the kidney. Conclusions. In addition to facilitating ureteroscopic access, reducing costs, and lowering intrarenal pressures, the results of the current study suggest that UASs improve SFRs during the management of renal calculi. It is now our current practice to use the UAS routinely during ureteroscopic treatment of renal and upper ureteral calculi. UROLOGY 66: 252–255, 2005. © 2005 Elsevier Inc.
R
ecent advances in ureteroscopic technology have broadened its use for the management of upper tract stones. These advances include the development of smaller and more durable flexible ureteroscopes with improved optics, as well as improved laser technology and ureteral basket design. Another recent development has been the redesign of ureteral access sheaths (UASs). These
D. M. Albala is a paid consultant to Applied Urology and ACMI. G. M. Preminger is a paid consultant to Olympus America, Boston Scientific, and Mission Pharmacal. From the Comprehensive Kidney Stone Center, Division of Urology, Department of Surgery, Duke University Medical Center, Durham, North Carolina Reprint requests: Glenn M. Preminger, M.D., Division of Urology, Department of Surgery, Duke University Medical Center, Room 1572D, White Zone, DUMC 3167, Durham, NC 27710. E-mail: [email protected] Submitted: December 5, 2004, accepted (with revisions): March 3, 2005 © 2005 ELSEVIER INC. 252
ALL RIGHTS RESERVED
sheaths have been shown to facilitate repetitive upper tract access, reduce intrarenal pressures, decrease operative times, improve visibility, and simplify postoperative stent placement. To date, however, no study has evaluated the impact of UASs on the stone-free rates (SFRs). We evaluated our experience with UASs during the treatment of renal stones, with a specific focus on their impact on SFRs. MATERIAL AND METHODS Data from all patients treated for nephrolithiasis at our Comprehensive Stone Center were entered into a dedicated database, after approval by our institutional review board. A retrospective review of ureteroscopically managed renal stones between January 1997 and May 2003 was performed. The data were separated by the use or lack of use of a UAS. The groups were stratified by stone location within the kidney. Stenting rates and the need to reposition stones in the kidney were also recorded. Stone-free status was determined at 2 0090-4295/05/$30.00 doi:10.1016/j.urology.2005.03.019
months postoperatively by either intravenous urography (IVU) with tomograms or noncontrast renal computed tomography (CT) in patients with contrast allergies or radiolucent stones only. This method of follow-up was maintained throughout the duration of this study. It continues to be our current practice that only patients with contrast allergies or radiolucent stones undergo renal CT; all others undergo IVU with tomograms as follow-up imaging studies. For patient to be considered stone free, they must be completely clear of stones on follow-up studies. Statistical analysis (two tailed chi-square test) was performed with commercially available software. In cases in which the UAS was used, it was nearly always placed at the beginning of the procedure. After the initial safety wire was positioned cystoscopically, the UAS was passed under fluoroscopic guidance. In approximately 10% of cases, the sheath would not pass through the ureteral orifice. In this situation, the dilator was passed alone, and another attempt was made to place the UAS. If the sheath was still met with resistance, balloon dilation of the orifice was performed, after which the access sheath was invariably successfully placed. In general, the sheath was advanced to the proximal ureter. We continue to use 12F to 15F, 35-cm, access sheaths (Applied Medical, Rancho Santa Margarita, Calif, and Boston Scientific, Natick, Mass). In cases in which resistance was met at the level of the iliac vessels, however, we would negotiate the mid and proximal ureter with the flexible ureteroscope instead of further dilating the mid-ureter. In cases in which the UAS was not used, the flexible ureteroscope was placed over a wire under fluoroscopic guidance. Any repositioning or fragmentation was performed at this point. It is generally our practice to attempt fragmentation of the stone down to very small sizes, avoiding the need to basket retrieve stones or fragments through the length of the entire ureter. This has been our practice for both UAS and non-UAS groups.
