Do Stone Size and Impaction Influence Therapeutic Approach to Proximal Ureteral Stones?

Background/Aim. Primary therapeutic approach to lum-bar ureteral stones is still contraversial. The aim of the study was to investigate the influence of stone impaction and size on the effectiveness of proximal ureteral stone lithotripsy. Methods. A total of 123 patients with proximal ureteral stones were investigated in this prospective study performed in a 10-month period. The patients were divided into the group I – 86 patients treated with extracorporeal shock wave lithotripsy (ESWL) and the group II – 37 patients treated with " Swiss " Lithoclast. In the group I, 49 stones (57%) were classified as impacted, while 20 stones (23.3%) were larger than 100 mm 2. In the group II, 26 stones (70.3%) were impacted, and 11 stones (29.7%) were larger than 100 mm 2. Stones were defined as impacted by the ra-diographic, echosonographic as well as endoscopic findings in the group II of patients. Stone size was presented in mm 2. Chemical composition of stones were almost the same in both groups of the patients. Results. Generally, there was no statistically significant difference in the treatment success between the groups. However, stones larger than 100 mm 2 were statistically more successfully treated endoscopically, while there was no statistical difference in the treatment success of impacted stones between these two groups. Conclusion. ESWL can by considered as primary first therapeutic approach in treatment of all proximal urete-ral stones except for stones larger than 100 mm 2 that should primarily be treated endoscopically.


Introduction
Extracorporeal shock wave lithotripsy (ESWL) and ureteroscopic lithotriptors developed in the last two decades of the 20th century represent a revolution in urology and lead to modern era -an era of minimally invasive therapy of ureteric stones.Before 1992 ESWL was considered to be the first therapeutic choice for ureteral stones in all parts of ureter.Later studies, however, revealed better results of distal ureteral stones treatment by ureteroscopic approach 1,2 .Till now ESWL has been considered as first treatment option for lumbar ureteral stones because of lower complications rate and auxiliary procedures rate, comparing to ureteroscopic treatment.The question of first therapeutic approach to ureteral stone removal is still contraversial expecially for stones located in the proximal part of ureter.Large number of investigators did not find significant difference in treatment success between ESWL and ureteroscopy, regarding proximal ureteral stone localization [3][4][5][6][7][8] .Beside that, some authors reported even better results of proximal ureteral stone treatment with ureteroscopic lithotripsy than with ESWL [9][10][11] .For these reasons, there is a certain need to investigate which factors have influence on proximal ureteral stones lithotripsy effectiveness, as well as what would be the first therapeutic choice.
So, the aim of our study was to investigate the influence of stone impaction and size on proximal ureteral stones lithotripsy effectiveness.

Methods
A total of 123 patients with proximal ureteral stones were investigated in this prospective study performed in a 10 months period.Patients were divided in the group I -86 patients treated with ESWL (Siemens Lithostar, Germany) and the group II -37 patients treated ureteroscopically with "Swiss" Lithoclast (EMS, Switzerland).Indications for treatment were also the same in both groups of the patients: stone size 7 mm with probability of spontaneous elimination less than 20%, or the absence of spontaneous stone elimination in a more than 30-day period of clinical evolution, with standard stone visualization diagnostic procedures performed (echosonography, kidneys, ureters and bladder radiography -KUB, intravenous urography).In the group I 49 stones (57.0%) were classified as impacted, and 20 stones (23.3%) were larger than 100 mm 2 .In the group II 26 stones (70.3%) were impacted, and 11 stones (29.7%) larger than 100 mm 2 .Stone were defined as impacted by the following diagnostic criteria: persistent or worsened hydronephrosis on successive echosonograms (Figure 1) or contrast radiograms (Figure 2) and by endoscopic findings such as edema and ureteral mucosa inflammation around and distal of stone impaction.Stone size was presented in mm 2 .
Lithotripsy efficiency was estimated by echosonography and KUB performed 10-14 days after the procedure in the group I, immediately or one day after the procedure in the group II and after three monts in both groups of the patients.Statistical difference of obtained data was analysed by χ 2 test.

Results
There was no difference in distribution of patients regarding age and male/female ratio.The group I of patients consisted of 51 men, age 25-77 (average 53.1) years and 35 women, age 18-80 (average 50.2) years.The group II of patients consisted of 27 men, age 17-76 (average 49.3) years and 10 women, age 29-74 (average 51.8) years.Chemical composition of stones were investigated by X-ray diffraction and were almost the same in both groups of the patients, with predominance of calcium-oxalate in more than 60% of the cases.Calcium-oxalate monohydrate was predominant in more than 50% of calcium-oxalate stones.
Stone impaction was analized in Table 1.There were no statistical difference in the number of impacted stones between the groups I and II (χ 2 = 1.921, p > 0.05).  2 showed no statistical difference in the number of stones larger than 100 mm 2 between the two groups of the patients (χ 2 = 0.575, p > 0.05).
There were no significant difference in disintegration success between the two groups (χ 2 = 0.235, p > 0.05) (Table 3).Success was defined as the abscence of stone fragments on KUB peformed up to three months after the treatment.Partial success was defined as the presence of fragments, smaller than stone burden before lithotripsy, even three months after the procedure.The presence of stone unchanged size after procedure was defined as unsucces.
In spite of procentual superiority of ballistic lithotripsy to ESWL regarding the number of successful procedures as shown in Table 4, statistical analysis, however, revealed no significant difference between the two groups of patients in impacted proximal ureteral stone treatment success (χ 2 = 2.605, p > 0.05).
Unlike stone impaction, analysis of influence of stone size on lithotripsy success showed that proximal ureteral stones larger than 100 mm 2 were significantly more successfully treated with Lithoclast than with ESWL (χ 2 = 4.045, p < 0.05) (Table 5).

