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Impact of Preoperative Ureteral Stenting on Outcome of Ureteroscopic Treatment for Urinary Lithiasis
Impact of Preoperative Ureteral Stenting on Outcome of Ureteroscopic Treatment for Urinary Lithiasis John M. Shields, Vincent G. Bird,*,† Reid Graves and Orlando Gómez-Marín From the Departments of Urology, Epidemiology and Public Health (OGM), Pediatrics (OGM) and Medicine (OGM), Miller School of Medicine, University of Miami, Miami, Florida
Abbreviations and Acronyms DU ⫽ distal ureter PU ⫽ proximal ureter SFR ⫽ stone-free rate SWL ⫽ shock wave lithotripsy UAS ⫽ ureteral access sheath Submitted for publication April 6, 2009. Study received institutional review board approval. * Correspondence: Division of Endourology and Laparoscopy, Department of Urology, Miller School of Medicine, University of Miami, Dominion Tower, Suite 509 (M814), Miami, Florida 33136 (telephone: 305-243-7261; FAX: 305-2433381; e-mail: [email protected]). † Financial interest and/or other relationship with Applied Medical.
Purpose: Sparse published data exist on the impact of preexistent ureteral stents on the success of ureteroscopic stone surgery. We investigated the impact of a preexistent ureteral stent in relation to a number of parameters and outcomes of ureteroscopic management for urinary lithiasis. Materials and Methods: We retrospectively evaluated a cohort of patients undergoing ureteroscopy for renal and ureteral calculi. Data were abstracted on stone side, size, number and site, patient demographics, total stone burden, ureteral access sheath use, preoperative ureteral stent, ureteroscope type and outcome. Statistical analysis was done. Results: The success rate of 1 and 2 ureteroscopic procedures was 86.9% and 97.3%, respectively. Primary analysis included data on 221 initial procedures. The single procedure success rate for stone site was 91.9% for the distal ureter, 89.7% for the proximal ureter, 83.3% for the renal pelvis, 80.5% for the lower pole and 82.4% for the interpolar/upper pole. Success was negatively associated with primary stone size (p ⫽ 0.020), total stone number (p ⫽ 0.001) and cumulative stone burden (p ⬍0.001). Stone site was not a predictor of success (p ⫽ 0.394). A preexistent stent was positively associated with success but it was not statistically significant (adjusted OR 2.22; 95% CI 0.88, 5.63; p ⫽ 0.254). Secondary analysis in patients who initially underwent flexible ureteroscopy yielded results consistent with those of primary analysis. Conclusions: Results show that ureteropyeloscopic lithotripsy and stone extraction may be performed with a high success rate. Success was significantly inversely related to stone size, cumulative stone burden and number of stones. Success was positively related to a preexisting ureteral stent but not significantly so. Key Words: ureter, ureteroscopy, stents, urolithiasis, lithotripsy
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URETERAL stents are commonly used with various treatment modalities for urinary lithiasis. Stents are useful to prevent the postoperative colic that may be due to passage of residual stones/debris and transient postoperative edema. However, although these devices are useful for these purposes, they are not free of undesirable effects. Stents are associated with various urinary tract symptoms, including flank
pain/discomfort, urinary frequency and dysuria.1– 4 A large number of studies describe postoperative ureteral stenting. However, there are limited data on the impact on surgical outcome when ureteral stents are present before the ureteroscopic procedure. Stents are often placed in emergent scenarios for acute ureteral obstruction, which may be associated with infection or other
0022-5347/09/1826-2768/0 THE JOURNAL OF UROLOGY® Copyright © 2009 by AMERICAN UROLOGICAL ASSOCIATION
Vol. 182, 2768-2774, December 2009 Printed in U.S.A. DOI:10.1016/j.juro.2009.08.043
URETERAL STENTING AND URETEROSCOPIC TREATMENT FOR URINARY LITHIASIS
conditions that preclude immediate definitive management for a stone. They may also be placed in conjunction with SWL or ureteroscopy. Indwelling ureteral stents that may passively dilate the ureter have been used in pediatric urology patients, who often have small caliber ureters.5 However, the impact of preexistent ureteral stents on success in the general population is not clear. We investigated whether preexistent stents have an impact on SFR after ureteroscopy.
MATERIALS AND METHODS Internal review board approval was obtained at our institution before the study. We reviewed our database of patients who underwent retrograde ureteroscopy for ureteral and renal calculi, as done by 1 surgeon between 2002 and 2007. Patients with solitary as well as multiple renal calculi were included in analysis, as were patients in whom previous extracorporeal SWL failed. Patients treated as part of percutaneous procedures were excluded from study. We abstracted data on stone site, size and number, patient demographics, preexisting ureteral stent, intraoperative UAS use, ureteroscope type and model, number of treatments needed to attain stone-free status and treatment success, defined as stone-free status using radiographic criteria. Stone number was coded according to the number of stones as 1, 2, 3 or multiple (coded as 4) when more than 3 stones were present. In multiple stone cases the 3 largest stones were considered for stone site and burden. The latter was defined as the sum in cm of the size of the 3 largest stones. Stone site was coded as 1—DU and/or ureterovesical junction, 2—PU and/or mid ureter, 3— renal pelvis and/or ureteropelvic junction, 4 —lower pole, and 5—interpolar and/or upper pole. DU defined all stones from the ureterovesical junction to the level of the ureter where it crosses the iliac vessels. Mid ureter and PU defined all ureteral stones in the ureter above the iliac vessels up to but not including the ureteropelvic junction.
Treatment Various ureteroscopes were used for ureteroscopic procedures, including ACMI™ MR6 semirigid ureteroscopes, and AUR7, AUR 9, DUR™-8, DUR8 Elite, Karl Storz™ 11274AA, Flex-X™ and Flex X2™ flexible ureteroscopes. All ureteroscopic procedures were performed with guidewires, including a safety wire. Intact stone retrieval, intracorporeal lithotripsy and UAS use were done at surgeon discretion. Ancillary devices included UASs, laser fibers and stone retrieval baskets. UASs included the Forte® with an inner and outer diameter of 12Fr and 14Fr, the Forte XE with an inner and outer diameter of 12Fr and 15Fr, and the Uropass™ with an inner and outer diameter of 12Fr and 14Fr, respectively. Laser fibers included the Coherent® 200 and 365 , the Dornier® 270 , and the AccuFlex™ 200 and ACMI 270 holmium light guide laser fibers. Laser generators used included the VersaPulse®, the mediLAS® H20 and the VersaPulse PowerSuite™ 20 W
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holmium laser. Also used were 1.9Fr and 2.4Fr ZeroTip™ nitinol stone retrieval baskets. Patients were treated primarily with semirigid or flexible ureteroscopy. In cases of semirigid ureteroscopy when suspicion arose that stone fragments had migrated proximal, a flexible scope was used to investigate this possibility and any migrated fragments were removed. In cases of poor visualization, significant edema or persistent extensive stone burden after extensive lithotripsy and stone extraction at surgeon discretion the ureteroscopic procedure was terminated. Ureteral stents were placed at the end of all ureteroscopic procedures.
