What is the treatment approach for patients with renal brushite stones?

Treatment Approach for Renal Brushite Stones

For patients with brushite stones, treatment should focus on increasing fluid intake, dietary modifications, and pharmacological therapy with potassium citrate and thiazide diuretics to address the common metabolic abnormalities of hypercalciuria, elevated urine pH, and hypocitraturia. 1, 2

Metabolic Profile of Brushite Stone Formers

• Brushite stone formers almost universally present with underlying metabolic abnormalities that require targeted intervention 2
• The most common metabolic abnormalities include:
  • Hypercalciuria (80-85% of patients) 2, 3
  • Elevated urine pH (>6.2) in approximately 60% of patients 2, 3
  • Low urine volume (<2L/day) in about 57% of patients 2
  • Hypocitraturia in 45-47% of patients 2
  • Distal renal tubular acidosis in up to 50% of patients 3

First-Line Treatment Approach

Increased Fluid Intake

• Increase fluid intake to achieve urine output of at least 2.5 liters daily 1, 4
• This is the most economical and fundamental preventive measure for all stone types 4

Dietary Modifications

• Moderate dietary salt restriction to limit urinary calcium excretion 5
• Normal to high calcium intake (800-1200 mg/day) rather than calcium restriction 5
• Low-normal protein intake to decrease calciuria 5
• Increased intake of fruits and vegetables (excluding high-oxalate varieties) to increase citrate excretion 5

Pharmacological Therapy

Potassium Citrate

• First-line pharmacological therapy for brushite stone formers with hypocitraturia or elevated urine pH 6
• Potassium citrate is a potent inhibitor of calcium phosphate crystallization 6
• Preferred over sodium citrate as the sodium load in the latter may increase urine calcium excretion 6

Thiazide Diuretics

• Should be offered to brushite stone formers with hypercalciuria 6
• Thiazides lower urinary calcium excretion and may increase the safety and efficacy of citrate therapy 6
• Can be used in combination with potassium citrate for patients with persistent stone formation 6

Monitoring and Follow-up

• Obtain a 24-hour urine specimen within six months of initiating treatment to assess response to therapy 6
• After initial follow-up, obtain a 24-hour urine specimen annually or more frequently depending on stone activity 6
• Monitor for recurrent stone events, which occur in approximately 38% of brushite stone formers at a mean of 33 months from treatment 2

Special Considerations

• Brushite stones are resistant to shock wave and ultrasonic lithotripsy, often requiring ballistic fragmentation for treatment 7
• There is an association between brushite stone disease and prior shock wave lithotripsy (SWL) treatment, with approximately 78% of brushite stone formers having received prior SWL 7, 2
• Some evidence suggests brushite stone formers may have started as calcium oxalate stone formers who sustained nephron injury (possibly from SWL) 7
• Patients with brushite stones often present with bilateral calculi (34%) and sizeable stone burden 2

Common Pitfalls to Avoid

• Neglecting to perform 24-hour urine studies in brushite stone formers 2
• Calcium restriction, which is not recommended and may worsen stone disease 5
• Inadequate follow-up, as brushite stone formers have high recurrence rates 2
• Failure to address all identified metabolic abnormalities 3, 2