Asymptomatic renal stone associated with ipsilateral symptomatic ureteral stone is not a rare event [10,11]. URL has equivalent or superior results comparing with ESWL in treating symptomatic ureteral stone.  When encountering a coexisted ipsilateral asymptomatic renal stone, no established guidelines are available. Active observation, ESWL, PCNL as well as RIRS should be discussed. Previous research had showed that active observation will be associated with a higher risk of surgical intervention [2,3]. Patients choosing ESWL often needed multiple sessions to achieve higher SFR . PCNL, a favoured treatment for stone >2 cm, is associated with higher potential risks, such as bleeding, urosepsis, and urine leakage . Recently, simultaneously RIRS becomes feasible in treating ipsilateral renal stone and seems to be an attractive option. We compare the outcomes of this simultaneous modality to URL alone in this study.
Ureteral stone was completely removed in each group. In simultaneous RIRS group, the overall renal SFR after 1 month was 86.1%, which was similar to that of previous reports. Goldberg H et al. showed that patients with pre-procedural D-J stent can achieve a higher renal SFR (93.3% VS 71%) . However, the difference was not found in this study. Inability to reach the lower pole calyx may be the main reason of RIRS failure [15,16]. We observed that eight cases were due to this. Also, the other predictive factor of renal SFR was stone size. Grasso and Ficazzola reported that RIRS can achieved an SFR of 82%, 71% and 65% with stone size of <1 cm, 1–2 cm and >2 cm, respectively . RIRS may be required to clear a large stone by multiple procedures . In our center, it is often performed for renal stone in size of <2 cm, which can achieved a higher SFR in one session. In this study, the simultaneous RIRS achieved 86.1% renal SFR for treating this size stone.
The other important results were lower ATR, while complications were not significantly increased. The causes of the higher ATR in URL alone group were often stone induced (Table 3). In Streem’s and Glowacki’s study, respectively, Patients with active observation, more than 70% and 48.5% required treatment due to increased stone duration or clinical symptomatic episode in next 5 years [18,19]. Although our mean follow-up period were >18 months, the ATR was 69.4% in URL alone group comparing to only 5.6% in simultaneous RIRS group. Few patients with residual stone may be one of the reasons. And the other reason was that causes of auxiliary treatment after RIRS were unexpected incidents such as complications or flexible ureteroscope damage, which is low in current reports Therefore, it is important to emphasize the possibility of auxiliary treatment in patients with URL alone is up to 70%, and with simultaneous RIRS is only required in unpredictable situation during preoperative conversation.
UAS is becoming increasingly popular worldwide because of facilitating the access, decreasing intrarenal pressure and protecting the scope . However, several studies had shown that the over distention created by UAS may induce ureteral ischemia and wall injuries . In this study, we found that ureteral perforations were developed in two patients in simultaneous RIRS group, who were not pre-stented. Traxer O and Thomas A reported that D-J prestenting significantly decreases the incidence of severe access sheath related injuries . Moreover, overall complications were significantly less in patients with pre-procedural D-J stent (6/50 vs 10/22, P = 0.04). Thereby, it is wisdom to place DJ stent pre-procedurally in patients who were planned to undergo simultaneous RIRS.
Although RIRS had minimal invasive nature, the low morbidity was probably due to greater expertise in high-volume RIRS center. When a surgeon is still in his learning curve of RIRS, more attention should be paid in performing simultaneous modality.
Beside the invasive nature of RIRS, another disadvantage included the consumption of expensive instruments such as fragile flexible ureteroscope, nitinol basket and UAS. Large studies showed the need for repair flexible ureteroscope after an average of 18 cases . Obviously, the costs for RIRS are higher than URL. In our study, although mean procedure per patient was significantly more in URL alone group, the mean medical cost per patient was still higher in simultaneous RIRS group during follow-up (mean >18 months). Simultaneous modality does not appear to be cost effective. However, SH Lee et al. reported that patients benefited from cost-effectiveness when choosing RIRS simultaneously, with respect to their health insurance system . Rencently, repair for a new generation flexible ureteroscopes was needed after 20–22 procedures [25,26]. Moreover, flexible ureteroscopes can have a significantly longer lifespan (10.6 vs 21.6 uses before damage), by following guidelines and with training. . Thus, we believed that the results may be changed with the developments of instruments, techniques and national health insurance system.
An interesting observation from study was that 47.8% patients in URL alone group underwent ESWL. Despite higher retreatment rates, it remains a preferred option because of non-invasive nature and high level of acceptance by patients and doctors. Although Keeley FX et al. demonstrated that ESWL for small asymptomatic renal stones does not offer any advantage to patients in terms of SFR comparing to observation (28% vs 17%, P = 0.06) , we found it can partly eliminate apprehensiveness of patients, and can achieve a higher SFR in upper pole renal stone. However, A policy of treating asymptomatic renal stones with ESWL may be still associated with a high risk of requiring invasive procedures > 50% patients were required additional URL, RIRS or even PCNL for obstructing steinstrasse and residual stone.
The main limitation of this study is its retrospective design. Allocation to a treatment modality depended on the surgeon’s preference. We tried to overcome this possible selection bias by comparing match groups of patients and stones. Another limitation was the small number of patients and a single center study. Therefore, a prospective randomized controlled study with a larger sample of multiple centers with a long time follow-up is needed.