Followup All patients were seen within 1 to 6 weeks after treatment. All patients underwent radiographic imaging within 1 to 12 weeks after treatment by stone protocol noncontrast computerized tomography (3 mm cuts) and plain x-ray at 1 of 2 health care institutions. Radiographic success was defined as the absence of any stone material. One mm punctate calcifications occasionally seen in the region of the renal papillae were not considered urinary drainage tract stones.
Statistical Methods Statistical methods used focused mainly on comparing patients with vs without a preoperative stent. These 2 groups were compared for age using the independent sample t test and for stone burden (a variable with a highly skewed distribution) using the Mann-Whitney test. Chisquare analysis was done to assess associations between discrete variables. Simple and multiple logistic regression analyses were used to assess preoperative stents and other variables, combinations thereof and their interactions as predictors of success.
RESULTS A total of 259 ureteroscopies were performed during the study period. To preserve statistical independence 13 patients with bilateral ureteroscopic procedures had only data from 1 side chosen at random included in analysis. The figure shows the clinical outcome in all patients. The success rate after 1 ureteroscopic procedure was 86.9%, which increased to 97.3% after 2 ureteroscopic procedures. Of the 221 patients with success after only 1 ureteroscopic procedure (192), failure after only 1 (4) and a failed first ureteroscopic procedure (25) 150 had a stent preoperatively (see figure). Of the patients 71 had no preexisting stent. Table 1 lists characteristics in these 221 patients and their relationship to preoperative stent status. There were no statistically significant differences between patients with vs without a preoperative stent for age (p ⫽ 0.319), primary stone size (p ⫽ 0.417), stone burden (p ⫽ 0.982), gender (p ⫽ 0.631), surgery side (p ⫽ 0.359), total number of stones (p ⫽ 0.112) or success rate (p ⫽ 0.252). However, primary stone site was significantly associated with a preoperative stent, ranging from 51.6% in patients with the primary
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Success and failure in patients with 1 and 2 procedures with success rate calculated as (192)/(192 ⫹ 4 ⫹ 25) ⫽ 86.9% and (192 ⫹ 23)/ (192 ⫹ 23 ⫹ 4 ⫹ 2) ⫽ 97.3%, respectively.
stone at site 1 to 79.2% in those with the primary stone at site 3 (p ⫽ 0.026). The proportion of patients with a preoperative stent was significantly higher in those who underwent flexible vs semirigid ureteroscopy (73.3% vs 60.0%, p ⫽ 0.038). Table 2 shows bivariate analysis of success rates. Success, defined as stone-free status, was not significantly related to age (p ⫽ 0.290), gender (p ⫽ 0.757) or surgery side (p ⫽ 0.890). Success was not significantly related to primary stone location (p ⫽ 0.394) but the success rate ranged from 80.5% for site 4 to 91.9% for site 1 (table 2). A preexisting stent was positively associated with success but this did not attain statistical significance (with vs without a stent 88.7% vs 83.1%, p ⫽ 0.254). Compared with the 29 failed cases the 192 with a successful outcome had significantly smaller primary stone size (mean ⫾ SD 0.9 ⫾ 0.6 vs 1.3 ⫾ 0.8 cm, p ⫽ 0.004) and a lower stone burden (1.1 ⫾ 0.7 vs 2.1 ⫾ 1.0 cm, p ⬍0.001). Success was significantly inversely related to stone number (p ⬍0.001). The success rates decreased linearly from 92.4% in patients with only 1 stone to 60.9% in those with 4 or more (table 2). A flexible ureteroscope was negatively related to success. The success rate was 80.9% vs 95.6% in those primarily treated with a flexible vs a semirigid ureteroscope (table 2). To assess different covariates as potential predictors of successful ureteroscopy bivariate and multivariate logistic regression analyses were done. Table 3 lists the results of separate regression models with the estimated ORs, and corresponding 95% CIs and p values. Statistically significant predictors of failure (OR ⬍1.00) were primary stone size (p ⫽ 0.006), stone burden (p ⬍0.001) and stone number (p ⬍0.001). A preoperative stent was not signif-
icantly related to success but patients with a stent were 59% more likely to achieve success than patients without a stent (table 3). To account for the interrelationship between potential confounders several multivariate models were considered, of which all included a preoperative stent as a forced variable. Table 3 also shows results of the final model using stepwise logistic regression. Results agree with those of the separate models but after adjusting for stone burden and stone number the odds of success in patients with a preoperative stent increased from 1.59 to 2.2 (table 3). Separate analysis, including bivariate and multivariate analyses, was done in 131 patients who underwent flexible ureteroscopy only. On logistic regression analysis primary stone size (p ⬍0.0001), cumulative stone burden (p ⬍0.0001) and stone number (p ⫽ 0.0009) were again negatively associated with success. These results correlated with the analysis in the entire group.
