To identify factors (other than pre-stenting) that were predictive of ureteral injury, we evaluated ureteral injuries caused by the insertion of a 13-Fr ureteral access sheath in non-prestented patients; we had three main findings. First, the rate of ureteral injury (grade ≥ 2) by a 13-Fr ureteral access sheath was 19.3%, which was considerable. Second, most ureteral injuries occurred in the proximal ureter. Third, male sex was a significant predictive factor for ureter injury, according to multiple logistic regression analysis. To our knowledge, there have been no reports concerning the incidence of ureteral injury caused by a 13-Fr ureteral access sheath. Although 13-Fr ureteral access sheaths are not very large in diameter, the risk of ureteral injury should be carefully considered. Furthermore, there have been no reports concerning the locations of ureteral access sheath-related ureteral injuries. Because most ureteral injuries occurred in the proximal ureter in our study, we recommend assessment of the ureteral wall with a flexible ureteroscope at the end of URSL. Particular attention should be given to male patients, and it may be better to use a smaller diameter sheath during URSL in these patients.
Ureteral access sheaths have become popular because of their ability to access the upper lumen and evaluate any part of the kidney, repeatedly and rapidly enter the ureter and collecting system, improve drainage, improve visibility, reduce intrarenal pressure during pulse irrigation, protect the scope, and avoid ureteral lesions during stone fragment removal.7, 8 However, there have been some concerns about ureteral access sheath-related ureteral injuries.6 Additionally, ureteral access sheath-related intraluminal compression of the ureter may compromise ureteral blood flow and cause secondary stricture.8–10 Therefore, Breda et al.11 considered the ureteral access sheath to be safe and useful, although its use is associated with some risks and limiting factors.
Traxer et al.6 prospectively evaluated ureteral injuries by a 14-Fr ureteral access sheath using a new classification system; they found that the rate of high-grade (grade ≥ 2) injury was 13%. Furthermore, they reported that male, older, and non-prestented patients had greater risks of severe ureteral access sheath-related ureteral injuries. In a prospective randomized trial, Loftus et al.4 found the rate of high-grade (grade ≥ 2) injury caused by a 14-Fr ureteral access sheath was 23.9%. Furthermore, they reported that male sex, high stone burden, longer sheath insertion time, and a more difficult subjective rating of sheath placement were associated with high-grade ureteral injuries. In the present study, the rate of high-grade injury was 19.3%. Because pre-stenting was not performed in our patients, whereas it was in the study by Traxer et al.,6 our data was high than the data of Traxer et al. Furthermore, our data was low than the data of Loftus et al.4 Because pre-stented patients were not included in the study by Loftus et al., we presumed that the difference in ureteral access sheath size led to the difference in results between studies (Loftus et al. used 14-Fr access sheaths, whereas we used 13-Fr access sheaths).
Some investigators have described ureteral access sheath-related ureteral injuries and the risk factors for such injuries. Traxer et al.6 reported that the strongest predictor of severe ureteral injury was pre-stenting, whereas Tracy et al.12 reported that use of a large-caliber (14/16-Fr) ureteral access sheath did not increase the risk of ureteral injury in a patient who was pre-stented. Thus, pre-stenting has been presumed to reduce the risk of ureteral access sheath-related ureteral injury.6,12,13 However, several complications have been reported in relation to ureteral stenting, including incomplete emptying, bladder pain, frequency, hematuria, and migration. Additionally, ureteral stenting reportedly diminished urination-related quality of life in 80% of patients who underwent the procedure14. Accordingly, the American Urological Association and European Association of Urology guidelines recommend avoiding routine pre-stenting, although some methods to improve stent-related symptoms have been reported15–17. Thus, there is a need to investigate techniques that can reduce ureteral access sheath-related ureteral injury without pre-stenting. Loftus et al.4 suggested that surgeons should have a low threshold for switching to a smaller sheath when resistance is encountered or if placement time is prolonged. In our multiple logistic regression analysis, we regarded sex, age, body mass index, impacted stone presence, and preoperative urinary infection as potential predictive factors for ureteral injury. Traxer et al. reported that sex and age might be predictive factors for ureteral injury.6 Therefore, we considered body mass index as a potential predictive factor; moreover, the presence of impacted stones and preoperative urinary infection may lead to ureteral wall weakening. Our results showed that male sex was a significant predictive factor for ureteral injury, according to multiple logistic regression analysis. Although this predictive factor has not been previously described, Traxer et al. suspected that ureteral injury is related to differences in sex hormones or to the higher tonic effect of the psoas muscle in male patients.6 Thus, a smaller sheath may be preferable for URSL in male patients. However, the ureteral access sheath size should be carefully selected. The ureteral access sheath size was 14 Fr in the studies by Traxer et al.6 and Loftus et al.,4 whereas it was 13 Fr in our study. Therefore, a smaller sheath (e.g., 12 Fr or 11.5 Fr) may be more appropriate. Notably, Koo et al.18 investigated the efficacy of preoperative α-adrenergic antagonists to reduce the force of ureteral access sheath insertion. They concluded that preoperative α-adrenergic antagonists and slow sheath placement may reduce the maximum force of ureteral access sheath insertion. The technique for ureteral access sheath insertion and the medication used during the procedure may also be important for reducing ureteral injuries during ureteral access sheath insertion.
This study had some limitations. First, it used a retrospective design. Second, long-term outcome data were not available for patients in this study. In future studies, we plan to investigate the relationship between ureteral injury and ureteral stricture. Third, this study used a non-randomized design and included only one comparison group. However, all patients were non-prestented patients who were presumed to require the use of a ureteral access sheath, and all patients underwent insertion of a 13-Fr ureteral access sheath. This approach may have reduced the potential for selection bias.
In conclusion, we evaluated ureteral injuries caused by the insertion of a 13-Fr ureteral access sheath. The rate of ureteral injury (grade ≥ 2) by a 13-Fr ureteral access sheath was 19.3%, and most ureteral injuries occurred in the proximal ureter. Furthermore, male sex was a significant predictive factor for ureteral injury, according to multiple logistic regression analysis. Although we recommend confirmation of a whole ureter, it is important to at least confirm the proximal ureter when using a 13-Fr ureteral access sheath, particularly in male patients.