What are the European Association of Urology (EAU) guidelines for managing recurrent stone formers?

EAU Guidelines for Management of Recurrent Stone Formers

The European Association of Urology (EAU) guidelines recommend a comprehensive metabolic evaluation and targeted therapy based on specific stone composition and risk factors for all recurrent stone formers to reduce morbidity and prevent stone recurrence.

Evaluation of Recurrent Stone Formers

• A detailed medical and dietary history, serum chemistries, and urinalysis should be performed on all patients with recurrent kidney stones 1
• Complete metabolic evaluation should include one or two 24-hour urine collections analyzed for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 2
• Stone analysis should be performed whenever possible, especially in patients not responding to treatment, as changes in stone composition may occur over time 1, 2

General Dietary Recommendations

• Increased fluid intake to achieve urine volume of at least 2.5 liters daily is critical for all recurrent stone formers 2, 3
• Sodium intake should be limited to 2,300 mg (100 mEq) daily to reduce urinary calcium excretion 2
• Normal dietary calcium intake of 1,000-1,200 mg per day should be maintained, as dietary calcium restriction can paradoxically increase stone risk 2
• Calcium should be consumed primarily with meals to bind dietary oxalate in the gut 2

Pharmacological Management Based on Stone Type

Calcium Stones

• Thiazide diuretics are first-line therapy for patients with hypercalciuria and recurrent calcium stones 1, 2

  • Potassium supplementation may be needed to prevent hypokalemia 1, 2
  • Periodic blood testing is required to monitor for adverse effects including hypokalemia, hyperglycemia, and hyperlipidemia 1, 2

• Potassium citrate therapy should be offered to patients with:

  • Low or relatively low urinary citrate 1, 3
  • Normal citrate but low urinary pH 1, 3
  • Calcium phosphate stones with hypocitraturia 1, 3
  • Potassium citrate is preferred over sodium citrate, as sodium load increases urine calcium excretion 1, 3

• Allopurinol should be offered to patients with recurrent calcium oxalate stones who have hyperuricosuria (>800 mg/day) and normal urinary calcium 1

  • Hyperuricemia is not a required criterion for allopurinol therapy 1

Uric Acid Stones

• Potassium citrate is first-line therapy to increase urinary pH to approximately 6.0 1
• Allopurinol should not be routinely offered as first-line therapy, as most uric acid stones form due to low urinary pH rather than hyperuricosuria 1

Cystine Stones

• First-line therapy includes increased fluid intake, restriction of sodium and protein intake, and urinary alkalinization 1
• Potassium citrate should be used to raise urinary pH to approximately 7.0 1
• Cystine-binding thiol drugs (tiopronin) should be offered to patients unresponsive to dietary modifications and urinary alkalinization, or those with large recurrent stone burdens 1
  • Tiopronin is preferred over d-penicillamine due to better efficacy and fewer adverse events 1

Struvite Stones

• Aggressive medical approach is required due to high risk for recurrence 1
• Patients should be monitored for reinfection with urease-producing organisms 1
• Urease inhibitors may be beneficial despite extensive side effect profiles 1

Follow-up and Monitoring

• A 24-hour urine specimen should be obtained within six months of initiating treatment to assess response to dietary and/or medical therapy 1
• After initial follow-up, annual 24-hour urine specimens should be obtained to assess patient adherence and metabolic response 1
• Periodic blood testing is necessary to monitor for adverse effects of pharmacological therapy 1
• If patients remain stone-free for an extended period on their treatment regimen, discontinuation of follow-up testing may be considered 1

Pitfalls and Caveats

• Sodium citrate preparations should be avoided in favor of potassium citrate, as sodium load may increase urinary calcium excretion 2, 3
• Lower doses of thiazides may have fewer adverse effects but potentially less efficacy for stone prevention 2
• Repeat stone analysis is essential when patients do not respond to treatment, as stone composition may change over time 1
• Calcium supplements should be avoided as they may increase stone risk, unlike dietary calcium 2