Ureteral Calculi

Ureteroscopy can be utilized for stones in any location in the ureter. The 2016 AUA Surgical Management of Stones Guideline [3] reported higher overall stone-free rates (SFR) for URS compared to SWL for treatment of patients with ureteral stones (median SFR 90% for URS versus 72% for SWL, RR SWL/URS 0.294, 95% CI 0.214–0.404, p < 0.001). Although URS SFRs increased the more distally in the ureter the stone is located, SWL SFRs did not show location-dependence. Size-stratified outcomes demonstrated that for ≤10 mm ureteral stones, URS SFRs were superior to SWL SFRs at all locations in the ureter (85% versus 66.5%, respectively, for proximal; 91% versus 75%, respectively, for middle; and 94% versus 74%, respectively, for distal ureteral stones). On the other hand, while URS SFRs were superior to SWL SFRs in the middle and distal ureter for stones >10 mm in size (82.5% versus 67%, respectively, for middle ureter and 92% versus 71%, respectively, for distal ureter), there was little difference between the two treatment modalities for larger stones in the proximal ureter (79% for URS and 74% for SWL) [3]. A large, prospective, international URS registry from the Clinical Research Office of the Endourological Society (CROES) comprised of 9681 patients with ureteral stones demonstrated similar SFRs of 84.5%, 89%, and 94% for stones in the proximal, middle, and distal ureter, respectively [6]. SFRs were lower overall (77%) for patients with stones in multiple ureteral locations.

The recommendation of one treatment modality over another for management of patients with ureteral stones depends not only on SFRs but also complication rates. Analysis by the AUA Guideline Panel [3] revealed no significant differences in complication rates between URS and SWL with regard to urinary tract infection (UTI), sepsis, or ureteral stricture, but URS was associated with a higher rate of ureteral perforation than SWL (3.2% versus 0%, respectively). Consequently, the Panel stated that URS is the procedure associated with the highest SFR in a single procedure but that SWL is associated with lower morbidity.

The 2017 EAU Guidelines on Urolithiasis [4] also found higher SFRs up to 4 weeks for URS compared to SWL, although at 3 months the difference was not statistically significant. Likewise, the Panel reported less need for re-treatment and secondary procedures compared to SWL. However, complication rates and need for adjuvant procedures were higher, and hospital stay was longer for URS compared to SWL. Consequently, the EAU recommendation for the management of ureteral stones, which were classified as proximal or distal only, differs slightly from the AUA recommendations. For <10 mm proximal or distal ureteral stones, the EAU Guideline recommends either URS or SWL as first-line therapy. However, for >10 mm ureteral stones, the Panel recommends URS as first-line and SWL as second-line therapy.

It is noteworthy that most of the data on which both Guidelines are based are derived from retrospective studies, with few prospective and/or randomized trials. Furthermore, many of the studies assessing outcomes in patients with proximal ureteral stones were based on semirigid URS. Indeed, among 2656 patients with proximal ureteral stones from the CROES global ureteroscopy study, 72% were treated with semirigid ureteroscopy alone [6]. Although SFRs were not significantly different between semirigid and flexible URS (84% versus 85.5% respectively), failure (3.2% versus 1%, respectively, p < 0.05) and retreatment (14% versus 8%, respectively, p < 0.01) rates were significantly higher with semirigid URS [6]. A recent multicenter, prospective study evaluating outcomes of flexible URS for the management of proximal ureteral calculi (mean stone size 7.4 mm) reported an overall SFR of 95% among 71 patients, although stone clearance was assessed by plain abdominal radiography (KUB) and renal ultrasound (US) at 4–6 weeks rather than the more sensitive computed tomography (CT) [7]. Notably, all ten patients with residual stones had an initial stone size >10 mm. This study further validates the endorsement of flexible URS for the treatment of patients with proximal ureteral stones. Although the CROES study demonstrates that semirigid URS can be successfully used to treat proximal ureteral stones , particularly in woman, the higher failure and retreatment rates with semirigid URS validate the AUA Guideline statement that “clinicians performing URS for proximal ureteral stones should have a flexible ureteroscope available” [3].