RESULTS Ureteroscopic manipulation was performed in 256 renal units by a single surgeon (G.M.P.). These cases were divided into those in which a UAS was used (n ⫽ 173) and those in which it was not (n ⫽ 83). The patient population in each group was similar with respect to age, sex, and stone burden, although a trend toward larger stones was noted in the UAS group (8.7 mm versus 7.3 mm, P ⫽ 0.07; Table I). The stone distribution within the kidney was not significantly different between the two groups, with the lower pole representing the most common presenting location (P ⬎0.05; Table II). Repositioning of lower pole stones to the upper or interpolar region of the kidney using a nitinol basket was necessary for 34% of lower pole stones. The holmium:yttrium-aluminum-garnet laser was used in all cases to produce fragments smaller than 2 mm. Basket retrieval of fragments was typically not performed in this series. Ureteral stents were placed in 77% of cases overall, with no significant difference in their use between the two groups. The overall SFR was 75%, with the interpolar region representing the greatest success rates (83%) and the upper pole representing the lowest (62%). The SFR was 79% for cases in which the UROLOGY 66 (2), 2005
TABLE I. Patient demographics, by access sheath use Patients (n) Mean age (yr) Male/female ratio Stone size (mm)
Sheath
No Sheath
P Value
173 49 1.4:1 8.7
83 47 1.3:1 7.3
— 0.17 0.79 0.07
TABLE II. Stone distribution within kidney, by access sheath use
Upper pole Lower pole Interpolar Renal pelvis
Sheath (%)
No Sheath (%)
P Value
19 40 19 22
25 36 17 22
0.51 0.79 0.86 1.0
TABLE III. Stone-free rates by stone location and access sheath use
Upper pole Lower pole Interpolar Renal pelvis Overall
Sheath (%)
No Sheath (%)
P Value
68 79 84 83 79
52 73 79 67 67
0.20 0.35 0.46 0.15 0.04
UAS was used compared with 67% for cases in which the UAS was not used (P ⫽ 0.04). The SFRs were significantly improved when the results from all portions of the kidney were combined. The rates in each specific location were better in the UAS group, although none of these, by themselves, achieved statistical significance (Table III). COMMENT Significant technological advances in ureteroscopy and its instrumentation now afford the endourologist full access to the collecting system. Improved laser and nitinol basket and grasper technology have also furthered ureteroscopic options for the management of upper tract calculi. Another technological advance in ureteroscopic procedures has been the redevelopment of the UAS.1 These sheaths impart several advantages, the first being simplified, repetitive access to the upper tract.2,3 Moreover, the access sheath has been demonstrated to decrease intrarenal pressures during ureteroscopic procedures.4,5 This decrease in pressure not only prevents pyelovenous and pyelosinus backflow, but also provides improved visibility and clearance of small stone fragments. In addition, the UAS has been shown to decrease operative times and 253
TABLE IV. Published stone-free rates, without access sheaths Investigator Sofer et al.21 Harmon et al.20 Bilgasem et al.11 Schuster et al.9 Chow et al.13 Present study
Renal Calculi Stone-Free Rate (%) 84 76 79 77 72 77
costs, facilitate ureteral stent placement, and reduce strain on flexible ureteroscopes.2,6 – 8 Whether these advantages translate into an increased SFR has not been established by prior studies. The current data demonstrated significantly improved SFRs in cases performed with a UAS. Statistical significance was achieved when results in all portions of the kidney were compiled, despite the lack of statistical significance in each specific portion of the kidney. It is important to note that the patients in the UAS group did tend toward larger stone burdens, making the observed improved SFR even more impressive. Several investigators have reported high success rates in treating proximal ureteral and renal calculi ureteroscopically.9 –12 It should be noted that these studies reported the SFR without stating whether access sheaths were used. In addition, the criteria for stone-free status were defined differently in each analysis. In the current study, the overall treatment efficacy in achieving a stone-free state is comparable to the SFR reported in published studies (Table IV). In addition, the stone-free status was clearly defined in this study, with most patients evaluated by IVU with tomograms. Only patients with contrast allergies or radiolucent stones underwent noncontrast renal CT evaluation. Several reasons may explain the slightly reduced SFRs at tertiary care centers, despite the technological advancements in ureteroscopic instrumentation.13 First, the technological advances may contribute to an overall increase in the number of difficult stone cases attempted. Second, these advances afford community urologists the ability to ureteroscopically treat more routine cases, with more complicated patients referred to tertiary centers.14,15 We believe that both of these factors affect the patients seen at our institution. Moreover, the current study used a stringent method to define a stone-free state, because patients must have been completely clear of stones on follow-up imaging studies that included either IVU with tomograms or noncontrast renal CT. Although the results of this study shed light on the impact of the UAS on ureteroscopic management of renal calculi, we also recognize that it had 254