DISCUSSION Ureterorenoscopy is effective for ureteral and renal calculi, and high success rates have been reported.6 – 8 On a meta-analysis ureteroscopy resulted in a higher SFR than SWL for ureteral calculi.7 A systematic review by Rubenstein et al also showed that ureteroscopic removal of ureteral stones achieves a higher SFR than SWL.9 Although there are numerous studies of ureteroscopic management for urinary calculi, few acknowledge or address preoperatively placed stents and their impact on surgical outcome (table 4). The potential impact of ureteral stenting on ureteroscopic procedures is an impor-
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Table 1. Patient age and clinical characteristics by preoperative stent group Characteristic
Total No. (%)
No Preop Stent
Preop Stent
p Value
Mean ⫾ SD age Mean ⫾ SD stone burden (cm) No. gender (%): M F Side: Rt Lt No. stones (%): 1 2 3 4 or Greater No. stone 1 site (%): 1 2 3 4 5 No. stone-free (%): Yes No No. flexible scope (%): Yes No No. UAS (%): Yes No No. scope type (%): Flexible Semirigid Flexible ⫹ semirigid No. semirigid scope (%): Yes No No. stone-free, no flexible scope (%): Yes No No. stone-free, flexible scope (%): Yes No
50.6 ⫾ 13.2 1.3 ⫾ 0.8
49.3 ⫾ 14.9 1.2 ⫾ 0.7
51.3 ⫾ 12.4 1.3 ⫾ 0.8
0.319 (unequal variance 2-sample t test) 0.982 (Mann-Whitney U test) 0.631
145 (65.6) 76 (34.4)
45 (31.0) 26 (34.2)
100 (69.0) 50 (65.8)
96 (43.4) 125 (56.6)
34 (35.4) 37 (29.6)
62 (64.6) 88 (70.4)
145 (65.6) 27 (12.2) 26 (11.8) 23 (10.4)
52 (35.9) 6 (22.2) 4 (15.4) 9 (39.1)
93 (64.1) 21 (77.8) 22 (84.6) 14 (60.7)
62 (28.1) 58 (26.2) 24 (10.9) 43 (19.5) 34 (15.3)
30 (48.4) 14 (24.1) 5 (20.8) 13 (30.2) 9 (26.5)
32 (51.6) 44 (75.9) 19 (79.2) 30 (69.8) 25 (73.5)
192 (86.9) 29 (13.1)
59 (30.7) 12 (41.4)
133 (69.3) 17 (58.6)
131 (59.3) 90 (40.7)
35 (26.7) 36 (40.0)
96 (73.3) 54 (60.0)
111 (50.2) 110 (49.8)
25 (22.5) 46 (41.8)
86 (77.5) 64 (58.2)
131 (59.3) 52 (23.5) 38 (17.2)
35 (26.7) 26 (50.0) 10 (26.3)
96 (73.3) 26 (50.0) 28 (73.7)
52 (23.5) 169 (76.5)
26 (50.0) 45 (26.6)
26 (50.0) 124 (73.4)
86 (86.9) 4 (13.1)
34 (39.5) 2 (50.0)
52 (60.5) 2 (50.0)
106 (80.9) 25 (19.1)
25 (23.6) 10 (40.0)
81 (76.4) 15 (60.0)
0.359
0.112
0.026
0.252
0.038
0.002
0.007
0.002
0.676
0.095
tant issue. Stents are associated with various urinary tract symptoms, including flank pain/discomfort, urinary frequency and dysuria.1– 4 Since they may contribute to patient morbidity, it is important to evaluate their role as part of ureteroscopic procedures. Joshi et reported that urinary symptoms and pain associated with indwelling ureteral stents interfere with daily activity and result in decreased quality of life in up to 80% of patients.1 Lee et al examined morbidity associated with different models/types of ureteral stents and found significant differences in the rate of urinary symptoms associated with stents from different manufacturers.2 In a study by Auge et al 10% of urologists with more than 10 years of experience performed prestenting more than 50% of the time, 2% with at least 2 to 10 years of experience performed pre-stenting
and 0% with fewer than 2 years of experience performed pre-stenting.10 In 1990 Jones et al first reported that a preexisting stent was associated with improved success.11 They noted that inserting a ureteral stent after an unsuccessful attempt to remove a ureteral calculus by ureteroscopy relieved obstruction and increased the likelihood of extraction at a second attempt. In 2005 Hubert and Palmer corroborated this initial finding in 26 pediatric patients.5 In 2007 Rubenstein et al observed a significant increase in SFR in cases of pre-stenting.9 To our knowledge it remains unknown whether the duration of preoperative stenting, a specific stent manufacturer or model, or stent diameter significantly impacts the results of ureteropyeloscopic stone treatment. Minimal indwelling time in our cohort was 14 days. We used stents from only 1 manufacturer that were 6.0Fr to 8.5Fr in diameter. We
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Table 2. Age and clinical characteristics by surgery outcome Characteristic
Total No. (%)
Not Stone-Free
Stone-Free
p Value
Mean ⫾ SD age Mean ⫾ SD stone burden (cm) No. gender (%): M F No. side (%): Rt Lt No. stones (%): 1 2 3 4 or Greater No. preop stent (%): Yes No No. flexible scope (%): Yes No No. UAS (%): Yes No No. scope type (%): Flexible Semirigid Flexible ⫹ semirigid No. semirigid scope (%): Yes No
50.6 ⫾ 13.2 1.3 ⫾ 0.8
3.1 ⫾ 13.0 2.1 ⫾ 1.0
50.3 ⫾ 13.3 1.1 ⫾ 0.7
0.290 (equal variance 2-sample t test) ⬍0.001 (Mann-Whitney U test) 0.757
145 (65.6) 76 (34.4)
19 (13.1) 10 (13.2)
126 (86.9) 66 (86.8)
96 (43.4) 125 (56.6)
15 (15.6) 14 (11.2)
81 (84.4) 111 (88.8)
145 (65.6) 27 (12.2) 26 (11.8) 23 (10.4)
11 (7.6) 3 (11.1) 6 (23.1) 9 (39.1)
134 (92.4) 24 (88.9) 20 (76.9) 14 (60.9)
150 (67.9) 71 (32.1)
17 (11.3) 12 (16.9)
133 (88.7) 59 (83.1)
131 (59.3) 90 (40.7)
25 (19.1) 4 (4.4)
106 (80.9) 86 (95.6)
111 (50.2) 110 (49.8)
20 (18.0) 9 (8.2)
91 (82.0) 101 (91.8)
131 (59.3) 52 (23.5) 38 (17.2)
25 (19.1) 3 (5.8) 1 (2.6)
106 (80.9) 49 (94.2) 37 (97.4)
52 (23.5) 169 (76.5)
3 (5.8) 26 (15.4)
49 (94.2) 143 (84.6)
0.890
⬍0.001
0.252
0.002
0.030
0.006
0.105
also treated patients from elsewhere who at times were noted to have stents made by other manufacturers. However, more often ureteroscopy studies do not indicate the presence of a preexisting stent or assess the impact on surgical outcome and SFR. Hollenbeck et al investigated the outcome of ureteroscopy for ureteral calculi above and below the pelvic brim, and mentioned that patients with stents in place Table 3. Separate and multiple logistic regression models for success Independent Variable Primary stone size (1 cm) Stone burden (1 cm) No. stones Stone 1 coded site: 1 2 3 4 5 Preop stent Stone burden (1 cm) No. stones Preop stent
