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Medical Nutrition Therapy for Pediatric Kidney Stone Prevention, Part One

      Intended Audience: Pediatrics; Nephrology Outpatient Clinic; Children With Kidney Stones

      Renal stone disease, or nephrolithiasis, is a major health concern associated with significant pain, morbidity, and medical cost. Recurrent nephrolithiasis can lead to chronic kidney disease, as well as increased risk of related conditions such as cardiovascular disease and fracture.
      • Sigurjonsdottir V.K.
      • Runolfsdottir H.L.
      • Indridason O.S.
      • Palsson R.
      • Edvardsson V.O.
      Impact of nephrolithiasis on kidney function.
      The incidence of nephrolithiasis appears to be increasing among US children in recent decades. Moreover, the health and economic burden of nephrolithiasis may be heightened in children who have increased rates of metabolic abnormalities, resulting in recurrent nephrolithiasis, leading to increased risk for developing end-stage renal disease.
      • Edvardsson V.O.
      • Goldfarb D.S.
      • Lieske J.C.
      • et al.
      Hereditary causes of kidney stones and chronic kidney disease.
      The majority of children (up to 95%) with nephrolithiasis have at least one metabolic abnormality that will likely require a combination of dietary and pharmacological therapy. Most common metabolic abnormalities are hypercalciuria and hypocitraturia, either isolated or co-occurring; other metabolic abnormalities include hyperuricosuria, hyperoxaluria, and cystinuria.
      • Spivacow F.R.
      • Negri A.L.
      • del Valle E.E.
      • Calvino I.
      • Fradinger E.
      • Zanchetta J.R.
      Metabolic risk factors in children with kidney stone disease.
      • Bastug F.
      • Dusunsel R.
      Pediatric urolithiasis: causative factors, diagnosis and medical management.
      • Dwyer M.E.
      • Krambeck A.E.
      • Bergstralh E.J.
      • Milliner D.S.
      • Lieske J.C.
      • Rule A.D.
      Temporal trends in incidence of kidney stones among children: a 25-year population based study.
      Although studies that focus on pediatric populations are scarce, extrapolations from adult research suggest that the increasing rates of nephrolithiasis are related to shifting dietary norms, such as the widespread consumption of processed and fast foods, diets high in sodium and animal protein, and the decline in the consumption of fruits, vegetables, and calcium-rich foods.
      • Bastug F.
      • Dusunsel R.
      Pediatric urolithiasis: causative factors, diagnosis and medical management.
      • Dwyer M.E.
      • Krambeck A.E.
      • Bergstralh E.J.
      • Milliner D.S.
      • Lieske J.C.
      • Rule A.D.
      Temporal trends in incidence of kidney stones among children: a 25-year population based study.
      • Sas D.J.
      • Hulsey T.C.
      • Shatat I.F.
      • Orak J.K.
      Increasing incidence of kidney stones in children evaluated in the emergency department.
      • Tasian G.E.
      • Ross M.E.
      • Song L.
      • et al.
      Annual incidence of nephrolithiasis among children and adults in South Carolina from 1997 to 2012.
      • Routh J.C.
      • Graham D.A.
      • Nelson C.P.
      Epidemiological trends in pediatric urolithiasis at United States freestanding pediatric hospitals.
      Medical nutrition therapy aims to prevent recurrence, and as such, attenuate the burden of kidney stone disease in pediatric populations. Although the role of nutrition is increasingly appreciated, its therapeutic impact may be diminished due to a lack of teaching tools and resources designed to meet the specific needs of pediatric patients and their families. This introduction represents the first of a three-part series of handouts intended to provide a comprehensive nutrition education tool for the prevention of pediatric nephrolithiasis. The dietary recommendations presented below are relevant to most children with nephrolithiasis, regardless of metabolic abnormality.

