A Prospective Randomized Comparison Between Shockwave Lithotripsy and Semirigid Ureteroscopy for Upper Ureteral Stones <2 cm: A Single Center Experience

Abstract

Background and Purpose:

The best management of upper ureteral calculi is undefined. We performed a prospective randomized comparison between semirigid ureteroscopy (URS) and shockwave lithotripsy (SWL) for upper ureteral stones <2 cm to evaluate safety and efficacy of both procedures.

Patients and Methods:

Patients with a single radiopaque upper ureteral stone <2 cm undergoing treatment between January 2010 and May 2011 in our department were included. Randomization was performed into two groups—group A: SWL performed as an outpatient procedure using an electromagnetic lithotripter (Dornier Compact Delta); group B: URS performed using an 6/7.5F semirigid ureteroscope with holmium laser intracorporeal lithotripsy. Statistical analysis was performed regarding demographic profile, success rates, retreatment rates, auxiliary procedures, and complications.

Results:

There were 90 patients enrolled in each group. Mean stone size: 12.3 mm in group A vs 12.5 mm in group B (P=0.52). The overall 3-month stone-free rate was (74/90) 82.2% for group A vs (78/90) 86.6% for group B (P=0.34). For stone size <10 mm, 3-month stone-free rates were (45/53) 84.9% for group A vs (43/49) 87.7% for group B (P=0.32). For 10 to 20 mm stones, 3-month stone-free rates were (29/37) 78.4% for group A vs (35/41) 85.4% for group B (P=0.12).The re-treatment rate was significantly greater in group A than group B (61.1% vs 1.1%, respectively; P<0.001). The auxiliary procedure rate was comparable in both groups (21.1% vs 17.7%; P=0.45). The complication rate was 6.6% in group A vs 11.1% in group B (P=0.21).

Conclusions:

Both SWL and semirigid URS are safe and highly efficacious for treating patients with proximal ureteral stones <20 mm. For stones <10 mm, SWL was safer, less invasive, and of comparable efficacy with URS. For stones between 10 and 20 mm, however, URS was more effective, with a lesser re-treatment rate.

Introduction

Management options for proximal ureteral calculi include medical expulsive therapy, shockwave lithotripsy (SWL), ureteroscopy (URS), percutaneous antegrade URS, laparoscopy, and open surgical ureterolithotomy.¹ The optimal method for upper ureteral stones is evolving in the line of less invasive procedures. URS and SWL both are minimally invasive methods of management for upper ureteral stones. SWL is noninvasive and is a procedure with low morbidity. Its efficacy decreases, however, as stone size increases.^2,3 There is also need for repeated sittings in a substantial fraction of patients.¹

The introduction of small-caliber semirigid ureteroscopes, as well as the development of effective intracorporeal lithotripsy methods, especially the holmium laser, has substantially improved the URS stone-free rates and greatly decreased the complication rates.^4

–8 Patients undergoing URS, however, need hospitalization, regional or general anesthesia, and considerable surgical skill. Therefore, the optimal management of upper ureteral stones still remains a debate. Prospective randomized studies comparing both the modalities are few, however.⁹ We conducted a prospective randomized study comparing the outcome, safety, and efficacy of SWL and URS to establish the optimal treatment modality for the management of solitary radiopaque upper ureteral calculi less than 2 cm in diameter.

Patients and Methods

The study protocol and all the procedures were approved by the institutional ethical committee. Between January 2010 and May 2011, consecutive patients attending the urology outpatient department with a single upper ureteral radiopaque calculus less than 2 cm, who satisfied eligibility criteria, and who were planned for either SWL or URS were enrolled for this prospective randomized study. The ureter between the pelviureteral junction and the upper border of the sacroiliac joint was defined as the upper ureter.

Patients with a stone larger than 2 cm, bleeding disorders, radiolucent stones, active urinary tract infection, age >60 years and <15 years, severe hydronephrosis, weight >100 kg and <40 kg, comorbid cardiovascular and respiratory illnesses, pregnancy, fever >37^°C, serum creatinine level >1.5 mg/dL, total leucocyte count >12,000/dL, solitary kidney, coexisting ureteral pathology including tumor/stricture, and those who did not give written informed consent were excluded from the study.

The eligible patients were randomized into two groups (groups A and B) using a computer generated randomization table. Each group was further divided into two subgroups on the basis of stone size: Subgroups A1 and B1 with stone size≤1 cm and subgroups A2 and B2 with stone size 1 to 2 cm.

