The incidence of lithangiuria shows an increasing trend, especially the upper urinary tract urolithiasis. In contrast, the incidence of lower urinary tract urolithiasis, especially the bladder calculi, is on a sharp decline . In a recent survey, the prevalence of renal calculus was up to 6.4% in China mainland . To our best knowledge, upper urinary tract urolithiasis has been considered the most common urological diseases, which causes great burden to the public health. To date, ESWL and URS have been frequently utilized for treating upper urinary tract urolithiasis, leading to a SFR of 73%-91% and 93%-98%, respectively . Patients in the ESWL group achieved a 92.70% overall SFR with a 44.88% retreatment rate and an 11.02% auxiliary procedure rate . In this study, the 1-month SFR in the ESWL group and URS group was 75.9% and 88.2%, which was in line with the previous findings . The residual calculi would serve as the infection source, which led to recurrence of calculi . Moreover, the upper urinary tract urolithiasis was triggered by metabolic disorder induced by pathological factors and the potential interaction. After treatment, there would be newly generated calculi in the patients in a SF status. Multiple studies indicated that the 1-year and 3–5 year recurrence rate of urological calculi was 6.7% and 21.3% for the lithangiuria, respectively. The risk of lifelong recurrence was up to 60%-80%. In a previous study, Vaughan et al  indicated that the stone recurrence rate was 3.4% after the first episode, 7.1% after the second episode, 12.1% after the third episode, and 17.6% after the fourth or higher episode. Therefore, despite the fact that the standard for the outcome evaluation of residual fragments in the upper urinary tract was relied on the no residual stones after treatment [11, 12], some patients may present post-treatment recurrence, which showed increase in time with the disease duration and treatment frequencies . On this basis, long-term prevention and treatment is necessary for these patients.
To date, the regimens based on drugs and nutrition interference for the simultaneous release of stones from the upper urinary tract have been considered the most safe and economic ways . However, the stone release method based on drugs is not recommended for the long-term usage as many patients show poor treatment compliance . The metabolic disorder induced stone formation was associated with intermittent rather than persistent factors that may affect the efficiency of nutrition and diet interference. Meanwhile, the metabolic disorder induced by stone formation showed an intermittent pattern . Furthermore, the simultaneous release possibility of ureteral stones with a diameter of about 2–4 mm was up to 95%, while that of the stones with a diameter of > 5 mm was merely 50%. Therefore, conventional treatment regimen was not effective for the long-term prevention and management of upper urinary tract urolithiasis.
Post-URS stent replacement could prevent ureteric stenosis and obstruction, which could contribute to the recovery of renal function. In the long-term follow-up, the patients presented simultaneous release of stones after stent removal. In this study, the simultaneous release of stones in the URS group was significantly higher than that of the ESWL group. In addition, Logistic regression analysis indicated that stent replacement was an independent risk factor for the simultaneous release of the stones. The risk of auto-release of stones in the URS group showed increase, which were about 3-fold higher than that of the ESWL group. Further analysis indicated that the mean diameter of the stenosis in the ureter passing through the iliac vessels after treatment was up to 6 mm, which showed an increase of 70%-100% compared with before. In the ESWL group, there were no significant differences. In a previous study , about 68% of the urological stones showed a diameter of less than 5 mm. Therefore, dilation of ureter after stent removal contributed to the release of the majority of stones in the upper urinary tract. The treatment efficiency was more effective and convenient compared with the drugs or diet interference based regimens. Meanwhile, the efficiency was not hampered by the patient compliance and metabolic factors mediated by stone formation, which was beneficial to the treatment and long-term prevention of the upper urinary tract urolithiasis. The major features were as follows: (i) It could promote the auto-release of the residual CIRF stones, and attenuate the possibility of recurrence. (ii) There was no obstruction in the urinary tract after ureterectasis, together with decline of crystal deposition and stone recurrence in the urinary tract. (iii) It could correct partial congenital stricture of ureter, and induce decline of the recurrence of the stones. Moreover, based on the calculation of the ureter pressure , the pressure would be decline after ureterectasis, which may be beneficial to the recovery of renal function.
There are some limitations in this study. First, we do not measure the diameter of the ureter in the patients underwent CT scan. Compared with the ultrasonography, CT scan is more accurate and available. Second, the ureteric stenosis near the iliac vessels served as the evaluation standard, however, the pyeloureteral junction stenosis and bladder orifice stenosis were not evaluated. For the reasons, the pyeloureteral junction stenosis showed significant retraction due to severe pyelectasis and treatment-related factors, which could not accurately reflect the changes of the ureter diameter. The bladder orifice stenosis was near or embedded in the bladder, which could not be clearly displayed by ultrasonography or CT scan. Meanwhile, it passed through the iliac vascular stenosis and was localized in the middle of the ureter, which was convenient for the localization and evaluation as it was slightly affected by the pyelectasis.
Currently, the selection of URS or ESWL for treating upper urinary tract stones is mainly relied on the stone size and position , post-treatment SFR , and the complications. The combination of URS and stent replacement contributed to the ureterectasis and the simultaneous release of stones from the upper urinary tract. The method is easy to perform, and was not affected by the life habits and the internal environments. Therefore, it could be used as an evaluation standard for the URS, especially in the patients with obesity and hyperuricemia presenting high risks of recurrence as well as those with repeated recurrence.