Treatment of Crystals in Urine
The first-line treatment for urinary crystals is increasing fluid intake to achieve at least 2 liters of urine output daily, with pharmacologic therapy (thiazide diuretics, potassium citrate, or allopurinol) reserved for patients who fail conservative management after 6 months. 1, 2
Initial Management: Hydration
- Increase fluid intake to produce at least 2 liters of urine per day as the cornerstone of therapy for all crystal types 1, 2
- Distribute fluid intake throughout the day and night to maintain consistent urine dilution 2
- Higher volumes (2.5-3 liters) may be needed depending on crystal type and severity 2
- Obtain a 24-hour urine collection within 6 months to assess metabolic risk factors and response to hydration therapy 1, 2
Crystal Type-Specific Treatment
Calcium Oxalate/Calcium Phosphate Crystals
- Do not restrict dietary calcium, as this paradoxically increases oxalate absorption and stone risk 2
- Reduce sodium intake to <2,300 mg/day and limit animal protein consumption 1
- If hypocitraturia is present, offer potassium citrate therapy to increase urinary citrate to normal levels (400-700 mg/day) 1, 3
- For hypercalciuria, consider thiazide diuretics (hydrochlorothiazide 50 mg daily or chlorthalidone 25-50 mg daily) 1, 2
- For hyperuricosuria with normal urinary calcium, offer allopurinol (urinary uric acid >800 mg/day) 1
Uric Acid Crystals
- First-line therapy is urinary alkalinization with potassium citrate to achieve pH 6.0-7.0, not allopurinol 1, 2
- Most patients have low urinary pH rather than hyperuricosuria as the predominant risk factor 1
- Decrease consumption of meat, chicken, and seafood to reduce purine intake 1
- Consider allopurinol only if documented hyperuricosuria is present 2
Cystine Crystals
- Aggressive hydration (4 liters oral intake daily) plus urinary alkalinization to pH 7.0-7.5 is mandatory 2
- Restrict sodium to ≤2,300 mg/day and limit animal protein intake 1, 2
- If refractory to hydration and alkalinization, offer tiopronin as first-line thiol agent (preferred over d-penicillamine due to fewer adverse events) 1
Struvite/Triple Phosphate Crystals
- Urine culture and antibiotic therapy targeting urease-producing organisms (particularly Proteus mirabilis) are required 2, 4
- Complete stone removal is essential to eradicate causative organisms and prevent recurrent infection 4
- Increase fluid intake to at least 2.5 liters of urine output daily 4
Pharmacologic Therapy Algorithm
If increased fluid intake fails to reduce crystal formation after 6 months, initiate pharmacologic monotherapy based on the following hierarchy: 1, 2
- For calcium stones with hypocitraturia: Potassium citrate (sustained increase in urinary pH to ~6.5 and citrate to 400-700 mg/day) 1, 3
- For calcium stones with hypercalciuria: Thiazide diuretics at higher doses (hydrochlorothiazide 50 mg or chlorthalidone 25-50 mg) 1
- For calcium oxalate stones with hyperuricosuria and normocalciuria: Allopurinol 1
- For persistent calcium stones despite addressing metabolic abnormalities: Thiazide diuretics and/or potassium citrate 1
Important Caveats
- Potassium citrate is preferred over sodium citrate, as the sodium load may increase urine calcium excretion 1
- The evidence evaluated higher doses of thiazides; lower doses have fewer adverse effects but unknown efficacy for stone prevention 1
- Combination therapy with multiple agents is not more beneficial than monotherapy for calcium stones 1
- For calcium phosphate stone formers, be cautious with urinary alkalinization as increased pH can promote calcium phosphate crystal formation 1
Follow-Up Monitoring
- Obtain 24-hour urine collection within 6 months of initiating treatment to assess response 1, 2
- Monitor parameters including calcium, oxalate, citrate, uric acid, cystine (if indicated), and volume 2
- For high-risk patients, more frequent monitoring every 3-4 months is appropriate 2