several limitations. As a retrospective analysis, certain biases may have skewed the data. In addition, the practice of repositioning lower pole stones for more efficient fragmentation is a relatively recent development.9,16 –18 As such, this maneuver may have introduced a potential “lower pole bias,” because the non-UAS cases tended to be performed earlier in our series. However, this bias did not affect other presenting stone sites, all of which demonstrated superior SFRs. Another limitation in this study was that many of the non-UAS cases were performed earlier in the study. As such, the development of more modern ureteroscopes, as well as surgeon experience, may also have confounded the data. In terms of surgeon experience, all procedures were performed by the same surgeon who had garnered ample experience before the start of this series. Moreover, it is our impression that the ureteroscopes used have been of similar quality throughout the duration of the study. As the SFRs were superior in all portions of the kidney with use of the access sheaths, improved scope deflection, for instance, would only be expected to enhance lower pole clearance. It should also be noted that stone size was larger in the UAS group, which would serve to balance any technological advantage afforded the later patients. It was also noteworthy that other advances have occurred during the reported period, introducing potential bias. The ideal study would be a randomized controlled study of ureteroscopic procedures performed with and without the UAS. This study would be a difficult study to perform, however, for several reasons. First, several hundred patients would need to be enrolled to power the study adequately. Second, it would take several years to complete, and the results would be skewed by the same limitations seen in the current investigation. Namely, additional advances in technology will continue and inevitably make data analysis difficult and subject to bias. Third, several advantages to the UAS have already been described in published reports. The accrual of patients might be difficult because many would be unwilling to undergo ureteroscopy without the latest technology. As a result of these limitations, obviating the possibility of performing a rigidly controlled study, it is reasonable to look at retrospective data. The current study was substantial in size and the results have clearly indicated that the UAS has advantages in terms of SFRs. The current study also focused on the indications for using ureteroscopy to manage symptomatic renal calculi and whether these indications should be expanded. Recent studies have suggested that efficacy rates are improving and complication rates declining with the ureteroscopic management of upper tract stones.13 In addition, UROLOGY 66 (2), 2005
the SFRs after shock wave lithotripsy management of renal calculi have been diminishing, because of the lower power and tighter focal zones of newer lithotriptors.19 Although some investigators have supported the pursuit of renal stones in the setting of concurrent ureteral calculi or other ureteral pathologic features, others have recommended ureteroscopic management of renal or upper ureteral stones as primary therapy.9 –11,13,20 –23 In the current study, we documented an adequate success rate in all portions of the kidney. Thus, we have increased our application of flexible ureteroscopy for the management of symptomatic renal calculi. CONCLUSIONS UASs offer several advantages, including simplified repetitive access, decreased intrarenal pressures, improved visibility, prolonged ureteroscope life, and simplified stent placement. The results of the current study have suggested that routine use of a UAS may also improve SFRs in patients with renal calculi managed ureteroscopically. It is currently our practice to use a UAS routinely during the ureteroscopic management of renal calculi. REFERENCES 1. Andreoni C, Portis AJ, and Clayman RV: Retrograde renal pelvic access sheath to facilitate flexible ureteroscopic lithotripsy for the treatment of urolithiasis in a horseshoe kidney. J Urol 164: 1290 –1291, 2000. 2. Kourambas J, Byrne RR, and Preminger GM: Does a ureteral access sheath facilitate ureteroscopy? J Urol 165: 789 –793, 2001. 3. Monga M, Bhayani S, Landman J, et al: Ureteral access for upper urinary tract disease: the access sheath. J Endourol 15: 831– 834, 2001. 4. Rehman J, Monga M, Landman J, et al: Characterization of intrapelvic pressure during ureteropyeloscopy with ureteral access sheaths. Urology 61: 713–718, 2003. 5. Auge BK, Pietrow PK, Lallas CD, et al: Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol 18: 33–36, 2004. 6. Wu NZ, Auge BK, and Preminger GM: Simplified ureteral stent placement with the assistance of a ureteral access sheath. J Urol 166: 206 –208, 2001.
