IntroductionEpidemiologyI. Epidemiology of kidney stonesI.1. Prevalence of kidney stonesI.2. An increasing trend in childrenPathophysiology II. Pathophysiology of kidney stonesII.1. LithogenesisII.1.1. Urine supersaturation : the driving force of crystallogenesisII.1.2. Promoters and inhibitors of stone formationII.2. Urine volume and composition: a necessary balanceRisk factorsIII. Risk factors for kidney stonesIII.1. Individual, non-modifiable risk factorsIII.1.1 Family historyIII.1.2. Race and ethnicityIII.1.3. Age and genderIII.1.4. Current change in gender prevalenceIII.2. Lifestyle related factorsIII.2.1. Calcium intakeIII.2.2. Emerging dietary risk factorsIII.2.3. Association with other chronic diseasesDehydrationIV. Dehydration: a risk factor for kidney stonesIV.1. Low urine volume: a key risk factor for kidney stonesIV.2. Environmental factors predisposing to low urine volumeIV.2.1. Occupational risk of kidney stonesIV.2.2. Climate and temperature as risk factorsWater & recurrenceV. Prevention of stone recurrence with high water intakeV.1. Reduction of recurrence rate with increased water intakeV.2. Water intake and urinary parameters in stone formersWater & incidenceVI. Primary prevention of stones with high water intakeVI.1. Reduction of stone incidence with increased water intakeVI.2. Water intake and urinary parameters in healthy subjectsWater & health costsVII. Water intake and health costs of kidney stonesVII.1. Reduction of stone recurrence costs via adequate water intakeVII.2. Reduction of first stone costs with adequate water intakeRecommendationsVIII. Dietary and water recommendations for stone preventionVIII.1. Guidelines for the prevention of recurrence in patientsVIII.2. Dietary and water guidelines for general populationConclusion References
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Kidney stone formation results from an imbalance in urine composition, which is influenced by food (total osmolar load and chemical composition) and water intakes. Hence, recommendations to prevent kidney stones recurrence mainly involve changes in dietary habits, changes in lifestyle and increased water intake. Depending on the composition of previous stone(s), dietary advice will vary and additional medication may be necessary for patients with a high risk profile. Overall, recommendations also include general preventive measures (e.g. diet, water intake), applicable to every type of stone former (Kairaitis 2007; Tiselius et al. 2001).
In Europe, guidelines for the management of stone patients were established by the European Association of Urology (EAU). Main general preventive measures of EAU guidelines are presented in Figure 9. They include recommendations related to fluid intake, diet and lifestyle. Dietary recommendations for the prevention of stone recurrence are based on guidelines for the general population: normal calcium intake (1,000-1,200mg/d), low intakes of sodium chloride (4-5g/d) and animal proteins (0.8-1g/kg/d). Recommendations on fluid intake for the prevention of recurrence are based on urine volume. The EAU recommends a fluid intake sufficient to achieve a urinary output of at least 2.0L per day. Lifestyle recommendations also stipulate that excessive fluid loss (e.g. sweating during exercise, diarrhea) should be compensated by an increased fluid intake. (Tiselius et al. 2001).
Figure 9. General measures for the prevention of kidney stone recurrence based on European Association of
Urology guidelines for nephrolithiasis patients.
(Adapted from Tiselius et al. 2001).
In Australia, the organization Caring for Australasians with Renal Impairment (CARI) established guidelines for recurrent calcium stone formers. They also recommend a normal calcium intake (1,000-1,200mg/d), and a fluid intake sufficient to achieve a urine volume of at least 2.0L per day (Kairaitis 2007).
Dietary guidelines for recurrent kidney stones patients are based on guidelines for the general population and both are thus similar. Recommended intakes are 1.000-1.200mg/d for calcium, 5g/d for sodium and 0.83g/ kg/d for protein (Ross et al. 2011; World Health Organization 2007; World Health Organization 2012).
Recommendations for water intake in the general population vary between countries. Official guidelines for Europe are presented in Table 1. Even though most of these recommendations may be sufficient to achieve a urine volume of at least 2L/d and may thus be similar to recommendations for the prevention of recurrence, they are not based on urinary outputs. They actually state adequate values for Total Water Intake (TWI) which includes both water coming from food and water coming from beverages.
Table 1. Recommendations for Total Water Intake (TWI) in Europe.
EFSA estimated that around 80% of TWI comes from fluids, and 20% from food (EFSA 2010). This is equivalent to drinking 1.6L/d of water for adult women, 2L/d for adult men, 1.8L/d for pregnant women and 2.2L/d for lactating women.
Take home messages
Dietary recommendations are similar in recurrent stone formers and in the general population. They include a normal calcium intake, limited salt and animal protein intakes, and a high water intake. In case of large water losses it is recommended to increase water intake.