Renal Calculi

The indications for treatment of renal calculi are multifold. The EAU Guidelines on Urolithiasis cite the following specific indications for active stone removal: growth of stones, symptomatic stones, stones >15 mm in size, stones <15 mm in size for which observation is not optimal, infection, stones in patients at high risk of stone growth, obstruction, patient preference for treatment, comorbidities, and patient circumstances (occupation, travel) [4]. Acknowledging that the need for treatment of calyceal stones is not well-defined, the EAU Guideline specifically recommends treatment of calyceal calculi that are associated with obstruction, infection, and acute and/or chronic pain.

The AUA Guideline also supports the treatment of patients with symptomatic, non-obstructing, calyceal stones in whom no other etiology of the pain is identified [3]. In addition, the Panel recommends intervention for asymptomatic stones in cases of stone growth, associated infection, and specific situations such as vocational requirements or poor access to medical care [2, 3]. While the AUA Guideline did not specify a stone size threshold for treatment, the EAU Guideline recommends active stone removal for renal stones exceeding 15 mm⁴.

For patients with asymptomatic stones that are not associated with infection or obstruction, the need for intervention is less clear. Natural history studies indicate a cumulative likelihood of developing symptoms or requiring intervention of nearly 50% at 5 years after diagnosis [8–10]. As such, the AUA Panel offers that patients with asymptomatic, non-obstructing calyceal stones may be offered active surveillance [3].

For patients in whom intervention is indicated and/or desired, both the AUA [3] and EAU [4] Guidelines support the use of URS for the treatment of <20 mm non-lower pole renal calculi, although the EAU Panel additionally considers SWL an acceptable first-line therapy for <10 mm stones and percutaneous nephrolithotomy (PCNL) an acceptable first-line therapy for 10–20 mm stones. The AUA Guideline recommends either URS or SWL for <20 mm non-lower pole renal calculi .

For the purpose of treatment recommendations, the lower pole of the kidney is distinguished from non-lower pole locations because of the lower SFRs reported with SWL of lower pole stones compared to other locations. For ≤10 mm lower pole stones, both URS and SWL are considered acceptable first-line treatment options. Indeed, a multicenter, randomized controlled trial (RCT) in which 78 initial patients with ≤10 mm lower pole stones were randomized to SWL or URS found no significant difference in SFRs between the two modalities, despite a 15% difference in SFRs favoring URS (35% for SWL and 50% for URS) [19]. However, for lower pole stones 10–20 mm in size, the AUA Guideline recommend URS but not SWL because of poor SFR for SWL of >10 mm stones [20]. This recommendation is additionally supported by retrospective data from a matched cohort of 99 patients with 1–2 cm lower pole stones who underwent SWL or flexible URS which found significantly higher SFRs by CT imaging (86.5% versus 68%, respectively, p = 0.038) and lower retreatment rate (8% versus 60%, respectively, p < 0.001) for URS than SWL [21].

The development of improved ureteroscopes, small laser fibers, and nitinol baskets resulted in less impact on ureteroscope deflectability, thereby allowing more reliable entry of the ureteroscope into difficult-to-access lower pole locations and successful stone treatment [19]. As such, URS has become a viable treatment option for lower pole stones. Although introduction of a laser fiber can result in loss of 10–15° of deflection of a flexible ureteroscope leading to failure of access into the lower pole [22], repositioning of a lower pole stone to a less dependent calyx can salvage a ureteroscopic procedure and improve SFR. Relocation of 1–2 cm lower pole stones during URS resulted in higher SFRs compared to in situ URS (100% versus 29%, p < 0.001) in one comparative retrospective study [23].

While historically, series of URS for intrarenal calculi demonstrated high SFRs, ranging from 77% to 91% [24–26], these early URS series relied on KUB and/or US to assess stone-free status. More contemporary series utilizing CT have shown substantially lower SFRs, ranging from 50% to 62% [19, 27–29]. The consequences of residual fragments include stone growth, stone passage, or need for surgical intervention. The incidence of a stone-related event attributable to residual fragments has been reported in 20–44% of patients, with need for surgical intervention in up to 29% [30–32]. Although the AUA Guideline does not specify a size threshold above which intervention is recommended for RFs, the Panel did recommend that patients be offered an endoscopic procedure to remove RFs [2]. On the other hand, the EAU Guideline recommends intervention for fragments >5 mm [4]. Neither Guideline takes into account the imaging modality used to determine stone-free status.