Initial evaluation included a detailed clinical history, blood and urine investigations including a complete hemogram; liver function test; kidney function test; serum calcium, serum phosphate, and serum uric acid evaluations; urine routine microscopy; urine culture sensitivity; and a 24-hour urine analysis including calcium, phosphate and uric acid levels. Ultrasonography of the kidneys, ureters, and bladder (KUB), radiography of the KUB (to assess radiopacity of the calculus), and a noncontrast CT with three-dimensional reconstruction (to know the location and size of the calculus) was performed.

In the SWL group (group A), SWL was performed as an outpatient procedure using the Dornier Compact Delta (Dornier Medizintechnik GmbH, Germering, Germany). Five grams of eutectic mixture of lidocaine and prilocaine was applied on an approximately 30 cm² skin area corresponding to the entry site of the shockwaves, 60 minutes before the procedure. A tablet of diclofenac sodium (dosage: 50 mg for body weight <70 kg, 100 mg for >70 kg) was given orally at the same time. The shockwave was delivered at a rate of 100 impulses per minute. Three thousand shockwaves were the maximum number of shockwaves to be given per session. During each session, the patient was observed for 2 hours. KUB radiography and ultrasonography were used to check stone fragmentation and clearance after each session at 2 weeks. Re-treatment SWL was given for incomplete clearance. A maximum of four sessions of SWL were given. URS and percutaneous nephrolithotomy were the auxillary procedures performed after failed SWL.

In the URS group (group B), the procedure was performed using an 6/7.5F semirigid ureteroscope (Richard Wolf, Knittlingen, Germany). The holmium laser (Lumenis Versa plus 100 watt, Lumenis Ltd., Yokneam, Israel) was used for intracorporeal lithotripsy. The power setting of holmium laser was 0.6 to 1.2 J. The pulse rate was set between 5 and 15 Hz. The ureteral orifice was dilated as needed and in cases of large stone burden; a Double-J stent was kept in situ. Extravasation or perforation of the ureter also mandated placement of a Double-J stent. Stent removal was performed 4 weeks after surgery.

Parameters studied in both the groups were: Patient demographics, stone characteristics, analgesic characteristics (supplemental analgesia, adverse effects), and treatment details. The outcome variables in both groups were the re-treatment rates and the stone-free status at 3 months, modified efficiency quotient (EQ), and auxiliary procedure rates. Stone-free status after the initial SWL session or URS was defined as radiologic absence of stone, asymptomatic patients with stone fragment <3 mm, and sterile urine culture at 3 months or earlier. Modified EQ was used to distinguish between patients who became stone free by SWL/URS alone and those who were stone free by an auxiliary procedure.

Observations were recorded and arranged on a Microsoft Excel spreadsheet (Microsoft, Seattle, WA) and analyzed by SPSS software version 17.0. A chi-square test was used for categorical variables. The Student t test and Wilcoxon rank sum test (group A/B, A1/A2, B1/B2) were used for continuous variables. A P value<0.05 was considered significant.

Results

A total of 244 patients reported with a single upper ureteral radiopaque calculus <2 cm, of whom 54 patients were excluded because they failed to satisfy the eligibility criteria. The 190 patients included in the study were randomized into two groups using a computer generated randomization table: 94 patients in group A and 96 patients in group B. Ten patients (4 from the SWL group and 6 from the URS group) were lost to follow-up. Therefore, a total of 180 patients were analyzed in the study. The subgroups A1, A2, B1, and B2 had 53, 37, 49, and 41 patients, respectively (Fig. 1). The demographic characteristics of the patients and stone location and size are listed in Table 1. The mean age, sex ratio, mean height, and mean weight as well as stone location (right/left) and stone size of the study subjects were comparable between the groups and the subgroups.

FIG. 1.

Flow diagram: Progress through the phases of the trial.

Table 1.