UROLOGY 66 (2), 2005
7. Delvecchio FC, Auge BK, Brizuela RM, et al: Assessment of stricture formation with the ureteral access sheath. Urology 61: 518 –522, 2003. 8. Pietrow PK, Auge BK, Delvecchio FC, et al: Techniques to maximize flexible ureteroscope longevity. Urology 60: 784 –788, 2002. 9. Schuster TG, Hollenbeck BK, Faerber GJ, et al: Ureteroscopic treatment of lower pole calculi: comparison of lithotripsy in situ and after displacement. J Urol 168: 43– 45, 2002. 10. Zheng W, Beiko DT, Segura JW, et al: Urinary calculi in aviation pilots: what is the best therapeutic approach? J Urol 168: 1341–1343, 2002. 11. Bilgasem S, Pace KT, Dyer S, et al: Removal of asymptomatic ipsilateral renal stones following rigid ureteroscopy for ureteral stones. J Endourol 17: 397– 400, 2003. 12. Hollenbeck BK, Schuster TG, Faerber GJ, et al: Safety and efficacy of same-session bilateral ureteroscopy. J Endourol 17: 881– 885, 2003. 13. Chow GK, Patterson DE, Blute ML, et al: Ureteroscopy: effect of technology and technique on clinical practice. J Urol 170: 99 –102, 2003. 14. Grasso M, Beaghler M, and Loisides P: The case for primary endoscopic management of upper urinary tract calculi: II. Cost and outcome assessment of 112 primary ureteral calculi. Urology 45: 372–376, 1995. 15. Loisides P, Grasso M, and Lui P: Laparoscopic cutaneous ureterostomy: technique for palliative upper urinary tract drainage. J Endourol 9: 315–317, 1995. 16. Hollenbeck BK, Schuster TG, Faerber GJ, et al: Flexible ureteroscopy in conjunction with in situ lithotripsy for lower pole calculi. Urology 58: 859 – 863, 2001. 17. Kourambas J, Delvecchio FC, Munver R, et al: Nitinol stone retrieval-assisted ureteroscopic management of lower pole renal calculi. Urology 56: 935–939, 2000. 18. Auge BK, Dahm P, Wu NZ, et al: Ureteroscopic management of lower-pole renal calculi: technique of calculus displacement. J Endourol 15: 835– 838, 2001. 19. Lingeman JE, Kim SC, Kuo RL, et al: Shockwave lithotripsy: anecdotes and insights. J Endourol 17: 687– 693, 2003. 20. Harmon WJ, Sershon PD, Blute ML, et al: Ureteroscopy: current practice and long-term complications. J Urol 157: 28 – 32, 1997. 21. Sofer M, Watterson JD, Wollin TA, et al: Holmium:YAG laser lithotripsy for upper urinary tract calculi in 598 patients. J Urol 167: 31–34, 2002. 22. Watterson JD, Girvan AR, Cook AJ, et al: Safety and efficacy of holmium:YAG laser lithotripsy in patients with bleeding diatheses. J Urol 168: 442– 445, 2002. 23. Auge BK, Munver R, Kourambas J, et al: Endoscopic management of symptomatic caliceal diverticula: a retrospective comparison of percutaneous nephrolithotripsy and ureteroscopy. J Endourol 16: 557–564, 2002.
255
EFFECT OF URETERAL ACCESS SHEATH ON STONE-FREE RATES IN PATIENTS UNDERGOING URETEROSCOPIC MANAGEMENT OF RENAL CALCULI JAMES O. L’ESPERANCE, WESLEY O. EKERUO, CHARLES D. SCALES, JR, CHARLES G. MARGUET, W. PATRICK SPRINGHART, MICHAELLA E. MALONEY, DAVID M. ALBALA, AND GLENN M. PREMINGER
ABSTRACT Objectives. To evaluate the effect of ureteral access sheaths (UASs) on stone-free rates (SFRs) during ureteroscopic treatment of renal calculi. Several advantages of UASs during flexible ureteroscopy have been documented. However, no study has evaluated their impact on SFRs. Methods. We retrospectively reviewed all ureteroscopic cases for the management of renal stones performed at our Stone Center. Data were stratified according to the use or lack of use of the UAS. The groups were stratified by stone location within the kidney. Stone-free status was determined at 2 months postoperatively by either intravenous urography with tomograms or noncontrast renal computed tomography in patients with contrast allergies. Results. A total of 256 ureteroscopic procedures for the removal of renal calculi were performed between 1997 and 2003 (173 with UAS and 83 without). The groups were similar in age, sex, and stone burden. Stents were placed in nearly 80% of patients. The lower renal pole represented the most common presenting location. Stone displacement with a ureteroscopic basket for efficient fragmentation was necessary in 34%. The overall SFR in the UAS group and non-UAS group was 79% and 67%, respectively (P ⫽ 0.042). The SFRs were improved for calculi in all portions of the kidney. Conclusions. In addition to facilitating ureteroscopic access, reducing costs, and lowering intrarenal pressures, the results of the current study suggest that UASs improve SFRs during the management of renal calculi. It is now our current practice to use the UAS routinely during ureteroscopic treatment of renal and upper ureteral calculi. UROLOGY 66: 252–255, 2005. © 2005 Elsevier Inc.
