Primary prevention

Fluid intake should be at least 2.5 to 3.0 L per day for adults, and 1-2 L a day for children and young people (depending on age) to prevent stone formation.[15][16] Dietary factors are also important.[46] Measures should include decreasing dietary fat, animal protein intake, and sodium intake.[22][40][41][42][43][46][47][48] Achieving and maintaining a healthy body mass index (BMI) is also recommended.[48]

Secondary prevention

In patients that are known stone formers, a target urine output of 2.0 to 2.5 L per day is recommended; intake volume may need to be up to 4 L per day to achieve this.[17][18][19]​​ Long-term dietary modification is essential for preventing future calculi.[46] ​Orange juice is able to bring the urinary citrate levels up much more than lemon juice because of its high potassium content. 

Diet should be balanced with contributions from all food groups, without excesses of any kind.[48]

  • Fruits, vegetables, and fibers: fruit and vegetable intake should be encouraged because of the beneficial effects of fiber. The alkaline content of a vegetarian diet also gives rise to a desirable increase in urinary pH.

  • An excessive intake of oxalate-rich products should be limited or avoided to prevent an oxalate load. This includes fruit and vegetables rich in oxalate such as wheat bran. This is particularly important in patients in whom a high oxalate excretion has been demonstrated. The following products have a high content of oxalate:[160]

    • Rhubarb

    • Spinach

    • Chocolate

    • Tea

    • Nuts

    • Vitamin C is a precursor of oxalate; taking more than 1000 mg/day is not recommended.

  • Animal protein should be restricted.[17]​ An excessive consumption of animal protein may give rise to hypercalciuria, hypocitraturia, low pH, hyperoxaluria, and hyperuricosuria.

  • Calcium intake should not be restricted unless there are very strong reasons because of the inverse relationship between dietary calcium and calcium stone formation. The recommended calcium intake to prevent calcium stones is 1000-1200 mg per day (equivalent to 3 servings of dairy products with meals).[17][160]​ Calcium supplements are not recommended except in cases of enteric hyperoxaluria.

  • Avoid high salt intake.[160]​ A high consumption of sodium causes hypercalciuria by reduced proximal tubular reabsorption of calcium. Urinary citrate is reduced. The risk of forming sodium urate crystals is increased and the effect of thiazide in reducing urinary calcium is counteracted by a high sodium intake.

  • The intake of food particularly rich in urate should be restricted in patients with hyperuricosuric calcium oxalate stone disease, as well as in patients with uric acid stone disease. Examples of food rich in urate include:[160]

    • Red meat

    • Organ meat (liver, kidneys)

    • Sardines, anchovies, shellfish.

Where specific metabolic abnormalities exist and are not responsive to dietary modification, specific preventive therapies may be required.[17] These include:

  • Uric acid stones: urinary alkalinization with potassium citrate or sodium bicarbonate.

  • Hyperuricosuria, recurrent calcium oxalate stones, and normal urine calcium: allopurinol or febuxostat.

    • An increased risk of death has been reported with febuxostat compared with allopurinol.[139] Febuxostat should only be prescribed for patients who can not tolerate allopurinol or where treatment with allopurinol has failed, and who have been counseled regarding cardiovascular risk.[138] In July 2019, the UK Medicines and Healthcare products Regulatory Agency issued a reminder to avoid treatment with febuxostat in patients with preexisting major cardiovascular disease, unless no other therapy options are appropriate.[140]

  • Hypercalciuria and recurrent calcium stones: thiazide diuretic with or without potassium supplementation (potassium citrate)

  • Hypocitraturia and recurrent calcium stones: urinary alkalinization (e.g., potassium citrate; sodium bicarbonate can be considered if the patient is at risk for hyperkalemia)

  • Hyperoxaluria: oxalate chelator (e.g., calcium, magnesium, or cholestyramine), potassium citrate, pyridoxine

  • Cystinuria: urinary alkalinization with potassium citrate, thiol binding agent (e.g., tiopronin which is tolerated better than penicillamine)[2]

  • Struvite stones: vigilant monitoring and treatment for urinary tract infections with or without long term antibiotic prophylaxis. Urease inhibitors (e.g., acetohydroxamic acid), are best reserved for complex/recurrent struvite stones in which surgical management has been exhausted.[31] Secondary care supervision should be employed as it can produce severe adverse effects such as phlebitis and hypercoagulability.

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