Baseline Characteristics of the Study Subjects and Calculi in Both Groups

	Group A			Group B
	A1 (<1 cm)	A2 (1–2 cm)	Total	B1 (<1 cm)	B2 (1–2 cm)	Total	P value
Number	53	37	90	49	41	90	0.32 (NS)
Mean age (years)	36.1±2.1	37.3±2.2	36.7±2.4	35.1±1.9	36.3±2.3	35.6±2.1	0.22 (NS)
Sex (male/female)	24/29	20/17	44/46	25/24	21/20	46/44	0.14 (NS)
Mean height (cm)	163.2±1.9	164.1±1.5	163.7±1.6	164.2±1.3	163.7±1.2	163.4±1.4	0.18 (NS)
Mean weight (kg)	62.3±1.5	63.1±1.2	62.6±1.4	61.6±1.3	62.5±1.2	61.5±1.3	0.41 (NS)
Stone location (right/left)	27/26	21/16	48/42	25/24	21/20	46/44	0.35 (NS)
Mean stone size (cm)	7.9±1.1	15.2±1.3	12.3±1.2	7.7±1.3	15. 3±1.2	12.5±1.1	0.52 (NS)
Hydronephrosis
None	27	20	47	26	20	46	0.41 (NS)
Mild	21	10	31	17	12	29	0.33 (NS)
Moderate	5	7	12	6	9	15	0.37 (NS)

Group A-SWL group: A1, stone size <10 mm; A2, stone size >10 mm.

Group B-URS group: B1, stone size <10 mm; B2, stone size >10 mm.

NS=not significant.

The treatment outcomes are summarized in Table 2. The operative time between the subgroups was not significantly different. The re-treatment rate was significantly higher in the SWL group. The number of auxiliary procedure needed was higher in group A1 compared with B1 and B2 compared with A2, but the difference was not statistically significant.

Table 2.

Treatment Outcomes of the Study Subjects

	Group A			Group B
	A1 (<1 cm)	A2 (1–2 cm)	Total	B1 (<1 cm)	B2 (1–2 cm)	Total	P value
Mean operative time (min)	41.1±1.8	49.2±1.7	45.3±2.1	30.3±1.2	39.1±1.5	35.5±1.9	0.31 (NS)
Re-treatment rate (%)	25 (47.2)	29 (78.4)	54 (61.1)	3 (6.1)	7 (17)	10 (1.1)	<0.001 (S)
Auxiliary procedures rate (%)	9 (16.7)	10 (27)	19 (21.1)	4 (8.1)	12 (29.3)	16 (17.7)	0.45 (NS)
Stone-free rate–3 months (%)	45 (84.9)	29 (78.4)	74 (82.2)	43 (87.7)	35 (85.4)	78 (86.6)	0.34 (NS)
Modified EQ (%)	^*69.1	^**46.4	67.3	^*89.2	^**83.4	85.2	^0.32 (NS) ^*0.01 (S)

Group A-SWL group: A1, stone size <10 mm; A2, stone size >10 mm.

Group B-URS group: B1, stone size <10 mm; B2, stone size >10 mm.

S=not significant; S=significant; EQ=efficiency quotient.

=A₁ vs B₁; ^**=A₂ vs B₂.

The stone composition between the subgroups was comparable (Table 3), and it had no effect on treatment outcome. The stone-free rate at 3 months, although comparable in each subgroup, was higher in the URS group. Modified EQ, which includes the re-treatment rate of each patient for complete stone clearance, was significantly higher in group B2 compared with A2, but the difference between the groups A1 and B1 was not statistically significant.

Table 3.

Stone Composition in Different Groups

Stone composition	A1	A2	Total	B1	B2	Total	P value
Calcium oxalate monohydrate	31	17	48 (53.3)	29	18	47 (59.2)	0.11 (NS)
Calcium oxalate dehydrate	6	5	11 (12.2)	6	7	13 (14.4)	0.32 (NS)
Calcium carbonate	7	5	12 (13.3)	5	6	11 (12.2)	0.41 (NS)
Calcium phosphate	7	6	13 (14.4)	8	6	14 (15.5)	0.25 (NS)
Cysteine	3	3	6 (6.6)	2	3	5 (5.5)	0.36 (NS)

Group A-SWL group: A1, stone size <10 mm; A2, stone size >10 mm.

Group B-URS group: B1, stone size <10 mm; B2, stone size >10 mm.

NS=not significant.

The complication rates between the subgroups are summarized in Table 4. In group A, the most common complication was severe pain, which could be managed with parenteral analgesics, and in group B, it was urinary tract infection, managed with oral antibiotics. Of 180 patients, only 2 patients, 1 in each group, had gross hematuria, but it could be managed conservatively without any blood transfusion. There were no deaths in either group.

Table 4.

