Primary prevention

Fluid intake should be at least 2.5 to 3 litres per day for adults, and 1 to 2 litres a day for children and young people (depending on age) to prevent stone formation.[16][43][44]​ Dietary factors are also important.[45] Measures should include decreasing dietary fat, animal protein content, and sodium intake.[16][19][37][38][39][40][45][46][47]​ Achieving and maintaining a healthy body mass index (BMI) is also recommended.[47]

Secondary prevention

Long-term dietary and lifestyle modification is essential for preventing future calculi.

  • Diet should be balanced with contributions from all food groups, without excesses of any kind.[45][47]

Advise the patient (and their family or carers, as appropriate) to:

  • Drink 2.5 to 3 litres (adults) or 1 to 2 litres (children) of water each day[16][43][44]

    • In patients who are known stone formers, a target urine output of 2 to 2.5 litres per day is recommended; intake volume may need to be up to 4 litres per day to achieve this.[71][72][73]

  • Add fresh lemon juice to drinking water[16]

    • Lemon juice is high in citrate leading to higher urinary citrate, which may stop calcium from binding to other stone constituents, therefore preventing stone formation and recurrence.[16]

  • Not restrict calcium intake and maintain a normal calcium intake of 700-1200 mg/day for adults, and 350-1000 mg/day for children and young people (depending on age)[16]

    • The patient should only restrict their calcium intake if there are very strong reasons to do so.

    • This is to help prevent stone recurrence.[16] Dietary calcium restriction can lead to less binding of calcium to oxalate in the gastrointestinal tract, promoting hyperoxaluria and potentiating the risk for stone formation; furthermore, it could have detrimental effects on bone health.

  • Consume no more than 6 g of salt per day (adults) or 2-6 g of salt per day (children and young people, depending on age)[16]

    • A high consumption of sodium causes hypercalciuria by reduced proximal tubular re-absorption 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.

  • Eat plenty of fruits, vegetables, and fibre.[47]

    • Fruit and vegetable intake should be encouraged because of the beneficial effects of fibre.

    • The alkaline content of a vegetarian diet also gives rise to a desirable increase in urinary pH.

Encourage the patient to establish a healthy lifestyle, including physical activity habits, to achieve and maintain a healthy weight.[74]

Additional dietary advice may be given for specific patient groups (based on the types of stones they form) in a specialist metabolic clinic setting.

Where specific metabolic abnormalities exist, individualised preventative therapies may be required in addition to dietary modification.[47][71][116] These patients will need to be managed in a specialist metabolic clinic setting where they can be offered tailored advice and interventions. These abnormalities and recommended interventions include:

  • Uric acid stones: urinary alkalinisation with potassium citrate or sodium bicarbonate[47]

  • Hypercalciuria and recurrent stones that are more than 50% calcium oxalate: thiazide diuretic or potassium citrate (after the patient has restricted their sodium intake to no more than 6 g per day)[16]

  • Hypocitraturia and recurrent stones that are more than 50% calcium oxalate: urinary alkalinisation (e.g., potassium citrate); sodium bicarbonate or sodium citrate can be considered if the patient is at risk for hyperkalaemia[116]

  • Hyperoxaluria: oxalate chelator (e.g., calcium, magnesium, or colestyramine), potassium citrate, pyridoxine; a rare condition

  • Cystinuria: high fluid intake alongside urinary alkalinisation with potassium citrate, thiol binding agent (e.g., tiopronin which is tolerated better than d-penicillamine); a genetic abnormality requiring life-long management.[3]

Most of these strategies are applied to children with nephrolithiasis, although there are a limited number of well-designed trials in this age group.[117][118]

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