What are the procedures for treating kidney stones?

Kidney Stone Treatment Procedures

For kidney stones, treatment options include observation with medical expulsive therapy (MET) for small stones, while surgical interventions such as ureteroscopy (URS), shock wave lithotripsy (SWL), or percutaneous nephrolithotomy (PCNL) are recommended based on stone size, location, and composition. 1, 2

Initial Management and Assessment

• Urgent decompression is required in cases of obstructing stones with suspected infection via:

  • Ureteral stent placement
  • Percutaneous nephrostomy tube
  • This must be done before definitive stone treatment 1, 2

• Imaging: CT scan is the gold standard (97% sensitivity) for detecting kidney stones, while ultrasound (75% sensitivity) and KUB radiography are useful for monitoring 2

Treatment Algorithm Based on Stone Location and Size

Ureteral Stones

1. Stones ≤10 mm:

   • First-line: Observation with medical expulsive therapy (MET) using α-blockers, especially for distal ureteral stones 1, 2
   • If MET fails:
     • Distal stones: URS preferred (higher stone-free rates)
     • Proximal stones: SWL preferred
     • Mid-ureteral stones: Either SWL or URS 2

2. Stones >10 mm:

   • URS is generally preferred due to higher single-procedure success rates 2
   • Avoid electrohydraulic lithotripsy (EHL) as first-line for intra-ureteral lithotripsy due to risk of ureteral perforation 1

Renal Stones

1. Non-lower pole stones ≤20 mm:

   • Either SWL or URS (strong recommendation) 1
   • URS has lower likelihood of requiring repeat procedures 1

2. Lower pole stones ≤10 mm:

   • Either SWL or URS (strong recommendation) 1, 2

3. Total stone burden >20 mm:

   • First-line: PCNL (strong recommendation) 1, 2
   • SWL should NOT be offered as first-line therapy 1
   • For stones 20-40 mm: Staged flexible URS may be a practical option 3
   • For stones >40 mm: Miniaturized PCNL combined with flexible URS is preferred 3

4. Multiple stones:

   • For total burden <20 mm: URS is favorable (high stone-free rate after single session)
   • For total burden ≥20 mm: Staged operations should be considered 3

Special Considerations

• Infection stones: Complete stone removal plus eradication of UTI is essential 4

  • These stones are typically composed of magnesium ammonium phosphate, carbonate apatite, and monoammonium urate
  • Risk factors include urinary tract obstruction, neurogenic bladder, and indwelling catheters

• Stone density and location impact:

  • Lower calyx stones may negatively affect URS results
  • Multiple calyceal stones may negatively affect mini-PCNL outcomes
  • Stones with <677 Hounsfield units may have lower success rates with mini-PCNL 5

• For negligible kidney function: Nephrectomy may be considered 1

Post-Procedure Care

• Alpha-blockers and anti-muscarinic therapy may reduce stent discomfort 1
• Confirm stone clearance with follow-up imaging (ultrasound or KUB radiography) 2
• Increase fluid intake to >2L/day to prevent recurrence 2, 6
• Follow-up within 1-2 weeks with imaging to assess stone position and progression 2

Potential Complications and Pitfalls

• Ureteral injury risk:

  • URS: 3-6% risk of ureteral injury
  • SWL: 1-2% risk of ureteral injury 2

• Infection risk:

  • Administer antimicrobial prophylaxis prior to stone intervention based on prior urine culture results 2
  • Monitor for signs of infection (fever, flank pain) post-procedure

• Stone analysis:

  • Always send stone material for analysis except in patients with multiple recurrent stones of documented similar composition 2
  • Most common stone types: calcium oxalate (61%), calcium phosphate (15%), and uric acid (12%) 6

By selecting the appropriate procedure based on stone characteristics, patient factors, and available expertise, optimal outcomes can be achieved in the management of kidney stones.