      Increase Fluids

      Increased fluid intake is recommended for all children with nephrolithiasis, irrespective of stone type.
      • Valentini R.P.
      • Lakshmanan Y.
      Nephrolithiasis in children.
      Adequate hydration increases urine volume, which decreases the relative concentration of stone-forming substances and thereby prevents the supersaturation that can lead to crystallization. In general, fluid intake of 1.5 times ‘‘maintenance’’ fluids is used; this translates to approximately 3 liters (L) of fluid intake for a teenager with stone disease to maintain a daily urine output of at least 2 L.
      • Valentini R.P.
      • Lakshmanan Y.
      Nephrolithiasis in children.
      Likewise, urine output goals are >750 mL for infants, >1,000 mL for children 1–4 years in age, and >1,500 mL for children 5-10 years of age.
      • Bastug F.
      • Dusunsel R.
      Pediatric urolithiasis: causative factors, diagnosis and medical management.
      • Borghi L.
      • Meschi T.
      • Amato F.
      • Briganti A.
      • Novarini A.
      • Giannini A.
      Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study.
      An alternative way to calculate the amount of fluid required to account for the size of the child is to use body surface area and to use a minimum of 2 L/m2. Patients should increase fluid intake during hot weather or strenuous exercise.
      The type of beverage may also play a role; orange and lemon juices are beneficial because they increase urinary citrate, whereas sugar-sweetened beverages may increase risk of stone development.
      • Bastug F.
      • Dusunsel R.
      Pediatric urolithiasis: causative factors, diagnosis and medical management.
      • Tasian G.E.
      • Ross M.E.
      • Song L.
      • et al.
      Annual incidence of nephrolithiasis among children and adults in South Carolina from 1997 to 2012.
      • Curhan G.C.
      • Willett W.C.
      • Speizer F.E.
      • Spiegelman D.
      • Stampfer M.J.
      Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women.

      Limit Sodium

      Excessive dietary sodium can promote hypercalciuria or loss of calcium in the urine. Since calcium is a component of more than 80% of stones, minimizing calcium supersaturation is a reasonable prophylactic goal for overall stone prevention. A reduction in sodium is also recommended for cystine stones, as these patients are also at risk for subsequent calcium-stone formation.
      • Claes D.J.
      • Jackson E.
      Cystinuria: mechanisms and management.
      While arguably less important for uric acid and struvite stones, limiting excessive sodium intake is a sensible goal for all patients, especially considering the long-term risk of hypertension and stroke associated with nephrolithiasis.
      • Dwyer M.E.
      • Krambeck A.E.
      • Bergstralh E.J.
      • Milliner D.S.
      • Lieske J.C.
      • Rule A.D.
      Temporal trends in incidence of kidney stones among children: a 25-year population based study.
      • Tasian G.E.
      • Ross M.E.
      • Song L.
      • et al.
      Annual incidence of nephrolithiasis among children and adults in South Carolina from 1997 to 2012.
      • Evan A.P.
      Physiopathology and etiology of stone formation in the kidney and the urinary tract.
      • Lin S.Y.
      • Lin C.L.
      • Chang Y.J.
      • et al.
      Association Between Kidney Stones and Risk of Stroke: A Nationwide Population-Based Cohort Study.
      Daily sodium intake should not exceed the tolerable upper intake levels recommended by the Institute of Medicine: <1.5 g for children aged 1-3 years; <1.9 g for ages 4-8 years, <2.2 g for ages 9-13 years, and <2.3 g for ages 14-18 years.
      Institute of Medicine (U.S.)
      Panel on Dietary Reference Intakes for Electrolytes and Water. DRI, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate.

      Enjoy More Fruits and Vegetables

      Evidence from both observational and experimental studies suggest that diets high in fruits and vegetables, adequate in dairy products, and low in animal protein—such as the dietary approaches to stop hypertension eating plan—confer combined protective benefits. Fruits and vegetables alkalinize the urine, helping to prevent calcium oxalate, cystine, and uric acid stones. Nutrients such as potassium, calcium, and magnesium diminish intestinal absorption of oxalate. Finally, plant foods increase urinary citrate, an important inhibitor of stone crystallization.
      • Meschi T.
      • Maggiore U.
      • Fiaccadori E.
      • et al.
      The effect of fruits and vegetables on urinary stone risk factors.
      • Noori N.
      • Honarkar E.
      • Goldfarb D.S.
      • et al.
      Urinary lithogenic risk profile in recurrent stone formers with hyperoxaluria: a randomized controlled trial comparing DASH (Dietary Approaches to Stop Hypertension)-style and low-oxalate diets.

      Acknowledgments

      The authors would like to thank Ai Mitton for providing graphic design and creative input during the development of this patient education tool.

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