OR (95% CI) Separate 0.49 (0.29, 0.81) 0.30 (0.19, 0.47) 0.50 (0.36, 0.70) Referent 0.76 (0.22, 2.64) 0.44 (0.11, 1.80) 0.36 (0.11, 1.20) 0.41 (0.11, 1.46) 1.59 (0.72, 3.54) Multiple 0.34 (0.21, 0.55) 0.61 (0.42, 0.89) 2.22 (0.88, 5.63)
p Value 0.006 ⬍0.001 ⬍0.001
0.666 0.252 0.096 0.168
⬍0.001 0.011 0.093
preoperatively were less likely to require dilation.12 The statistical significance of this finding was not stated. Perlmutter et al examined stone location vs the success rate of endoscopic lithotripsy for nephrolithiasis and suggested that preoperatively placed stents passively dilated the ureter, allowing a higher success rate.13 However, this also was not evaluated for statistical significance. Fabrizio et al retrospectively evaluated patients who underwent ureteroscopic management for intrarenal calculi.14 They stated that preoperatively placed stents dilated the ureter but did not comment on any further impact on stone clearance. A number of parameters may influence the success of ureteropyeloscopic stone treatment and preexistent stents should be considered. In our series success rates were high and on comprehensive analysis stone number and cumulative stone burden were negatively associated with success. The small number of total failures may account for this result not being statistically significant. In regard to stone site the odds of failure were highest for lower pole stones. This finding is consistent with the previously published literature.15–18 Treatment failure for lower pole stones is attributable to failure of fragments to clear from this site and difficulty associated with retrograde uretero-
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Table 4. Studies of ureteroscopic treatment for urinary lithiasis and preoperative stents Fabrizio et al14
Hollenbeck et al12
Perlmutter et al13
Rubenstein et al9
No. pts/No. preop stent (%) Present analysis
100/37 (37) No
195/70 (35.9) No
84/37 (44.0) No
Stone site (% success)
Intrarenal (77), ureteral (unspecified) 89 (1)
PU (78), DU (96)
Upper (100), mid (95.8) ⫹ lower (90.9) poles 94.2 (1)
90/36 (69.0) Significantly improved SFR, unspecified confounders Renal, ureteral (each unspecified) 54–78
Median 6.67 mm
Unspecified
Unspecified 39 (46.4) No stone on postop imaging
1–3 or Greater 70 (77.8) No stone on postop imaging
Unenhanced computerized tomography, physiological, factor analysis, renal ultrasound, retrograde pyelography
Computerized tomography, excretory urography
% Overall success (procedure No.) Cumulative stone burden No. stones No. UAS (%) Success criteria
Postop imaging
Unspecified 1–4 or Greater Unspecified 1 or Fewer residual stone fragment 3 mm or less on postop imaging Plain x-ray/ultrasound of abdomen
78–96 (1), 88–99 (2) Mean PU 59.2 ⫹ DU 39.2 mm2 Single or multiple Unspecified No stone on postop imaging
Plain x-ray, computerized tomography, excretory urography
scopic access, which are secondary to anatomical location.19 UASs have been suggested to enhance ureteropyeloscopic stone treatment. However, in our study when they were analyzed with a number of other parameters, they were not significantly associated with higher success. A possible reason is that at our institution we often use a UAS in cases with a large stone burden. If a UAS were used in all cases, this may have produced a different result for this part of the analysis. There are inherent limitations to this study. This is a retrospective study and as such did not minimize confounding or bias, as may be done when performing a prospective, randomized study. Nonetheless, this we considered a large number of parameters that may influence the re-
sults of ureteropyeloscopic stone treatment. Retrograde ureteropyeloscopy for urinary stone disease is also associated with high success rates, which was the case in our cohort. The small size of the failure group may also have limited statistical analysis.
CONCLUSIONS Our results show that ureteropyeloscopic lithotripsy and stone extraction may be performed with high success rates. Routine stenting is not needed before all ureteroscopic procedures for urinary stone disease. Success was significantly inversely related to cumulative stone burden and stone number. Success was also positively related to a preexisting ureteral stent but not significantly so.
REFERENCES 1. Joshi HB, Stainthorpe A, MacDonagh RP et al: Indwelling ureteral stents: evaluation of symptoms, quality of life and utility. J Urol 2003; 169: 1065. 2. Lee C, Kuskowski M, Premoli J et al: Randomized evaluation of ureteral stents using a validated symptom questionnaire. J Endourol 2005; 19: 990. 3. Joshi HB, Newns N, Stainthorpe A et al: Ureteral stent symptom questionnaire: development and validation of a multidimensional quality of life measure. J Urol 2003; 169: 1060. 4. Joshi HB, Stainthorpe A, Keeley FX Jr et al: Indwelling ureteral stents: Evaluation of quality
of life to aid outcome analysis. J Endourol 2001; 15: 151. 5. Hubert KC and Palmer JS: Passive dilation by ureteral stenting before ureteroscopy: eliminating the need for active dilation. J Urol 2005; 174: 1079. 6. Portis AJ, Rygall R, Holtz C et al: Ureteroscopic laser lithotripsy for upper urinary tract calculi with active fragment extraction and computerized tomography followup. J Urol 2006; 175: 2129. 7. Nabi G, Downey P, Keeley F et al: Extracorporeal shock wave lithotripsy (ESWL) versus ureteroscopic management for ureteric calculi (review). Cochrane Database Syst Rev 2007; CD006029.
8. Kranbeck A, Murat F, Getman M et al: The evolution of ureteroscopy: a modern singleinstitution series. Mayo Clinic Proc 2006; 4: 468. 9. Rubenstein RA, Zhao LC, Loeb S et al: Prestenting improves ureteroscopic stone-free rates. J Endourol 2007; 21: 1277. 10. Auge BK, Sarvis JA, L’Esperance JO et al: Practice patterns of ureteral stenting after routine ureteroscopic stone surgery: a survey of practice urologists. J Endourol 2007; 21: 1287. 11. Jones BJ, Ryan PC, Lyons O et al: Use of the double pigtail stent in stone retrieval following unsuccessful ureteroscopy. Br J Urol 1990; 66: 254.
