What is the best treatment for a 9 mm stone in the mid-lower pole of the kidney?

Management of a 9 mm Stone in the Mid-Lower Pole of the Kidney

For a 9 mm stone in the mid-lower pole of the kidney, either shock wave lithotripsy (SWL) or ureteroscopy (URS) should be offered as first-line treatment options, with URS potentially offering higher stone-free rates but SWL providing better quality of life measures. 1

Treatment Options Based on Stone Size and Location

First-Line Treatment Options

• Stone size ≤10 mm in lower pole: Both SWL and URS are recommended as first-line treatments 1
  • A multi-center prospective randomized trial found no statistically significant difference in stone-free rates between URS and SWL for lower pole stones ≤10 mm 1
  • Intraoperative complications were somewhat higher with URS but not statistically significant
  • Patient-derived quality of life measures were somewhat better with SWL

Factors to Consider When Choosing Between SWL and URS

1. Stone characteristics:

   • Stone composition and density
   • Lower pole anatomy (infundibulopelvic angle, infundibular width, infundibular length)

2. Patient factors:

   • Obesity
   • Skin-to-stone distance
   • Bleeding diathesis
   • Anticoagulation therapy that cannot be discontinued (favors URS) 1
   • Patient preference regarding stent discomfort vs. potential need for multiple SWL sessions

Procedural Considerations

For Shock Wave Lithotripsy (SWL)

• No pre-stenting is recommended before SWL 1
• Consider α-blockers after SWL to facilitate passage of stone fragments 1
• If initial SWL fails, an endoscopic approach is recommended 1
• Success of SWL depends on:
  • Obesity
  • Skin-to-stone distance
  • Collecting system anatomy
  • Stone composition and density 1

For Ureteroscopy (URS)

• Use of a safety wire is recommended 1
• Laser lithotripsy is preferred for flexible URS 1
• Routine placement of a ureteral stent is not recommended preoperatively or postoperatively 1
• If stenting is required, α-blockers and anti-muscarinics can be prescribed to reduce stent discomfort 1
• For difficult-to-access lower pole stones:
  • A nitinol basket or grasper can be used to reposition the stone to a more favorable position for fragmentation 2, 3
  • This technique has shown 85% stone-free rates at 3 months 2

Follow-Up and Monitoring

• Follow-up imaging is recommended to assess stone clearance 1
• For residual fragments <4 mm without symptoms or infection, active monitoring can be considered 4
• Increase fluid intake to achieve urine output of at least 2.5 liters daily to prevent recurrence 5

Pitfalls to Avoid

1. Overtreatment of small asymptomatic stones that are likely to remain stable 5
2. Underestimating the importance of stone composition when selecting treatment modality
3. Failing to consider patient-specific factors such as obesity or bleeding disorders that may affect treatment success
4. Not providing adequate follow-up to ensure stone clearance and prevent recurrence

When to Consider Alternative Approaches

• If both SWL and URS fail, percutaneous nephrolithotomy (PCNL) may be considered, though this is typically reserved for stones >20 mm 1
• For stones between 10-20 mm in the lower pole, URS or PCNL are preferred over SWL 1

In summary, for a 9 mm stone in the mid-lower pole of the kidney, both SWL and URS are appropriate first-line treatment options with comparable stone-free rates. The final choice should be based on stone characteristics, patient factors, and available expertise.