When is lithotripsy (extracorporeal shock wave lithotripsy) recommended for patients with kidney stones?

When is Lithotripsy Recommended for Kidney Stones?

Extracorporeal shock wave lithotripsy (ESWL/SWL) is recommended as first-line treatment for renal stones less than 20 mm located in the renal pelvis or upper/middle calix, and for lower pole stones less than 10 mm, but should NOT be used for most staghorn calculi, stones greater than 20 mm, or cystine stones. 1

Stone Size and Location Determine Treatment Choice

Renal Pelvis and Upper/Middle Calix Stones

• For stones <20 mm: SWL and flexible ureteroscopy (fURS) are both first-line options with equivalent recommendations 1
• For stones 10-20 mm: Percutaneous nephrolithotomy (PCNL) is also an acceptable option alongside SWL and fURS 1
• For stones >20 mm: PCNL becomes the preferred first-line treatment, not SWL 1

Lower Pole Stones (Special Considerations)

• For stones <10 mm: SWL or fURS are appropriate first-line options 1
• For stones 10-20 mm: fURS and PCNL are preferred; SWL has significantly lower success rates (median 58% vs 81% for URS and 87% for PCNL) 1
• For stones >20 mm: SWL should NOT be offered as first-line therapy due to poor outcomes (median success rate only 10%) 1
• Unfavorable lower pole anatomy (steep infundibulopelvic angle, long infundibulum, narrow infundibulum) reduces SWL stone-free rates to approximately 50% 2

Ureteral Stones

Distal Ureteral Stones

• For stones <10 mm: Ureteroscopy (URS) is first-line per AUA guidelines, though SWL is considered equivalent by EAU and SIU/ICUD guidelines 1
• For stones >10 mm: URS is universally recommended as first-line treatment across all major guidelines 1

Proximal Ureteral Stones

• For stones <10 mm: URS is first-line, with SWL as an equivalent option per EAU and AUA guidelines 1
• For stones >10 mm: URS is recommended as first surgical modality, though SIU/ICUD guidelines suggest SWL as first-line for this specific scenario 1

When SWL Should NOT Be Used

Staghorn Calculi

• SWL monotherapy should NOT be used for most patients with staghorn calculi due to significantly inferior stone-free rates compared to PCNL-based therapy 1
• A randomized trial showed PCNL stone-free rates were more than three times greater than SWL monotherapy for staghorn stones 1
• Exception: SWL monotherapy may be considered only for small volume staghorn calculi (<500 mm²) with normal collecting system anatomy, and must be combined with renal drainage via ureteral stenting or percutaneous nephrostomy 1

Cystine Stones

• SWL monotherapy should NOT be used for staghorn or partial staghorn cystine stones due to poor stone-free rates 1, 3
• Cystine stones are among the hardest to fragment with shock-wave therapy due to their structural characteristics 3
• Small cystine stones (<10 mm) may respond to SWL, but with lower expectations for success compared to other stone compositions 3
• Smooth-contoured cystine stones have higher CT attenuation values and are more resistant to fragmentation than rough-appearing stones 3

Mandatory Requirements When Using SWL

Drainage Requirements

• Adequate drainage of the treated renal unit must be established before SWL treatment via internal ureteral stent or percutaneous nephrostomy tube to facilitate fragment passage, prevent severe obstruction, and limit sepsis 1

Irrigation Requirements

• Normal saline must be used as irrigation solution during any stone procedure, as non-isotonic solutions increase risk of hemolysis, hyponatremia, and heart failure if absorbed 1

Post-SWL Management

• Alpha-blockers should be prescribed after SWL to facilitate passage of stone fragments 1
• If initial SWL fails, an endoscopic approach is recommended rather than repeat SWL 1

Relative Contraindications to SWL

• Patients on anticoagulation or antiplatelet therapy that cannot be discontinued (URS becomes preferred option) 1
• Presence of contractures, flexion deformities, or anatomic derangements preventing proper positioning 1
• Pregnancy (absolute contraindication)
• Active urinary tract infection without adequate drainage

Comparative Outcomes

SWL vs PCNL

• PCNL has higher three-month treatment success rates than SWL (RR 0.67, meaning SWL has 33% lower success) 4
• SWL leads to fewer complications than PCNL (62% relative risk reduction) 4

SWL vs RIRS

• RIRS has higher three-month treatment success rates than SWL (RR 0.85, meaning SWL has 15% lower success) 4
• Complication rates appear similar between the two modalities 4

Important Caveats

• Stone-free status is the critical outcome: While 98% of stones can be fragmented by SWL, the kidney and ureter's ability to clear resulting fragments is far more important for successful treatment 2
• Long-term safety concerns: SWL can cause vascular trauma to the kidney with potential for scarring and permanent loss of functional renal volume 5, 6
• Pediatric considerations: SWL is not FDA-approved for children, and animal studies suggest the developing kidney may be more susceptible to bioeffects of SWL, though recent reports indicate renal damage is mild and transient 1
• Follow-up is mandatory: Residual fragments can lead to regrowth and progression, requiring ongoing monitoring 2