What is the size of ureteric calculi (kidney stones) that typically requires surgical intervention?

Size of Ureteric Calculi Requiring Surgical Intervention

Ureteric stones larger than 10 mm typically require surgical intervention, while stones smaller than 10 mm can often be managed conservatively with observation and medical expulsive therapy. 1

Management Algorithm Based on Stone Size

Stones <10 mm:

• Initial management should be observation with periodic evaluation for patients with controlled symptoms 1, 2
• Medical expulsive therapy (MET) using alpha-blockers significantly improves stone-free rates for distal ureteral stones <10 mm (77.3% vs 54.4% without treatment) 2
• Spontaneous passage rates are high:
  • Stones ≤5 mm: 92% chance of spontaneous passage 3
  • Stones <4 mm: Even higher probability of spontaneous passage, especially with medical assistance 2, 4

Stones >10 mm:

• Surgical intervention is recommended in most cases 1
• Only 28% chance of spontaneous passage for stones ≥6 mm 3
• For stones >10 mm, surgical options should be discussed with the patient 1

Surgical Options for Stones >10 mm

First-line treatment options:

• Both shock wave lithotripsy (SWL) and ureteroscopy (URS) are acceptable first-line treatments 1
• URS yields significantly greater stone-free rates for most stone stratifications 1
• URS has a better chance of achieving stone-free status with a single procedure but has higher complication rates 1

Considerations for surgical approach:

• Location of stone affects treatment success:
  • Proximal ureteral stones: 97% clearance rate with URS 5
  • Distal ureteral stones: High success rates with both SWL and URS 1
• For large stones (>20 mm), staged procedures may be necessary 5

Follow-up and Monitoring

• Patients should be followed with periodic imaging studies to monitor stone position and assess for hydronephrosis 1, 2
• Maximum duration for conservative therapy should be limited to 4-6 weeks to avoid kidney injury 2
• For stones 2-4 mm, 95% will pass spontaneously but may take up to 40 days 4
• For stones 4-6 mm, passage may take up to 39 days 4

Special Considerations

• Urine culture should be performed prior to any intervention to rule out infection 2
• Blind basketing (stone extraction without endoscopic visualization) should never be performed due to risk of ureteral injury 1, 2
• Patient factors such as previous stone experience and treatment significantly affect treatment choice 6
• In pediatric patients with ureteral stones <10 mm, both SWL (87%) and URS (95%) have high stone-free rates 1

Complications of Treatment

• URS complications include:

  • Ureteral injury: 3-6% depending on stone location 1
  • Stricture: 1-4% depending on stone location 1
  • Sepsis: 2-4% depending on stone location 1

• SWL complications include:

  • Steinstrasse (stone street): 4-8% depending on stone location 1
  • Sepsis: 3-5% depending on stone location 1
  • UTI: 4-6% depending on stone location 1

The decision between observation and surgical intervention should be based on stone size, location, symptom control, and patient preference, with 10 mm being the key threshold for considering surgical management 1, 2.