Discussion
Advancements in medical technology for urolithiasis treatment mode after 1980 brought significant advantages.Comparing to ureterolithotomy, ESWL and ureteroscopic procedures are minimally invasive therapeutic approaches for those ureteral stones that cannot be eliminated spontaneously due to their size or degree of impaction either.The advantages of these two therapeutic approaches are well known: possibility of treatment in analgesia or analgosedation and consequently in outpatient unit, less frequent intraas well as postoperative complications and less working inability of patients.In order to make ureteric stone treatment more efficient and rational, question of gold therapeutic standard -primary therapeutic choice, is arising.Having in mind similar success rate of ESWL and uretoscopic procedures, ESWL was considered favorable for proximal ureteral stones treatment due to lower complication rate comparing to ureteroscopic treatment.Additionally, there are many reports demonstrating that retrograde stone propulsion during procedure is the most common cause of unsuccessful endoscopic treatment.Reported success for ureteral stone treatment was from 71%, with 28.9% retrograde propulsion of stone fragments 12 , to 100%, but with retrograde fragment propulsions registrated in 48% of cases 13 .Percentage of retrograde stone propulsion varied from just 5.5% 14 , to even 60% 15 .In such cases additional ESWL treatment was necessary.In our study endoscopic lithotripsy of proximal ureteral stones was successful in 73% of cases with 21.6% retrograde stone propulsions.Puppo et al. 9 reported the success of 93.6% regardless stone localization and recommended ballistic lithotripsy with "Swiss" Lithoclast as first therapeutic options for all ureteral stones.
In our study ESWL was successful in 68.6% of the cases.Gonzales et al. 4 on the other side reported 97% successful ESWL procedures in their study.Regarding percentage of "stone free" outcomes, large numbers of authors emphasize stone size, stone impaction and chemical structure as the most important factors influencing ESWL success 4,16 .
Based on the results obtained comparing ESWL with Modulith SL20 device and "Swiss" Lithoclast treatment of ureteral stones, Eden et al. 10 concluded that ESWL is optimal treatment for stone size below 8 mm, while for stones larger than 8 mm and multiple stones Lithoclast should be first therapeutic option.Eden's attitude was also confirmed by other authors 4,[17][18][19][20][21] .Kim et al. 22 achieved cumulative "stone free" status with Siemens Lithostar: 100% for stone smaller than 5 mm, 90% for stones 6-10 mm, 87% for stones 11-15 mm, 70% for stones 16-20 mm, 67% for stones 21-25 mm and only 50% for stones larger than 25 mm and thus concluded that ureteral stone size has very important influence on ESWL outcome (p < 0.01).Our study also confirms the results of Kim's 22 study, by 72.7% success rate for Lithoclast lithotripsy comparing to only 35% success ac-complished with ESWL for ureteral stones larger than 100 mm 2 (p < 0.05).
One of the factors that can influence ureteral stone minimally invasive treatment outcome is stone impaction.Dretler and Weinstein 23 reported in 1988 the opinion that impacted ureteral stone should be primarily treated endosopically.Later reports 24,25 confirmed the opinion of Yagisawa et al. 26 too, by 91% successful pneumatic ureteroscopic lithotripsies of impacted ureteral stones and only 9% failed lithotripsies due to retrograde stone propulsion or sharp ureteric curve below a stone site.By other authors attitudes 27 , the best therapeutic effect in cases of impacted stone can be achieved by stone pushing back from ureter to kidney and than its ESWL treatment.On the other side, Srivastava et al. 28 achieved 93% successful results by in situ ESWL treatment of no impacted ureteral stones and only 35% successful results in impacted stones group.Kim et al. 22 also confirmed a high influence of ureteral stone impaction on ESWL outcome.In their study, ESWL of ureteral stones was 100% successful in no obstructed ureter, 80% successful in mild obstructed ureter and only 50% successful in completely obstructed ureter (defined as an absence of contrast excretion from obstructed kidney).Other authors, however, consider that ESWL of impacted stone in ureter is a therapeutic method of choice, but not in cases of high degree of stone impaction in whom previous urine drainage is indicated 11 .For such cases ureteroscopic lithotripsy should be primarily performed.Statistical analysis of our study, in spite of 73% successful Lithoclast lithotripsies and 53% successful ESWL treatments, did not confirm a significant influence of stone impaction on ESWL and Lithoclast treatment success.The results of our study are at least statistically consonant with Sinha's et al. 29 results by which ESWL of impacted and no impacted ureteral stones were equally successful -in 76.7% of cases (stones were defined as impacted in cases of no visualization of contrast distal of stone site).Among factors that influence ESWL successfulness, such are stone impaction, localization, number of stones, first ESWL session failure and patient sex, age and obesity, stone size and distal ureteral stone localization alone have the strongest negative influence on ESWL treatment outcome 16,19 .

Conclusion
The results of our study showed no statistically significant difference between "Swiss" Lithoclast and ESWL in proximal ureteral stones treatment.Evaluation of stone impaction and stone size influence on treatment success showed significantly more efficient treatment of proximal ureteral stones larger than 100 mm 2 with Lithoclast, while stone impaction had no influence on the tretament efficiency difference between two methods.Based on these results, ESWL should be considered as first therapeutic approach for all proximal ureteral stones, except for stones larger than 100 mm 2 that should be primarily treated endoscopically.

Table 1 Proximal ureteric stone impaction in patients treated with extracorporeal shock wave lithotripsy (group I) and "Swiss" Lithoclast (group II)
) mm 2 with stones larger than 100 mm 2 in 23.3% of cases.In the group II stone size varied from 15 to 275 (averagely 86.7) mm 2 , with stones larger than 100 mm 2 registrated in 29.7% of patients.Analysis of data from Table