R
ecent advances in ureteroscopic technology have broadened its use for the management of upper tract stones. These advances include the development of smaller and more durable flexible ureteroscopes with improved optics, as well as improved laser technology and ureteral basket design. Another recent development has been the redesign of ureteral access sheaths (UASs). These
D. M. Albala is a paid consultant to Applied Urology and ACMI. G. M. Preminger is a paid consultant to Olympus America, Boston Scientific, and Mission Pharmacal. From the Comprehensive Kidney Stone Center, Division of Urology, Department of Surgery, Duke University Medical Center, Durham, North Carolina Reprint requests: Glenn M. Preminger, M.D., Division of Urology, Department of Surgery, Duke University Medical Center, Room 1572D, White Zone, DUMC 3167, Durham, NC 27710. E-mail: [email protected] Submitted: December 5, 2004, accepted (with revisions): March 3, 2005 © 2005 ELSEVIER INC. 252
ALL RIGHTS RESERVED
sheaths have been shown to facilitate repetitive upper tract access, reduce intrarenal pressures, decrease operative times, improve visibility, and simplify postoperative stent placement. To date, however, no study has evaluated the impact of UASs on the stone-free rates (SFRs). We evaluated our experience with UASs during the treatment of renal stones, with a specific focus on their impact on SFRs. MATERIAL AND METHODS Data from all patients treated for nephrolithiasis at our Comprehensive Stone Center were entered into a dedicated database, after approval by our institutional review board. A retrospective review of ureteroscopically managed renal stones between January 1997 and May 2003 was performed. The data were separated by the use or lack of use of a UAS. The groups were stratified by stone location within the kidney. Stenting rates and the need to reposition stones in the kidney were also recorded. Stone-free status was determined at 2 0090-4295/05/$30.00 doi:10.1016/j.urology.2005.03.019
months postoperatively by either intravenous urography (IVU) with tomograms or noncontrast renal computed tomography (CT) in patients with contrast allergies or radiolucent stones only. This method of follow-up was maintained throughout the duration of this study. It continues to be our current practice that only patients with contrast allergies or radiolucent stones undergo renal CT; all others undergo IVU with tomograms as follow-up imaging studies. For patient to be considered stone free, they must be completely clear of stones on follow-up studies. Statistical analysis (two tailed chi-square test) was performed with commercially available software. In cases in which the UAS was used, it was nearly always placed at the beginning of the procedure. After the initial safety wire was positioned cystoscopically, the UAS was passed under fluoroscopic guidance. In approximately 10% of cases, the sheath would not pass through the ureteral orifice. In this situation, the dilator was passed alone, and another attempt was made to place the UAS. If the sheath was still met with resistance, balloon dilation of the orifice was performed, after which the access sheath was invariably successfully placed. In general, the sheath was advanced to the proximal ureter. We continue to use 12F to 15F, 35-cm, access sheaths (Applied Medical, Rancho Santa Margarita, Calif, and Boston Scientific, Natick, Mass). In cases in which resistance was met at the level of the iliac vessels, however, we would negotiate the mid and proximal ureter with the flexible ureteroscope instead of further dilating the mid-ureter. In cases in which the UAS was not used, the flexible ureteroscope was placed over a wire under fluoroscopic guidance. Any repositioning or fragmentation was performed at this point. It is generally our practice to attempt fragmentation of the stone down to very small sizes, avoiding the need to basket retrieve stones or fragments through the length of the entire ureter. This has been our practice for both UAS and non-UAS groups.
