Table 2.

Therapeutic approach to calcium phosphate stone formers

Steps 1–3 Might Be Instituted Sequentially or Simultaneously Depending on Stone Activity and Patient Preferences
1. Fluid therapy
 increase fluid intake up to 3 L or more to ensure urine output ≥2.5 L/d
  instruction: 3 L is approximately 100 oz or 12 × 8-oz servings
 measure 24-h urine output periodically (patient can do this measurement at home)
 higher fluid intake should be consistent throughout the day
 increase fluid intake with exercise
 increase fluid intake with meals
 increase fluid intake before bedtime but minimize disturbance of sleep
 most fluid intake should be water
  avoid grapefruit juice (associated with more stones)
  limit cola (may have adverse effects on urine chemistry)
2. Dietary therapy
 prescribe diet based on 24-h urine data but educate patient about general principles
 limit sodium intake to 2 g (about 100 meq) per day
 limit oxalate intake if calcium oxalate is an important stone component
  reduce intake of high oxalate foods but avoid quantitative targets (https://regepi.bwh.harvard.edu/health/oxalate/files)
  accompany ingested oxalate with ample fluids
  accompany ingested oxalate with dairy products
 moderate protein intake (e.g., 1.2 g/kg per day)
  two to three servings of dairy per day may be desirable (if calcium oxalate is a stone component)
3. Pharmacologic therapy
 judge efficacy based on results of 24-h urine collections
 Potassium citrate 20–30 meq two times per day
  one dose at bedtime to cover lower urine volume and higher calcium concentrations
  benefit is uncertain if
   urine volume does not increase
   urine calcium does not fall
   urine citrate does not rise
   urine pH rises
 Thiazides
 may be useful even if hypercalciuria is not present
  chlorthalidone 12.5–50 mg one time per day
  hydrochlorothiazide 25–50 mg one or two times per day
  indapamide 2.5–5.0 mg one time per day
 maintain normal serum potassium concentration with potassium citrate if hypocitraturia is present or potassium chloride if hypocitraturia is not present
 if necessary, consider amiloride 5–10 mg two times per day, spironolactone 25 mg two times per day, or eplerenone 25–50 mg one time per day
  avoid poorly soluble triamterene