The need for retreatment after URS for renal calculi increases with stone size. Karakoyunlu and colleagues [16] performed a single-center RCT comparing PCNL (n = 30) to staged URS (n = 30) for >2 cm renal pelvic stones (mean stone size 27 mm for URS and 26 mm for PCNL). Repeat URS was performed until patients were left with no RF or with RFs ≤ 4 mm. PCNL was performed only once. URS patients underwent a mean of 1.83 sessions per patient (one session in 9 patients, two sessions in 17 patients, and three sessions in 4 patients) and also required a mean of 2 weeks of treatment time to become stone-free. SFR was statistically comparable between the two treatment modalities despite lower SFR for URS (67% for URS and 87% for PCNL, p = 0.067), and therefore the authors concluded that if patients are willing to accept longer overall treatment and operative times and a greater number of procedures , then staged URS is an effective and safe modality.

Bilateral Stones

Bilateral stones occur frequently, and many patients desire same-session bilateral treatment to prevent future stone events. Neither Guideline specifically endorses nonurgent, simultaneous, bilateral treatment of renal calculi, although there are substantial published data addressing bilateral URS. Review of the CROES global URS registry identified 2153 patients treated for multiple renal and/or ureteral calculi, of whom 1880 (87.3%) and 273 (12.7%) underwent unilateral and same-session bilateral URS, respectively [33]. Although there was no significant difference in complication rates between unilateral and bilateral URS groups, univariate analysis demonstrated lower SFRs (OR 0.7, 95% CI 0.49–1.00, p = 0.048), higher re-treatment rates (OR 1.52, 95% CI 1.13–2.05, p = 0.006), and longer operative times (OR 1.41, 95% CI 1.11–1.80, p = 0.005) for same-session bilateral URS compared to unilateral URS.

Ingimarsson and associates [34] identified 113 patients who underwent 117 bilateral same-session URS for renal and/or ureteral calculi. SFR assessed by KUB/US at 6 weeks was 91%. Ureteral injuries occurred in 2.1% of renal units (5/234), of which 3 were superficial (grade I) and 1 each were grade II and grade III, all of which were managed with stent placement for 2 weeks. Short-term complications were largely Clavien-Dindo I–II (n = 15) and the remainder were Clavien-Dindo III (n = 4). At 6 weeks follow-up, no patients demonstrated evidence of stricture, new-onset hydronephrosis , or significant change in creatinine from baseline. Of note, 11% of patients required immediate, unplanned admission after surgery, and another 12% were seen in the emergency department within 30 days of the procedure with pain, fever, or other symptoms. An additional 19% of patients called with stent pain or renal colic post-stent removal. The authors admit these numbers may indicate a higher rate of discomfort after bilateral same-session URS than after unilateral URS. Indeed, in a retrospective study of 1798 patients undergoing URS, Tan and co-workers [35] found on multivariate analysis that bilateral URS was one of the factors associated with a higher likelihood of unplanned admission (OR 2.88, 95% CI 1.19–6.99, p = 0.019).

A number of bilateral same-session ureteroscopy series have been reported [34, 36–41] (Table 2.3). SFRs after one therapeutic session ranged from 52% to 90%. Mild ureteral injuries were not uncommon, and one study [37] with long-term follow-up showed that 4.5% of patients developed ureteral strictures after 6–12 months. Major postoperative complications were uncommon, with most complications classified as Clavien grades I–II. Despite demonstrated safety and efficacy of bilateral same-session URS, however, many surgeons are still reluctant to perform bilateral URS. Rivera and colleagues [42] conducted a survey of 153 members of the Endourological Society querying them on their preferred management of bilateral stone disease. Although a higher proportion of urologists were willing to perform same-session bilateral URS (48%) than bilateral PCNL (38%), still less than half of urologists surveyed indicated that they are comfortable treating stones in both kidneys and ureters in the same setting ureteroscopically.

Table 2.3

Bilateral same-session ureteroscopy for calculi series

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