RESULTS Ureteroscopic manipulation was performed in 256 renal units by a single surgeon (G.M.P.). These cases were divided into those in which a UAS was used (n ⫽ 173) and those in which it was not (n ⫽ 83). The patient population in each group was similar with respect to age, sex, and stone burden, although a trend toward larger stones was noted in the UAS group (8.7 mm versus 7.3 mm, P ⫽ 0.07; Table I). The stone distribution within the kidney was not significantly different between the two groups, with the lower pole representing the most common presenting location (P ⬎0.05; Table II). Repositioning of lower pole stones to the upper or interpolar region of the kidney using a nitinol basket was necessary for 34% of lower pole stones. The holmium:yttrium-aluminum-garnet laser was used in all cases to produce fragments smaller than 2 mm. Basket retrieval of fragments was typically not performed in this series. Ureteral stents were placed in 77% of cases overall, with no significant difference in their use between the two groups. The overall SFR was 75%, with the interpolar region representing the greatest success rates (83%) and the upper pole representing the lowest (62%). The SFR was 79% for cases in which the UROLOGY 66 (2), 2005
TABLE I. Patient demographics, by access sheath use Patients (n) Mean age (yr) Male/female ratio Stone size (mm)
Sheath
No Sheath
P Value
173 49 1.4:1 8.7
83 47 1.3:1 7.3
— 0.17 0.79 0.07
TABLE II. Stone distribution within kidney, by access sheath use
Upper pole Lower pole Interpolar Renal pelvis
Sheath (%)
No Sheath (%)
P Value
19 40 19 22
25 36 17 22
0.51 0.79 0.86 1.0
TABLE III. Stone-free rates by stone location and access sheath use
Upper pole Lower pole Interpolar Renal pelvis Overall
Sheath (%)
No Sheath (%)
P Value
68 79 84 83 79
52 73 79 67 67
0.20 0.35 0.46 0.15 0.04
UAS was used compared with 67% for cases in which the UAS was not used (P ⫽ 0.04). The SFRs were significantly improved when the results from all portions of the kidney were combined. The rates in each specific location were better in the UAS group, although none of these, by themselves, achieved statistical significance (Table III). COMMENT Significant technological advances in ureteroscopy and its instrumentation now afford the endourologist full access to the collecting system. Improved laser and nitinol basket and grasper technology have also furthered ureteroscopic options for the management of upper tract calculi. Another technological advance in ureteroscopic procedures has been the redevelopment of the UAS.1 These sheaths impart several advantages, the first being simplified, repetitive access to the upper tract.2,3 Moreover, the access sheath has been demonstrated to decrease intrarenal pressures during ureteroscopic procedures.4,5 This decrease in pressure not only prevents pyelovenous and pyelosinus backflow, but also provides improved visibility and clearance of small stone fragments. In addition, the UAS has been shown to decrease operative times and 253
TABLE IV. Published stone-free rates, without access sheaths Investigator Sofer et al.21 Harmon et al.20 Bilgasem et al.11 Schuster et al.9 Chow et al.13 Present study
Renal Calculi Stone-Free Rate (%) 84 76 79 77 72 77
costs, facilitate ureteral stent placement, and reduce strain on flexible ureteroscopes.2,6 – 8 Whether these advantages translate into an increased SFR has not been established by prior studies. The current data demonstrated significantly improved SFRs in cases performed with a UAS. Statistical significance was achieved when results in all portions of the kidney were compiled, despite the lack of statistical significance in each specific portion of the kidney. It is important to note that the patients in the UAS group did tend toward larger stone burdens, making the observed improved SFR even more impressive. Several investigators have reported high success rates in treating proximal ureteral and renal calculi ureteroscopically.9 –12 It should be noted that these studies reported the SFR without stating whether access sheaths were used. In addition, the criteria for stone-free status were defined differently in each analysis. In the current study, the overall treatment efficacy in achieving a stone-free state is comparable to the SFR reported in published studies (Table IV). In addition, the stone-free status was clearly defined in this study, with most patients evaluated by IVU with tomograms. Only patients with contrast allergies or radiolucent stones underwent noncontrast renal CT evaluation. Several reasons may explain the slightly reduced SFRs at tertiary care centers, despite the technological advancements in ureteroscopic instrumentation.13 First, the technological advances may contribute to an overall increase in the number of difficult stone cases attempted. Second, these advances afford community urologists the ability to ureteroscopically treat more routine cases, with more complicated patients referred to tertiary centers.14,15 We believe that both of these factors affect the patients seen at our institution. Moreover, the current study used a stringent method to define a stone-free state, because patients must have been completely clear of stones on follow-up imaging studies that included either IVU with tomograms or noncontrast renal CT. Although the results of this study shed light on the impact of the UAS on ureteroscopic management of renal calculi, we also recognize that it had 254
