FACTORS PREDICTING PRE-STENTING IN UNCOMPLICATED URETEROSCOPY FOR PEDIATRIC UROLITHIASIS
Michelle K. Arevalo, MS31, Shuvro De, MD1, Jennifer Tracy, PPCNP2, Lai Jiang, MS41, Sheena Pillai, MS21, Bruce J. Schlomer, MD2, Linda A. Baker, MD2.
1University of Texas Southwestern Medical Center, Dallas, TX, USA, 2Children's Health Dallas, Dallas, TX, USA.
Background: Upper tract inaccessibility limits performance of ureteroscopic stone extraction under one anesthetic in a significant percentage of children. In such cases, passive ureteral dilatation (pre-stenting) with later ureteroscopic stone extraction is necessary. Previous efforts to investigate the relationship between patient age, gender, BMI and the need to pre-stent yielded no definitive associations, but sample sizes were small. This study sought to examine factors associated with pre-stenting and evaluate for any association between pre-stenting and stone outcomes.
Methods: With IRB approval, all pediatric patients undergoing ureteroscopy for stone management by 7 pediatric urologists from 2009 - 2015 were identified. Children with complex urologic histories/anatomy or comorbid conditions mandating pre-stenting (i.e. UTI) were excluded. Thus this study was limited to uncomplicated attempts at ureteroscopy for urolithiasis in otherwise healthy children. Ureteroscope and/or access sheath passage was attempted in all and decision to pre-stent was made by each individual surgeon. Demographic and stone characteristics were compared in the pre-stented and not pre-stented group. Factors associated with being pre-stented were evaluated with univariable and multivariable logistic regression.
Results: There were 124 ureteroscopy cases included with 11 bilateral cases for a total of 135 ureteroscopies included (Table 1). Overall, 30% of ureters were pre-stented. Pre-stent rates varied by surgeon (0 - 59%) and approached statistical significance on univariable analysis (p = 0.07). On multivariable analysis (Table 2), a 10% higher BMI percentile was associated with 0.8 times the odds of being pre-stented (95% CI: 0.7 - 0.9, p<0.001). Increasing stone size and stone position above the distal ureter/UVJ were associated with increased odds of being pre-stented (OR: 1.2 [1.02 - 1.31], OR: 6.0 [1.3 - 27.9], respectively). Both groups had similar operative times and stone free rate, defined as no stones seen on follow up imaging (typically renal u/s). Pre-stenting did not significantly alter ability to place a ureteral access sheath.
Conclusions: About 30% of children undergoing ureteroscopy are pre-stented at our institution. More proximal stone position, larger stone size, and lower BMI percentile were associated with being pre-stented. Rates of pre-stenting were highly variable by surgeon. Pre-stenting was not associated with improved stone free rates, operative times, or successful placement of a ureteral access sheath; in essence, pre-stenting provided no additional benefit beyond ureteroscope access in this otherwise uncomplicated population. This information can be used to counsel families and we recommend that a pre-stenting in patients without a UTI be performed only after initial attempt at ureteroscopy.
|Table 1: Comparison of pre-stented and not pre-stented groups|
(n = 40)
|Not Pre-stented |
(n = 95)
|Age yrs||12.7 (4.5)||14.2 (3.6)||0.51|
|BMI Percentile||43% (34%)||65% (31%)||0.0041|
|Male||22 (55%)||57 (60%)|
|Female||18 (45%)||43 (40%)|
|White||29 (73%)||55 (58%)|
|Black||2 (5%)||4 (4%)|
|Hispanic||8 (20%)||34 (36%)|
|Other||1 (3%)||2 (2%)|
|Renal||28 (71%)||58 (62%)|
|Proximal Ureter/UPJ||2 (5%)||5 (5%)|
|Mid. Ureter||4 (10%)||5 (5%)|
|Distal Ureter/UVJ||5 (13%)||25 (27%)|
|Stone Size in mm3||6.4 (3.9)||5.4 (3.2)||0.11|
|Operative time (hrs)||1.8 (0.9)||1.8 (0.8)||0.91|
|Access sheath attempted and placed?||27/30 (90%)||53/62 (85%)||0.42|
|Stone free on follow up imaging?3||22/34 (65%)||52/80 (70%)||0.92|
|Continuous data presented as mean (SD), categorical data presented as n(%)|
2Fisher Exact test
32 missing stone size, 3 missing stone location, 21 missing follow up imaging
|Table 2: Multivariable analysis of factors associated with being pre-stented|
|Univariable OR (95% CI)||P-value||Multivariable OR (95% CI)||P-value|
|Age1||0.9 (0.8-1.0)||0.06||0.9 (0.8-1.0)||0.08|
|BMI percentile2||0.8 (0.7-0.9)||0.001||0.8 (0.7-0.9)||<0.001|
|Stone location3||2.5 (0.9-7.1)||0.09||6.0 (1.3-27.9)||0.02|
|Stone size4||1.1 (1.0-1.2)||0.2||1.2 (1.0-1.3)||0.03|
|Surgeon5||3.7 (1.5-9.2)||0.005||12.5 (3.3-47.1)||<0.001|
|1OR for 1 year increase in age|
2OR for 10% increase in BMI percentile
3OR for distal ureter/UVJ vs proximal to distal ureter/UVJ
4OR for 1 mm increase in stone size
5OR for surgeons with >40% pre-stent rate
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