What is the role of Extracorporeal Shock Wave Lithotripsy (ESWL) in treating kidney stones?

Role of ESWL in Treating Kidney Stones

ESWL is an acceptable first-line treatment for symptomatic kidney stones ≤20 mm (except lower pole stones >10 mm), but ureteroscopy achieves higher stone-free rates with fewer repeat procedures, making it the preferred option when both are available. 1

Treatment Selection Algorithm by Stone Size and Location

Stones ≤10 mm (Non-Lower Pole)

• Offer either ESWL or URS as first-line options with acceptable stone-free rates for cumulative stone burdens <20 mm 1
• ESWL achieves stone-free rates of approximately 72-90% for stones <10 mm depending on location 2, 3
• URS provides higher stone-free rates (90%) compared to ESWL (72%) and lower likelihood of repeat procedures, allowing patients to become stone-free more quickly 2
• Patient quality of life measures tend to be somewhat better with ESWL, though intraoperative complications may be slightly higher with URS (not statistically significant) 1, 2

Stones 10-20 mm (Non-Lower Pole)

• Both ESWL and URS remain acceptable options, but stone-free rates decline with increasing stone burden 1
• ESWL stone-free rates drop to approximately 60-80% for stones 10-20 mm 3
• URS is associated with lower likelihood of repeat procedures compared to ESWL 1
• The upper size limit for ESWL has been lowered to 15 mm due to increased risk of steinstrasse with larger sizes and potential need for anesthesia and ureteral stenting 4

Lower Pole Stones ≤10 mm

• Offer either ESWL or URS with no statistically significant difference in stone-free rates 1
• A multi-centered prospective randomized trial found comparable outcomes between modalities for 10 mm lower pole stones 1

Lower Pole Stones >10 mm

• Do not offer ESWL as first-line therapy 1
• For lower pole stones 10-20 mm, median success rate for ESWL is only 58% compared to 81% for URS and 87% for PCNL 1
• When stone burden exceeds 20 mm, ESWL success rate declines to 10% 1

Stones >20 mm (Any Location)

• Do not offer ESWL as first-line therapy 1
• PCNL should be offered as first-line treatment with higher stone-free rates (94% vs 75% for URS) 1
• ESWL is associated with significantly reduced stone-free rates and increased need for multiple treatments compared to PCNL 1

Critical Pre-Treatment Considerations

Mandatory Exclusions Before ESWL

• Rule out infection with obstruction immediately - if suspected, urgent drainage with nephrostomy tube or ureteral stent is mandatory before any definitive stone treatment 2
• Delay definitive treatment until infection is controlled with appropriate antibiotics 2

Patient-Specific Factors That Predict ESWL Failure

• Do not select ESWL for obese patients or those with unfavorable anatomy without recognizing these factors will significantly reduce success rates 1, 2
• ESWL success depends heavily on: obesity, skin-to-stone distance (SSD), collecting system anatomy, stone composition, and stone density (Hounsfield units) 1, 2
• Mean attenuation value (MAV) on CT is a better predictor of treatment success than stone size alone 5
• Patients selected for ESWL should generally have favorable parameters to maximize stone-free rates 1

Essential Imaging

• Obtain CT imaging as the gold standard for treatment planning and accurate stone burden measurement 2
• Measure stone in multiple dimensions using multiplanar CT measurements for more accurate representation of stone burden 2
• Document stone composition when feasible through analysis of previously passed stones or imaging characteristics 2

Comparative Outcomes: ESWL vs Other Modalities

ESWL vs PCNL

• ESWL has significantly lower three-month treatment success rate than PCNL (RR 0.67,95% CI 0.57 to 0.79) 6
• This corresponds to 304 fewer participants per 1000 achieving treatment success with ESWL 6
• ESWL probably leads to fewer complications than PCNL (RR 0.62,95% CI 0.47 to 0.82), corresponding to 82 fewer complications per 1000 participants 6
• Duration of treatment and hospital stay are significantly shorter with ESWL 7, 6

ESWL vs RIRS (Retrograde Intrarenal Surgery)

• ESWL has lower three-month treatment success rate than RIRS (RR 0.85,95% CI 0.78 to 0.93) 6
• This corresponds to 127 fewer participants per 1000 achieving treatment success with ESWL 6
• Complication rates between ESWL and RIRS show no significant difference (RR 0.93,95% CI 0.63 to 1.36) 6
• Mean procedural time and hospital stay are longer with RIRS 7

Pediatric Population Considerations

• In pediatric patients (<18 years) with renal stones <2 cm, flexible ureteroscopy has significantly higher stone-free rates than ESWL with no difference in complication rate or fluoroscopy exposure time 1
• ESWL remains first-line per European Association of Urology guidelines for pediatric stones <2 cm, but evidence suggests FURS may be superior 1
• ESWL in children has been used for several years with no long-term complications reported 1
• Given the weak evidence base, neither treatment modality can be definitively recommended over the other in pediatrics 1

Common Pitfalls to Avoid

• Do not routinely place stents before ESWL or after uncomplicated URS - this is not recommended and may negatively impact quality of life 2
• Do not use ESWL for staghorn calculi as first-line therapy - it is associated with higher risk of residual fragments and higher probability of unplanned procedures 1
• Avoid ESWL when patients have contraindications including use of anticoagulation or antiplatelet therapy that cannot be discontinued 1
• Do not ignore the increased risk of steinstrasse with stones >15 mm 4

Post-Treatment Management

• Stone analysis is crucial when stone material becomes available during or after treatment 2
• Re-treatment rates are significantly higher with ESWL compared to PCNL (RR 1.81,95% CI 0.66 to 4.99) 7
• Auxiliary procedures are significantly increased with ESWL compared to PCNL (RR 9.06,95% CI 1.20 to 68.64) 7