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12. Hollenbeck BK, Schuster TG, Faerber GJ et al: Comparison of outcomes of ureteroscopy for ureteral calculi located above and below the pelvic brim. Urology 2001; 68: 351.
15. Kourambas J, Delvecchio FC, Munver R et al: Nitinol stone retrieval-assisted ureteroscopic management of lower pole renal calculi. Urology 2000; 56: 935.
13. Perlmutter AE, Talug C, Tarry WF et al: Impact of stone location on success rates of endoscopic lithotripsy for nephrolithiasis. J Urol 2007; 71: 214.
16. Grasso M and Ficazolla M: Retrograde ureteropyeloscopy for lower pole caliceal calculi. J Urol 1999; 162: 1904.
14. Fabrizio MD, Behari A and Bagley DH: Ureteroscopic management of intrarenal calculi. J Urol 1998; 159: 1139.
17. Schuster TG, Hollenbeck BK, Faerber GJ et al: Ureteroscopic treatment of lower pole calculi: comparison of lithotripsy in situ and after displacement. J Urol 2002; 168: 43.
18. Elashry OM, DiMeglio RB, Nakada SY et al: Intracorporeal electrohydraulic lithotripsy of ureteral and renal calculi using small caliber (1.9F) electrohydraulic lithotripsy probes. J Urol 1996; 156: 1581.
19. Pearle MS, Lingeman JE, Leveilee R et al: Prospective, randomized trial comparing shock wave lithotripsy and ureteroscopy for lower pole caliceal calculi 1cm or less. J Urol 2005; 173: 2005.
Abbreviations and Acronyms DU ⫽ distal ureter PU ⫽ proximal ureter SFR ⫽ stone-free rate SWL ⫽ shock wave lithotripsy UAS ⫽ ureteral access sheath Submitted for publication April 6, 2009. Study received institutional review board approval. * Correspondence: Division of Endourology and Laparoscopy, Department of Urology, Miller School of Medicine, University of Miami, Dominion Tower, Suite 509 (M814), Miami, Florida 33136 (telephone: 305-243-7261; FAX: 305-2433381; e-mail: [email protected]). † Financial interest and/or other relationship with Applied Medical.
Purpose: Sparse published data exist on the impact of preexistent ureteral stents on the success of ureteroscopic stone surgery. We investigated the impact of a preexistent ureteral stent in relation to a number of parameters and outcomes of ureteroscopic management for urinary lithiasis. Materials and Methods: We retrospectively evaluated a cohort of patients undergoing ureteroscopy for renal and ureteral calculi. Data were abstracted on stone side, size, number and site, patient demographics, total stone burden, ureteral access sheath use, preoperative ureteral stent, ureteroscope type and outcome. Statistical analysis was done. Results: The success rate of 1 and 2 ureteroscopic procedures was 86.9% and 97.3%, respectively. Primary analysis included data on 221 initial procedures. The single procedure success rate for stone site was 91.9% for the distal ureter, 89.7% for the proximal ureter, 83.3% for the renal pelvis, 80.5% for the lower pole and 82.4% for the interpolar/upper pole. Success was negatively associated with primary stone size (p ⫽ 0.020), total stone number (p ⫽ 0.001) and cumulative stone burden (p ⬍0.001). Stone site was not a predictor of success (p ⫽ 0.394). A preexistent stent was positively associated with success but it was not statistically significant (adjusted OR 2.22; 95% CI 0.88, 5.63; p ⫽ 0.254). Secondary analysis in patients who initially underwent flexible ureteroscopy yielded results consistent with those of primary analysis. Conclusions: Results show that ureteropyeloscopic lithotripsy and stone extraction may be performed with a high success rate. Success was significantly inversely related to stone size, cumulative stone burden and number of stones. Success was positively related to a preexisting ureteral stent but not significantly so. Key Words: ureter, ureteroscopy, stents, urolithiasis, lithotripsy
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URETERAL stents are commonly used with various treatment modalities for urinary lithiasis. Stents are useful to prevent the postoperative colic that may be due to passage of residual stones/debris and transient postoperative edema. However, although these devices are useful for these purposes, they are not free of undesirable effects. Stents are associated with various urinary tract symptoms, including flank
pain/discomfort, urinary frequency and dysuria.1– 4 A large number of studies describe postoperative ureteral stenting. However, there are limited data on the impact on surgical outcome when ureteral stents are present before the ureteroscopic procedure. Stents are often placed in emergent scenarios for acute ureteral obstruction, which may be associated with infection or other
0022-5347/09/1826-2768/0 THE JOURNAL OF UROLOGY® Copyright © 2009 by AMERICAN UROLOGICAL ASSOCIATION
Vol. 182, 2768-2774, December 2009 Printed in U.S.A. DOI:10.1016/j.juro.2009.08.043
URETERAL STENTING AND URETEROSCOPIC TREATMENT FOR URINARY LITHIASIS
conditions that preclude immediate definitive management for a stone. They may also be placed in conjunction with SWL or ureteroscopy. Indwelling ureteral stents that may passively dilate the ureter have been used in pediatric urology patients, who often have small caliber ureters.5 However, the impact of preexistent ureteral stents on success in the general population is not clear. We investigated whether preexistent stents have an impact on SFR after ureteroscopy.
MATERIALS AND METHODS Internal review board approval was obtained at our institution before the study. We reviewed our database of patients who underwent retrograde ureteroscopy for ureteral and renal calculi, as done by 1 surgeon between 2002 and 2007. Patients with solitary as well as multiple renal calculi were included in analysis, as were patients in whom previous extracorporeal SWL failed. Patients treated as part of percutaneous procedures were excluded from study. We abstracted data on stone site, size and number, patient demographics, preexisting ureteral stent, intraoperative UAS use, ureteroscope type and model, number of treatments needed to attain stone-free status and treatment success, defined as stone-free status using radiographic criteria. Stone number was coded according to the number of stones as 1, 2, 3 or multiple (coded as 4) when more than 3 stones were present. In multiple stone cases the 3 largest stones were considered for stone site and burden. The latter was defined as the sum in cm of the size of the 3 largest stones. Stone site was coded as 1—DU and/or ureterovesical junction, 2—PU and/or mid ureter, 3— renal pelvis and/or ureteropelvic junction, 4 —lower pole, and 5—interpolar and/or upper pole. DU defined all stones from the ureterovesical junction to the level of the ureter where it crosses the iliac vessels. Mid ureter and PU defined all ureteral stones in the ureter above the iliac vessels up to but not including the ureteropelvic junction.
