How to manage non-obstructing kidney stones?

Management of Non-Obstructing Kidney Stones

Active surveillance is the recommended first-line approach for most asymptomatic non-obstructing kidney stones, as the majority remain asymptomatic over time with less than 30% causing symptoms through an average follow-up of more than 3 years. 1

Assessment and Risk Stratification

When evaluating non-obstructing kidney stones, consider:

• Stone size and location
• Presence of symptoms
• Stone composition (if known)
• Anatomical abnormalities
• Risk factors for progression

Risk Factors for Intervention

Several factors increase the likelihood that a non-obstructing stone will require intervention:

• Stone size >7 mm 2
• Upper/mid renal location (more likely to become symptomatic than lower pole) 1
• Stones composed of struvite or cystine 2
• Concurrent renal anatomical abnormalities 2

Management Algorithm

1. Asymptomatic Non-Obstructing Stones

For most asymptomatic non-obstructing kidney stones:

• Active surveillance is appropriate and durable
  • No correlation between longer surveillance duration and increased intervention rates 3
  • Only 28% of stones cause symptoms during follow-up (average 41 months) 1
  • Only 20% require surgical intervention for pain 1

Surveillance Protocol:

• Regular imaging follow-up (ultrasound or KUB x-ray) every 6-12 months 4
• More frequent monitoring for high-risk stones (>7 mm, struvite/cystine composition)
• Patient education about symptoms requiring urgent evaluation

2. Specific Stone Scenarios

Lower Pole Stones ≤10 mm

• First-line: Active surveillance (lower pole stones are less likely to cause symptoms or pass spontaneously) 1
• If symptomatic: Offer SWL or URS (strong recommendation) 5

Lower Pole Stones >10 mm

• Do not offer SWL as first-line therapy (strong recommendation) 5
• Consider URS or PCNL based on stone characteristics and patient factors

Small Volume Staghorn Calculi

• SWL monotherapy may be considered in select cases with normal collecting system anatomy 5
• Most staghorn calculi require more aggressive management

3. Symptomatic Non-Obstructing Stones

Even small non-obstructing calyceal stones (≤4 mm) can cause pain without obstruction ("small stone syndrome") 6:

• Consider intervention if pain persists despite conservative management
• Ureteroscopic treatment can achieve complete or partial pain resolution in these cases 6

Intervention Options

When intervention becomes necessary:

1. Shock Wave Lithotripsy (SWL)

   • Lowest morbidity and complication rate 5
   • Lower stone-free rate in a single procedure compared to URS 5
   • Not recommended as first-line for lower pole stones >10 mm 5

2. Ureteroscopy (URS)

   • Higher stone-free rate in a single procedure (90% vs 72% for SWL) 5
   • May require staged procedures for large stone volumes 5
   • Recommended for suspected cystine or uric acid stones 5

3. Percutaneous Nephrolithotomy (PCNL)

   • Reserved for larger stone burdens (>20 mm) 5
   • Flexible nephroscopy should be a routine part of standard PCNL 5
   • Tubeless PCNL is an option for uncomplicated cases 5

Follow-up and Prevention

• Increase fluid intake to >2L/day 4
• Consider metabolic evaluation to prevent recurrence 4
• Regular follow-up imaging to monitor stone position and growth 4
• Evaluate for predisposing factors including congenital abnormalities, metabolic disorders, and recurrent UTIs 4

Important Caveats

• Silent Hydronephrosis: About 3% of asymptomatic stones may cause painless obstruction requiring intervention 1
• Stone Growth: Regular imaging is essential as growth may occur without symptoms
• Uric Acid Stones: Consider oral chemolysis (success rate ~80%) 4
• Normal Saline Irrigation: Must be used for PCNL and URS procedures to avoid electrolyte abnormalities 5