When do you refer a patient with kidney stones to a specialist?

When to Refer Patients with Kidney Stones

Patients with recurrent or extensive nephrolithiasis should be referred to a specialist for evaluation and management to reduce morbidity and mortality associated with kidney stone disease. 1

Indications for Specialist Referral

Urgent/Emergency Referral

• Obstructing stones with suspected infection - This requires urgent drainage of the collecting system with a stent or nephrostomy tube 1
• Acute kidney injury (AKI) or abrupt sustained fall in GFR due to obstructing stones 1
• Severe pain uncontrolled with oral analgesics 2
• High-grade obstruction requiring hospitalization 2

Non-Urgent Referral to Urology

1. Stone characteristics:

   • Stone size >20 mm (requires PCNL as first-line therapy) 1
   • Complex stones (multiple or staghorn calculi)
   • Stones that fail to pass spontaneously after 4-6 weeks
   • Stones unlikely to pass with conservative management

2. Patient factors:

   • Failed medical expulsive therapy
   • Anatomical abnormalities of the urinary tract
   • Solitary kidney with stone burden
   • Occupational constraints (pilots, travelers) requiring definitive treatment

3. Treatment considerations:

   • When SWL and/or URS have failed or are unlikely to succeed 1
   • Need for surgical intervention (PCNL, laparoscopic, open, or robotic-assisted stone removal)

Referral to Nephrology

1. Metabolic abnormalities:

   • Persistent abnormalities of serum potassium 1
   • Hereditary kidney disease 1
   • Suspected metabolic stone disease requiring specialized evaluation

2. Kidney function concerns:

   • GFR <30 ml/min/1.73 m² (CKD stages G4-G5) 1
   • Significant albuminuria (ACR ≥300 mg/g or equivalent) 1
   • Progression of CKD associated with stone disease 1

Management Algorithm Based on Stone Size and Location

Small Renal Stones (≤10 mm)

• Symptomatic stones: Consider referral for URS as it leads to symptom resolution in 85-100% of patients 3
• Asymptomatic stones: Observation with increased fluid intake may be appropriate

Medium-Sized Renal Stones (10-20 mm)

• Non-lower pole stones: Refer for SWL or URS (stone-free rates: 77.2% for SWL, 86.1% for URS) 4
• Lower pole stones: URS generally preferred due to better clearance rates

Large Renal Stones (>20 mm)

• Refer to urology for PCNL as first-line therapy (do not offer SWL) 1
• Stone-free rates are higher with PCNL (94%) compared to URS (75%) for stones >20 mm 1

Special Considerations

Pediatric Patients

• Lower threshold for referral due to higher prevalence of metabolic abnormalities (present in ~30% of cases) 5
• Genetic factors play a significant role in pediatric stone disease 5

Patients with Diabetes or CKD

• More aggressive referral approach due to higher risk of complications
• Consultation with nephrology when stage 4 CKD develops has been found to reduce cost, improve quality of care, and delay dialysis 1

Common Pitfalls to Avoid

1. Delaying referral for obstructing stones with infection (urologic emergency)
2. Overreliance on SWL for stones >20 mm (poor success rates)
3. Failure to evaluate for metabolic causes in recurrent stone formers
4. Not considering kidney function when evaluating patients with stones
5. Missing anatomical abnormalities that may contribute to stone formation

By following these guidelines for timely referral, clinicians can help reduce the morbidity associated with kidney stone disease and improve patient outcomes through appropriate specialist intervention.