What is the optimal size of renal stones for treatment with lithotripsy?

From the Guidelines

The optimal size of renal stones for treatment with lithotripsy is generally less than 2 cm, with stones less than 1 cm having a 90% stone-free rate, as reported in the most recent study 1.

Key Considerations

• Stones smaller than 5mm often pass spontaneously without intervention, making lithotripsy unnecessary.
• Stones larger than 2 cm typically respond better to alternative treatments such as percutaneous nephrolithotomy (PCNL) or ureteroscopy.
• Location also matters - stones in the renal pelvis or upper/middle calyces respond better than those in the lower pole where gravity makes fragment clearance more difficult.
• Stone composition affects outcomes too, with calcium oxalate dihydrate and uric acid stones fragmenting more easily than calcium oxalate monohydrate or cystine stones.

Treatment Outcomes

• The effectiveness of lithotripsy depends on these factors because the shock waves must be able to adequately fragment the stone while allowing the body to naturally clear the resulting pieces through the urinary tract.
• Patients should expect multiple sessions for stones closer to 2 cm, and should maintain good hydration before and after the procedure to help pass fragments, as suggested by the European Association of Urology guidelines 1.

Guideline Recommendations

• The European Association of Urology guidelines recommend extracorporeal shock wave lithotripsy (ESWL) as the first-line treatment for pediatric patients with kidney stones less than 2 cm 1.
• Flexible ureteroscopy (FURS) is considered a secondary option for all upper tract stones according to EAU guidelines due to the lack of high-level evidence on the subject 1.

From the Research

Optimal Size of Renal Stones for Lithotripsy

The optimal size of renal stones for treatment with lithotripsy is a topic of ongoing research and debate.

• Studies have shown that lithotripsy can be effective for stones up to 2 cm in size 2.
• For stones larger than 2 cm, percutaneous nephrolithotomy (PCNL) is often recommended as the first-line treatment, but lithotripsy can still be considered in selected cases 3, 4.
• The American Urological Association (AUA) guidelines suggest that shock wave lithotripsy (SWL) is a viable option for stones up to 2 cm in size, but the success rate decreases for larger stones 5, 6.
• Flexible ureteroscopy can be an option for lower pole stones between 1.5 and 2 cm in size, especially in cases with difficult anatomy or ESWL-resistant stones 6.

Stone Size and Treatment Outcomes

The outcome of lithotripsy treatment is influenced by the size of the renal stone.

• Studies have reported high stone-free rates for stones up to 2 cm in size, with success rates ranging from 80% to 90% 3, 4, 2.
• For larger stones, the stone-free rate decreases, and multiple procedures may be required to achieve optimal results 3, 4.
• The choice of treatment modality should be individualized based on the patient's anatomy, comorbidities, and preferences, as well as the size and location of the stone 2, 6.

Considerations for Lithotripsy Treatment

When considering lithotripsy treatment for renal stones, several factors should be taken into account.

• Stone composition and density can affect the success of lithotripsy treatment 5.
• Patient positioning and coupling are critical to ensure optimal energy delivery and minimize complications 5.
• Medical expulsive therapy with alpha-blockers may be beneficial after SWL treatment, especially for stones larger than 10 mm 5.
• The decision to use lithotripsy should be based on a comprehensive evaluation of the patient's condition and the potential benefits and risks of treatment 6.