EAU Guidelines for Metabolic Evaluation of Recurrent Stone Formers
The European Association of Urology (EAU) strongly recommends performing a detailed metabolic evaluation for all recurrent stone formers, including medical history, serum chemistries, urinalysis, and 24-hour urine collections to identify specific risk factors and guide targeted treatment. 1
Initial Evaluation Components
- Obtain a detailed medical and dietary history, serum chemistries, and urinalysis for all stone formers (EAU: Strong recommendation) 1
- Perform stone analysis at least once when available to guide preventive measures (EAU: Strong recommendation) 1
- Review imaging studies to quantify stone burden and identify high-risk features such as bilateral stones or nephrocalcinosis 1
- Conduct metabolic testing with 24-hour urine collections for recurrent stone formers (EAU: Strong recommendation) 1
- Analyze 24-hour urine for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 1
- Test for urinary cystine in patients with suspected cystinuria or family history of cystine stones 1
- Consider genetic testing for patients with early-onset stone disease (≤25 years), recurrent stones (≥2 episodes), bilateral disease, or strong family history 1
Risk Stratification
The EAU categorizes stone formers based on risk of recurrence:
- High-risk factors include recurrent stone formation, family history, and specific stone compositions (uric acid, cystine, infection stones) 1
- Stone history (recurrence patterns, regrowth, past surgeries) is critical for risk assessment 1
- Approximately 50% of recurrent stone-formers experience only one recurrence, while 10% have highly recurrent disease 1
Dietary Management Recommendations
- Increase fluid intake to achieve urine volume of at least 2.5 liters daily (EAU: Strong recommendation) 1
- Limit sodium intake to 3,000-5,000 mg daily (EAU: Strong recommendation) 1
- Maintain normal dietary calcium intake of 1,000-1,200 mg per day 1, 2
- For cystine stone formers, increase fluid intake to achieve urine output of at least 3L (EAU: Strong recommendation) 1
Pharmacological Management by Stone Type
Calcium Oxalate Stones
- For hypercalciuric patients: thiazide diuretics (EAU: Strong recommendation) 1
- For hypocitraturic patients: alkali citrate or sodium bicarbonate (EAU: Strong recommendation) 1
- For hyperuricosuric patients: allopurinol as first-line (EAU: Strong recommendation) or febuxostat as second-line (EAU: Strong recommendation) 1
Calcium Phosphate Stones
- For hypercalciuric patients: thiazide diuretics (EAU: Strong recommendation) 1
- For patients with high urinary pH: L-Methionine to acidify urine (EAU: Weak recommendation) 1
Uric Acid Stones
- Urinary alkalization with alkaline citrates or sodium bicarbonate to achieve pH 6.2-6.8 (EAU: Strong recommendation) 1
- Allopurinol as first-line treatment in the presence of hyperuricosuria (EAU: Strong recommendation) 1
Cystine Stones
- Urinary alkalization to achieve pH 7.0-7.5 (EAU: Strong recommendation) 1
- If refractory to alkalization, thiol binding agents (EAU: Strong recommendation) 1
Follow-up Monitoring
- Obtain follow-up 24-hour urine collections within 8-12 weeks after initiating therapy to assess response (EAU recommendation) 1
- Monitor for adverse effects of medications with periodic blood tests 1
- Continue long-term follow-up for recurrent stone formers to ensure treatment efficacy 1
Common Pitfalls and Caveats
- Failure to perform comprehensive metabolic evaluation in recurrent stone formers leads to missed opportunities for targeted prevention 1
- Inadequate fluid intake remains the most common modifiable risk factor for stone recurrence 1, 2
- Non-adherence to dietary sodium restriction can undermine the efficacy of thiazide therapy for hypercalciuria 1
- Genetic causes of stone disease are often overlooked but should be considered in early-onset or severe recurrent cases 1
- The EAU guidelines differ from AUA guidelines in recommending allopurinol as first-line therapy for uric acid stone formers with hyperuricosuria 1