Treatment Various ureteroscopes were used for ureteroscopic procedures, including ACMI™ MR6 semirigid ureteroscopes, and AUR7, AUR 9, DUR™-8, DUR8 Elite, Karl Storz™ 11274AA, Flex-X™ and Flex X2™ flexible ureteroscopes. All ureteroscopic procedures were performed with guidewires, including a safety wire. Intact stone retrieval, intracorporeal lithotripsy and UAS use were done at surgeon discretion. Ancillary devices included UASs, laser fibers and stone retrieval baskets. UASs included the Forte® with an inner and outer diameter of 12Fr and 14Fr, the Forte XE with an inner and outer diameter of 12Fr and 15Fr, and the Uropass™ with an inner and outer diameter of 12Fr and 14Fr, respectively. Laser fibers included the Coherent® 200 and 365 , the Dornier® 270 , and the AccuFlex™ 200 and ACMI 270 holmium light guide laser fibers. Laser generators used included the VersaPulse®, the mediLAS® H20 and the VersaPulse PowerSuite™ 20 W
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holmium laser. Also used were 1.9Fr and 2.4Fr ZeroTip™ nitinol stone retrieval baskets. Patients were treated primarily with semirigid or flexible ureteroscopy. In cases of semirigid ureteroscopy when suspicion arose that stone fragments had migrated proximal, a flexible scope was used to investigate this possibility and any migrated fragments were removed. In cases of poor visualization, significant edema or persistent extensive stone burden after extensive lithotripsy and stone extraction at surgeon discretion the ureteroscopic procedure was terminated. Ureteral stents were placed at the end of all ureteroscopic procedures.
Followup All patients were seen within 1 to 6 weeks after treatment. All patients underwent radiographic imaging within 1 to 12 weeks after treatment by stone protocol noncontrast computerized tomography (3 mm cuts) and plain x-ray at 1 of 2 health care institutions. Radiographic success was defined as the absence of any stone material. One mm punctate calcifications occasionally seen in the region of the renal papillae were not considered urinary drainage tract stones.
Statistical Methods Statistical methods used focused mainly on comparing patients with vs without a preoperative stent. These 2 groups were compared for age using the independent sample t test and for stone burden (a variable with a highly skewed distribution) using the Mann-Whitney test. Chisquare analysis was done to assess associations between discrete variables. Simple and multiple logistic regression analyses were used to assess preoperative stents and other variables, combinations thereof and their interactions as predictors of success.
RESULTS A total of 259 ureteroscopies were performed during the study period. To preserve statistical independence 13 patients with bilateral ureteroscopic procedures had only data from 1 side chosen at random included in analysis. The figure shows the clinical outcome in all patients. The success rate after 1 ureteroscopic procedure was 86.9%, which increased to 97.3% after 2 ureteroscopic procedures. Of the 221 patients with success after only 1 ureteroscopic procedure (192), failure after only 1 (4) and a failed first ureteroscopic procedure (25) 150 had a stent preoperatively (see figure). Of the patients 71 had no preexisting stent. Table 1 lists characteristics in these 221 patients and their relationship to preoperative stent status. There were no statistically significant differences between patients with vs without a preoperative stent for age (p ⫽ 0.319), primary stone size (p ⫽ 0.417), stone burden (p ⫽ 0.982), gender (p ⫽ 0.631), surgery side (p ⫽ 0.359), total number of stones (p ⫽ 0.112) or success rate (p ⫽ 0.252). However, primary stone site was significantly associated with a preoperative stent, ranging from 51.6% in patients with the primary
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Success and failure in patients with 1 and 2 procedures with success rate calculated as (192)/(192 ⫹ 4 ⫹ 25) ⫽ 86.9% and (192 ⫹ 23)/ (192 ⫹ 23 ⫹ 4 ⫹ 2) ⫽ 97.3%, respectively.
stone at site 1 to 79.2% in those with the primary stone at site 3 (p ⫽ 0.026). The proportion of patients with a preoperative stent was significantly higher in those who underwent flexible vs semirigid ureteroscopy (73.3% vs 60.0%, p ⫽ 0.038). Table 2 shows bivariate analysis of success rates. Success, defined as stone-free status, was not significantly related to age (p ⫽ 0.290), gender (p ⫽ 0.757) or surgery side (p ⫽ 0.890). Success was not significantly related to primary stone location (p ⫽ 0.394) but the success rate ranged from 80.5% for site 4 to 91.9% for site 1 (table 2). A preexisting stent was positively associated with success but this did not attain statistical significance (with vs without a stent 88.7% vs 83.1%, p ⫽ 0.254). Compared with the 29 failed cases the 192 with a successful outcome had significantly smaller primary stone size (mean ⫾ SD 0.9 ⫾ 0.6 vs 1.3 ⫾ 0.8 cm, p ⫽ 0.004) and a lower stone burden (1.1 ⫾ 0.7 vs 2.1 ⫾ 1.0 cm, p ⬍0.001). Success was significantly inversely related to stone number (p ⬍0.001). The success rates decreased linearly from 92.4% in patients with only 1 stone to 60.9% in those with 4 or more (table 2). A flexible ureteroscope was negatively related to success. The success rate was 80.9% vs 95.6% in those primarily treated with a flexible vs a semirigid ureteroscope (table 2). To assess different covariates as potential predictors of successful ureteroscopy bivariate and multivariate logistic regression analyses were done. Table 3 lists the results of separate regression models with the estimated ORs, and corresponding 95% CIs and p values. Statistically significant predictors of failure (OR ⬍1.00) were primary stone size (p ⫽ 0.006), stone burden (p ⬍0.001) and stone number (p ⬍0.001). A preoperative stent was not signif-
icantly related to success but patients with a stent were 59% more likely to achieve success than patients without a stent (table 3). To account for the interrelationship between potential confounders several multivariate models were considered, of which all included a preoperative stent as a forced variable. Table 3 also shows results of the final model using stepwise logistic regression. Results agree with those of the separate models but after adjusting for stone burden and stone number the odds of success in patients with a preoperative stent increased from 1.59 to 2.2 (table 3). Separate analysis, including bivariate and multivariate analyses, was done in 131 patients who underwent flexible ureteroscopy only. On logistic regression analysis primary stone size (p ⬍0.0001), cumulative stone burden (p ⬍0.0001) and stone number (p ⫽ 0.0009) were again negatively associated with success. These results correlated with the analysis in the entire group.