Comparison of Complication Rates in Both Groups

	Group A			Group B
Complications (%)	A1 (<1 cm)N (%)	A2 (1–2 cm)N (%)	Total	B1 (<1 cm)	B2 (1–2 cm)	Total	P value
Urinary tract infection	0	2 (5.4)	2 (2.2)	1 (2)	2 (4.8)	3 (3.3)	0.32 (NS)
Gross hematuria	0	1 (2.7)	1 (1.1)	0	1 (2.4)	1 (1.1)	0.22 (NS)
Severe pain	1 (1.8)	2 (5.4)	3 (3.3)	1 (2)	1 (2.4)	2 (2.2)	0.14 (NS)
Stone up-migration	0	0	0	1 (2)	3 (7.3)	4 (4.4)
Total	1 (1.8)	5 (13.5)	6 (6.6)	3 (6.1)	7 (17)	10 (11.1)	0.21 (NS)

Group A-SWL group: A1, stone size <10 mm; A2, stone size >10 mm.

Group B-URS group: B1, stone size <10 mm; B2, stone size >10 mm.

NS=not significant.

Discussion

Medical expulsive therapy has been described as an important modality of management in ureteral stones. The success rate depends on stone size, and stones <5 mm are more likely to be expulsed by medical management. The majority of upper ureteral stones, however, need intervention, because the spontaneous expulsion rate is only 22%.¹⁰ Management options of upper ureteral calculi depend on various factors such as size of the stone, associated pain, duration, obstructed or nonobstructed, cost, and availability of instrument.¹¹

SWL and URS are the two most common modalities used for the management of upper ureteral calculi.¹² Both procedures have advantages and disadvantages, and there are proponents for each of them. Prospective studies comparing the two modalities are limited.⁸

The proponents of SWL tout for its noninvasiveness, safety, and nonrequirement of any anesthesia. It does not require significant surgical skills. It can be performed as an outpatient procedure. The invention of newer generation machines require less analgesia and also cause less tissue injury.^13,14 SWL requires multiple sessions, however, and has a high initial cost of establishment.

On the other hand, URS provides immediate stone-free status in a single sitting and a lower re-treatment rate, but it is invasive and has more complications. It requires anesthesia and considerable surgical skill.

In our study, we found that for stones <10 mm, efficacy and safety of SWL and URS were comparable. The stone-free rate at 3 months for both procedures was same—ie, more than 80%. The result is similar to the result of previous studies.^5,9 In a prospective randomized study, Salem and associates⁹ found that for stones <1 cm, the initial stone-free rate for URS and SWL was 100% and 80%, respectively. In another study comparing 46 procedures for upper ureteral stones <1 cm, Lam and colleagues⁵ found that the initial stone-free rate was 100% and 80% for ureteroscopic laser lithotripsy and SWL, respectively. In our study, the overall re-treatment rate for SWL was significantly higher than URS. When we calculated the modified EQ, however, the difference was not significant.

For stones 1 to 2 cm, the efficacy of URS was better than SWL, which was reflected by the lower re-treatment rate and higher modified EQ. The stone-free rate at 3 months was higher with URS, but the difference was not statistically significant. In the study by Salem and coworkers,⁹ it was found that for stones ≥1 cm, the initial stone-free rates for URS and SWL were 88% and 60%, respectively, whereas Lam and associates⁵ found that the initial stone-free rate in patients with calculi 1 cm or larger was 93% for URS with holmium:yttrium-aluminum-garnet laser lithotripsy and 50% for in situ SWL.

In the present study, the stone size did not significantly affect the outcome of URS (87.7% vs 84.9%), but the efficacy of SWL decreased as the stone sizes increased (84.9% vs 78.4%). This finding was in concordance with the findings of Lam and colleagues.⁵ The stone composition did not affect the outcome of results in either modality, and this was similar to the findings of Singh and coworkers.¹⁵

In the present study, the complication rate of both the procedures was acceptable and did not vary significantly with stone size. It has been proven from previous studies that SWL is a safe procedure. Its efficacy depends mainly on stone size apart from stone location. SWL is an outpatient procedure and does not need admission. Its cost-effectiveness is established from previous studies.¹⁶

The safety of URS is also documented, and with the advancement of technologies such as semirigid scopes, holmium laser fibers, etc., the complications are still decreasing. The main advantage of URS is a stone-free rate in a single sitting. The re-treatment rate is very low. It is best for those patients who stay away from healthcare settings and work in high risk jobsuch as pilots, drivers, and soldiers.

Conclusion

SWL and URS both are safe and highly efficacious in the management of upper ureteral stones <20 mm. For upper ureteral stones <10 mm, SWL is safer, less invasive, and of comparable efficacy as URS. For upper ureteral stones 10 to 20 mm, URS is more effective and has a lower re-treatment rate than SWL.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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