Introduction
Urolithiasis (ureteral calculi) is a common urological complication and public health problem that frequently leads to renal colic and eventually obstructive uropathy. Urolithiasis has a prevalence of 13% in men and 7% in women which is dependent on geographical area, age, and sex; its peak incidence is estimated to be at the third to fourth decades of life (1).
Socioeconomic status, environmental factors, genetic predisposition, and certain metabolic disorders are the possible risk factors of this renal condition.
Its occurrence rate is increasing in children which is associated with high morbidity rate and serious consequences to patient’s quality of life that might be due to the relapse of the disease (2).
Colic pain due to stone movement and irritation of submucosal nerve fibers, dark or bloody urine, painful urination, nausea, vomiting, and fever are the most common signs of urolithiasis.
Stones usually form in renal collecting system and store in ureteropelvic junction, over the iliac vessels, and at the ureteric meatus. Various treating strategies are used for ureteric stones based on stone size, symptom severity, degree of obstruction, kidney function, stone location, and urinary tract infection status including observational to surgical methods.
Almost, 98% of all ureteral calculi ESWL is a non-invasive method which is more accepted, does not need general anesthesia, and it can be performed in out-patients facilities. During the ESWL, high-energy sound waves (shockwaves) are passed through body via outside sources to break the stones that they can easily move through urinary tract and outside the body. In this strategy, no instrument will be needed to be placed through the skin.
Ureteroscope will be placed into the affected ureter through the urethra and bladder. In this technique, stones will be broken into smaller pieces using laser fiber or lithoclast probe; thus, small stones can pass out spontaneously. Therefore, it is important to reveal that which modality has benefits over another technique in the management of ureteric stones. In this regard, we decided to review the existed publications assessing the efficacy of each method in the treatment of urolithiasis to evaluate the advantages of one method over another.

Methods
We performed a systematic review to compare the benefits and complications following ESWL and URSL for the treatment of urolithiasis. PubMed was searched to obtain all the English language articles relevant to the scope of this review. Search strategy consisted of the following terms: ureteroscopy AND extracorporeal shockwave lithotripsy AND ureteral calculi AND ureteral stones. Reference list of the excluded studies were also searched for any additional article. Inclusion criteria were any randomized control trial which studied the treatment of ESWL or URSL in adult patients with ureteral disease confirmed by imaging. Results of the stone-free rate and retreatment rate were extracted from each article and both have been proposed as the odds ratio of ESWL compared with URSL. Odds ratio higher than 1 means that the URSL group has lower possibility to experience the event (stone-free rate and retreatment rate). Odds ratio lower than 1 means that URSL group is more likely to experience the event.

Results
Based on the mentioned search strategy, a total of 616 articles were extracted primarily. Reviews, case reports, retrospective and prospective studies with no randomization were excluded after studying the title, abstract, and eventually the full text of the retrieved articles. All the included RCTs were published in English from 1999 to 2015.
 Finally, we obtained 11 articles as the most relevant publications. Baseline characteristics and outcomes of these studies are summarized in Table 1. Overall, 1663 patients were considered in this systematic review which were under the ESWL treatment or URSL. The sample size was 30 as the minimum and 390 as the maximum in the included studies. The majority of enrolled patients were male.
Total of five included RCTs were about small proximal ureteric calculi, and other six articles were about distal ureteric stones. Patients were almost at similar ages within studies. Most of the studies performed ESWL by applying intravenous sedation, and only one study performed by Peschel, in 1999, used general anesthesia for conducting this modality (9).
Stone-free rate
Among studies performed on proximal and distal ureteric stones, calculated odds ratio showed that the event of stone-free rate was possibility higher in patients under URSL compared with those under ESWL.

Retreatment rate
The calculated odds ratio of event of retreatment rate showed that ESWL method in patients with proximal ureteric stones was likely associated with higher retreatment rate while compared with URSL method.

Operation time
This outcome was almost longer in groups of patients with proximal or distal ureteral stones under the method of URSL compared with ESWL.

Discussion
ESWL and URSL are the most prevalent therapeutic methods in the treatment of ureteric stones. The advantages of one modality over another in the treatment of proximal and distal ureteric stones are still under debate. Thus, this systematic review aimed to evaluate the efficacy of each method on stone-free rate, retreatment rate, and operation time through previous RCTs.
Obtained odds ratio for patients with proximal and distal ureteral stones were lower than 1 regarding the stone-free rate in each study, which indicate that URSL is favored over ESWL regarding this event. However, odds ratio higher than 1 for the retreatment rate shows higher possibility of retreatment rate during ESWL modality which eventually proposes URSL as a favorable method for reducing the incidence of this event. Retreatment is defined as subsequent intervention similar to the initial intervention used for the disease condition. Therefore, URSL was a more invasive modality compared to the method of ESWL; and according to the included studies on patients with proximal and distal ureteric stone disease, URSL method revealed better efficacy on stone-free rate, but lower benefits regarding retreatment rate compared with ESWL. These two methods were also compared regarding the operation time which revealed longer operation time with URSL compared with ESWL which was due to its higher invasiveness. No principal complication was reported following any of these modalities. Although ESWL might be associated with lower stone-free rate and higher retreatment possibility, in some studies, ESWL was proposed as the preferred method due to lower subsequent complications and no general anesthesia requirement (15,16). However in some other studies, surgeon expertise during the URSL modality was proposed as an influential factor which could reduce the subsequent complications (17,18). In one meta-analysis, URSL modality was also reported to be associated with longer hospital stay and postoperative complications compared with ESWL. Technological improvements of small diameter semirigid and flexible ureteroscopes has resulted in increased progression in the treatment of ureteral stones and lower complications. These developments have demonstrated the ureteroscopy with lithoclast as an acceptable and first line therapeutic modality in the treatment of large proximal ureteral stones (19). Stone size is also an important factor which could affect the stone-free rate, thus it is suggested to be estimated before the operation. Plain x-ray of kidney-ureter-bladder (KUB) and computed tomography with coronal reconstruction are proposed as routine strategies for the determination of the ureteric stone size preoperatively (20,21). One study also reported the negative effect of high body mass index (greater than 30 kg/m2) on ESWL outcome.

Conclusion
In the treatment of proximal and distal stones, URSL has been a favorable procedure due to higher stone-free rate and lower retreatment rate compared to the ESWL. However URSL is more invasive and is associated with longer operation time. Moreover, it is concluded that the high heterogeneity of some influential factors in evaluated studies including the study design, stone location, types of ureteroscope, intracorporeal lithotripsy devices, time to follow-up, and surgeon experience might affect the choice of an appropriate operation type.

Acknowledgement
We would like to thank Clinical Research Development Unit of Ghaem Hospital for their assistant in this manuscript.

Conflict of Interest
The authors declare no conflict of interest.