DISCUSSION Ureterorenoscopy is effective for ureteral and renal calculi, and high success rates have been reported.6 – 8 On a meta-analysis ureteroscopy resulted in a higher SFR than SWL for ureteral calculi.7 A systematic review by Rubenstein et al also showed that ureteroscopic removal of ureteral stones achieves a higher SFR than SWL.9 Although there are numerous studies of ureteroscopic management for urinary calculi, few acknowledge or address preoperatively placed stents and their impact on surgical outcome (table 4). The potential impact of ureteral stenting on ureteroscopic procedures is an impor-
URETERAL STENTING AND URETEROSCOPIC TREATMENT FOR URINARY LITHIASIS
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Table 1. Patient age and clinical characteristics by preoperative stent group Characteristic
Total No. (%)
No Preop Stent
Preop Stent
p Value
Mean ⫾ SD age Mean ⫾ SD stone burden (cm) No. gender (%): M F Side: Rt Lt No. stones (%): 1 2 3 4 or Greater No. stone 1 site (%): 1 2 3 4 5 No. stone-free (%): Yes No No. flexible scope (%): Yes No No. UAS (%): Yes No No. scope type (%): Flexible Semirigid Flexible ⫹ semirigid No. semirigid scope (%): Yes No No. stone-free, no flexible scope (%): Yes No No. stone-free, flexible scope (%): Yes No
50.6 ⫾ 13.2 1.3 ⫾ 0.8
49.3 ⫾ 14.9 1.2 ⫾ 0.7
51.3 ⫾ 12.4 1.3 ⫾ 0.8
0.319 (unequal variance 2-sample t test) 0.982 (Mann-Whitney U test) 0.631
145 (65.6) 76 (34.4)
45 (31.0) 26 (34.2)
100 (69.0) 50 (65.8)
96 (43.4) 125 (56.6)
34 (35.4) 37 (29.6)
62 (64.6) 88 (70.4)
145 (65.6) 27 (12.2) 26 (11.8) 23 (10.4)
52 (35.9) 6 (22.2) 4 (15.4) 9 (39.1)
93 (64.1) 21 (77.8) 22 (84.6) 14 (60.7)
62 (28.1) 58 (26.2) 24 (10.9) 43 (19.5) 34 (15.3)
30 (48.4) 14 (24.1) 5 (20.8) 13 (30.2) 9 (26.5)
32 (51.6) 44 (75.9) 19 (79.2) 30 (69.8) 25 (73.5)
192 (86.9) 29 (13.1)
59 (30.7) 12 (41.4)
133 (69.3) 17 (58.6)
131 (59.3) 90 (40.7)
35 (26.7) 36 (40.0)
96 (73.3) 54 (60.0)
111 (50.2) 110 (49.8)
25 (22.5) 46 (41.8)
86 (77.5) 64 (58.2)
131 (59.3) 52 (23.5) 38 (17.2)
35 (26.7) 26 (50.0) 10 (26.3)
96 (73.3) 26 (50.0) 28 (73.7)
52 (23.5) 169 (76.5)
26 (50.0) 45 (26.6)
26 (50.0) 124 (73.4)
86 (86.9) 4 (13.1)
34 (39.5) 2 (50.0)
52 (60.5) 2 (50.0)
106 (80.9) 25 (19.1)
25 (23.6) 10 (40.0)
81 (76.4) 15 (60.0)
0.359
0.112
0.026
0.252
0.038
0.002
0.007
0.002
0.676
0.095
tant issue. Stents are associated with various urinary tract symptoms, including flank pain/discomfort, urinary frequency and dysuria.1– 4 Since they may contribute to patient morbidity, it is important to evaluate their role as part of ureteroscopic procedures. Joshi et reported that urinary symptoms and pain associated with indwelling ureteral stents interfere with daily activity and result in decreased quality of life in up to 80% of patients.1 Lee et al examined morbidity associated with different models/types of ureteral stents and found significant differences in the rate of urinary symptoms associated with stents from different manufacturers.2 In a study by Auge et al 10% of urologists with more than 10 years of experience performed prestenting more than 50% of the time, 2% with at least 2 to 10 years of experience performed pre-stenting
and 0% with fewer than 2 years of experience performed pre-stenting.10 In 1990 Jones et al first reported that a preexisting stent was associated with improved success.11 They noted that inserting a ureteral stent after an unsuccessful attempt to remove a ureteral calculus by ureteroscopy relieved obstruction and increased the likelihood of extraction at a second attempt. In 2005 Hubert and Palmer corroborated this initial finding in 26 pediatric patients.5 In 2007 Rubenstein et al observed a significant increase in SFR in cases of pre-stenting.9 To our knowledge it remains unknown whether the duration of preoperative stenting, a specific stent manufacturer or model, or stent diameter significantly impacts the results of ureteropyeloscopic stone treatment. Minimal indwelling time in our cohort was 14 days. We used stents from only 1 manufacturer that were 6.0Fr to 8.5Fr in diameter. We
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URETERAL STENTING AND URETEROSCOPIC TREATMENT FOR URINARY LITHIASIS
Table 2. Age and clinical characteristics by surgery outcome Characteristic
Total No. (%)
Not Stone-Free
Stone-Free
p Value
Mean ⫾ SD age Mean ⫾ SD stone burden (cm) No. gender (%): M F No. side (%): Rt Lt No. stones (%): 1 2 3 4 or Greater No. preop stent (%): Yes No No. flexible scope (%): Yes No No. UAS (%): Yes No No. scope type (%): Flexible Semirigid Flexible ⫹ semirigid No. semirigid scope (%): Yes No
50.6 ⫾ 13.2 1.3 ⫾ 0.8
3.1 ⫾ 13.0 2.1 ⫾ 1.0
50.3 ⫾ 13.3 1.1 ⫾ 0.7
0.290 (equal variance 2-sample t test) ⬍0.001 (Mann-Whitney U test) 0.757
145 (65.6) 76 (34.4)
19 (13.1) 10 (13.2)
126 (86.9) 66 (86.8)
96 (43.4) 125 (56.6)
15 (15.6) 14 (11.2)
81 (84.4) 111 (88.8)
145 (65.6) 27 (12.2) 26 (11.8) 23 (10.4)
11 (7.6) 3 (11.1) 6 (23.1) 9 (39.1)
134 (92.4) 24 (88.9) 20 (76.9) 14 (60.9)
150 (67.9) 71 (32.1)
17 (11.3) 12 (16.9)
133 (88.7) 59 (83.1)
131 (59.3) 90 (40.7)
25 (19.1) 4 (4.4)
106 (80.9) 86 (95.6)
111 (50.2) 110 (49.8)
20 (18.0) 9 (8.2)
91 (82.0) 101 (91.8)
131 (59.3) 52 (23.5) 38 (17.2)
25 (19.1) 3 (5.8) 1 (2.6)
106 (80.9) 49 (94.2) 37 (97.4)
52 (23.5) 169 (76.5)
3 (5.8) 26 (15.4)
49 (94.2) 143 (84.6)
0.890
⬍0.001
0.252
0.002
0.030
0.006
0.105