several limitations. As a retrospective analysis, certain biases may have skewed the data. In addition, the practice of repositioning lower pole stones for more efficient fragmentation is a relatively recent development.9,16 –18 As such, this maneuver may have introduced a potential “lower pole bias,” because the non-UAS cases tended to be performed earlier in our series. However, this bias did not affect other presenting stone sites, all of which demonstrated superior SFRs. Another limitation in this study was that many of the non-UAS cases were performed earlier in the study. As such, the development of more modern ureteroscopes, as well as surgeon experience, may also have confounded the data. In terms of surgeon experience, all procedures were performed by the same surgeon who had garnered ample experience before the start of this series. Moreover, it is our impression that the ureteroscopes used have been of similar quality throughout the duration of the study. As the SFRs were superior in all portions of the kidney with use of the access sheaths, improved scope deflection, for instance, would only be expected to enhance lower pole clearance. It should also be noted that stone size was larger in the UAS group, which would serve to balance any technological advantage afforded the later patients. It was also noteworthy that other advances have occurred during the reported period, introducing potential bias. The ideal study would be a randomized controlled study of ureteroscopic procedures performed with and without the UAS. This study would be a difficult study to perform, however, for several reasons. First, several hundred patients would need to be enrolled to power the study adequately. Second, it would take several years to complete, and the results would be skewed by the same limitations seen in the current investigation. Namely, additional advances in technology will continue and inevitably make data analysis difficult and subject to bias. Third, several advantages to the UAS have already been described in published reports. The accrual of patients might be difficult because many would be unwilling to undergo ureteroscopy without the latest technology. As a result of these limitations, obviating the possibility of performing a rigidly controlled study, it is reasonable to look at retrospective data. The current study was substantial in size and the results have clearly indicated that the UAS has advantages in terms of SFRs. The current study also focused on the indications for using ureteroscopy to manage symptomatic renal calculi and whether these indications should be expanded. Recent studies have suggested that efficacy rates are improving and complication rates declining with the ureteroscopic management of upper tract stones.13 In addition, UROLOGY 66 (2), 2005
the SFRs after shock wave lithotripsy management of renal calculi have been diminishing, because of the lower power and tighter focal zones of newer lithotriptors.19 Although some investigators have supported the pursuit of renal stones in the setting of concurrent ureteral calculi or other ureteral pathologic features, others have recommended ureteroscopic management of renal or upper ureteral stones as primary therapy.9 –11,13,20 –23 In the current study, we documented an adequate success rate in all portions of the kidney. Thus, we have increased our application of flexible ureteroscopy for the management of symptomatic renal calculi. CONCLUSIONS UASs offer several advantages, including simplified repetitive access, decreased intrarenal pressures, improved visibility, prolonged ureteroscope life, and simplified stent placement. The results of the current study have suggested that routine use of a UAS may also improve SFRs in patients with renal calculi managed ureteroscopically. It is currently our practice to use a UAS routinely during the ureteroscopic management of renal calculi. REFERENCES 1. Andreoni C, Portis AJ, and Clayman RV: Retrograde renal pelvic access sheath to facilitate flexible ureteroscopic lithotripsy for the treatment of urolithiasis in a horseshoe kidney. J Urol 164: 1290 –1291, 2000. 2. Kourambas J, Byrne RR, and Preminger GM: Does a ureteral access sheath facilitate ureteroscopy? J Urol 165: 789 –793, 2001. 3. Monga M, Bhayani S, Landman J, et al: Ureteral access for upper urinary tract disease: the access sheath. J Endourol 15: 831– 834, 2001. 4. Rehman J, Monga M, Landman J, et al: Characterization of intrapelvic pressure during ureteropyeloscopy with ureteral access sheaths. Urology 61: 713–718, 2003. 5. Auge BK, Pietrow PK, Lallas CD, et al: Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol 18: 33–36, 2004. 6. Wu NZ, Auge BK, and Preminger GM: Simplified ureteral stent placement with the assistance of a ureteral access sheath. J Urol 166: 206 –208, 2001.
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