also treated patients from elsewhere who at times were noted to have stents made by other manufacturers. However, more often ureteroscopy studies do not indicate the presence of a preexisting stent or assess the impact on surgical outcome and SFR. Hollenbeck et al investigated the outcome of ureteroscopy for ureteral calculi above and below the pelvic brim, and mentioned that patients with stents in place Table 3. Separate and multiple logistic regression models for success Independent Variable Primary stone size (1 cm) Stone burden (1 cm) No. stones Stone 1 coded site: 1 2 3 4 5 Preop stent Stone burden (1 cm) No. stones Preop stent
OR (95% CI) Separate 0.49 (0.29, 0.81) 0.30 (0.19, 0.47) 0.50 (0.36, 0.70) Referent 0.76 (0.22, 2.64) 0.44 (0.11, 1.80) 0.36 (0.11, 1.20) 0.41 (0.11, 1.46) 1.59 (0.72, 3.54) Multiple 0.34 (0.21, 0.55) 0.61 (0.42, 0.89) 2.22 (0.88, 5.63)
p Value 0.006 ⬍0.001 ⬍0.001
0.666 0.252 0.096 0.168
⬍0.001 0.011 0.093
preoperatively were less likely to require dilation.12 The statistical significance of this finding was not stated. Perlmutter et al examined stone location vs the success rate of endoscopic lithotripsy for nephrolithiasis and suggested that preoperatively placed stents passively dilated the ureter, allowing a higher success rate.13 However, this also was not evaluated for statistical significance. Fabrizio et al retrospectively evaluated patients who underwent ureteroscopic management for intrarenal calculi.14 They stated that preoperatively placed stents dilated the ureter but did not comment on any further impact on stone clearance. A number of parameters may influence the success of ureteropyeloscopic stone treatment and preexistent stents should be considered. In our series success rates were high and on comprehensive analysis stone number and cumulative stone burden were negatively associated with success. The small number of total failures may account for this result not being statistically significant. In regard to stone site the odds of failure were highest for lower pole stones. This finding is consistent with the previously published literature.15–18 Treatment failure for lower pole stones is attributable to failure of fragments to clear from this site and difficulty associated with retrograde uretero-
URETERAL STENTING AND URETEROSCOPIC TREATMENT FOR URINARY LITHIASIS
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Table 4. Studies of ureteroscopic treatment for urinary lithiasis and preoperative stents Fabrizio et al14
Hollenbeck et al12
Perlmutter et al13
Rubenstein et al9
No. pts/No. preop stent (%) Present analysis
100/37 (37) No
195/70 (35.9) No
84/37 (44.0) No
Stone site (% success)
Intrarenal (77), ureteral (unspecified) 89 (1)
PU (78), DU (96)
Upper (100), mid (95.8) ⫹ lower (90.9) poles 94.2 (1)
90/36 (69.0) Significantly improved SFR, unspecified confounders Renal, ureteral (each unspecified) 54–78
Median 6.67 mm
Unspecified
Unspecified 39 (46.4) No stone on postop imaging
1–3 or Greater 70 (77.8) No stone on postop imaging
Unenhanced computerized tomography, physiological, factor analysis, renal ultrasound, retrograde pyelography
Computerized tomography, excretory urography
% Overall success (procedure No.) Cumulative stone burden No. stones No. UAS (%) Success criteria
Postop imaging
Unspecified 1–4 or Greater Unspecified 1 or Fewer residual stone fragment 3 mm or less on postop imaging Plain x-ray/ultrasound of abdomen
78–96 (1), 88–99 (2) Mean PU 59.2 ⫹ DU 39.2 mm2 Single or multiple Unspecified No stone on postop imaging
Plain x-ray, computerized tomography, excretory urography
scopic access, which are secondary to anatomical location.19 UASs have been suggested to enhance ureteropyeloscopic stone treatment. However, in our study when they were analyzed with a number of other parameters, they were not significantly associated with higher success. A possible reason is that at our institution we often use a UAS in cases with a large stone burden. If a UAS were used in all cases, this may have produced a different result for this part of the analysis. There are inherent limitations to this study. This is a retrospective study and as such did not minimize confounding or bias, as may be done when performing a prospective, randomized study. Nonetheless, this we considered a large number of parameters that may influence the re-
sults of ureteropyeloscopic stone treatment. Retrograde ureteropyeloscopy for urinary stone disease is also associated with high success rates, which was the case in our cohort. The small size of the failure group may also have limited statistical analysis.
CONCLUSIONS Our results show that ureteropyeloscopic lithotripsy and stone extraction may be performed with high success rates. Routine stenting is not needed before all ureteroscopic procedures for urinary stone disease. Success was significantly inversely related to cumulative stone burden and stone number. Success was also positively related to a preexisting ureteral stent but not significantly so.
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8. Kranbeck A, Murat F, Getman M et al: The evolution of ureteroscopy: a modern singleinstitution series. Mayo Clinic Proc 2006; 4: 468. 9. Rubenstein RA, Zhao LC, Loeb S et al: Prestenting improves ureteroscopic stone-free rates. J Endourol 2007; 21: 1277. 10. Auge BK, Sarvis JA, L’Esperance JO et al: Practice patterns of ureteral stenting after routine ureteroscopic stone surgery: a survey of practice urologists. J Endourol 2007; 21: 1287. 11. Jones BJ, Ryan PC, Lyons O et al: Use of the double pigtail stent in stone retrieval following unsuccessful ureteroscopy. Br J Urol 1990; 66: 254.
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