Page 5 - CUA guideline on the evaluation and medical management of the kidney stone patient

Kidney stone guideline update

intake, this resulted in fewer stone episodes than a reduced calcium and oxalate excretion and resulted in normalization
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calcium diet. In a large prospective cohort of men, dietary of urine calcium excretion for one-third of patients. 82
protein was directly associated with the risk of stone for- Recommendation: Patients with recurrent calcium neph-
32
mation (RR 1.33). In a prospective trial of idiopathic cal- rolithiasis should aim for sodium intake of 1500 mg daily
cium stone-formers and controls, dietary records indicated and not exceed 2300 mg daily (Level I-2 evidence, Grade
increased consumption of protein (animal and vegetable) B Recommendation).
and purine-rich foods in stone-formers. Urinary oxalate and
calcium were higher and citrate lower in the stone-forming Fruits and vegetables
group, while uric acid was similar. Animal protein affected
urinary oxalate only minimally. In another study, calcium Low dietary intake of fiber, fruit, and vegetables increases
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and uric acid levels in urine were increased with dietary the risk of kidney stones in women. In another population-
intake of protein. 76 based study, high dietary fruit intake was shown to decrease
Other studies did not find a strong correlation between stone risk. In a small cohort of patients, eliminating fruits
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animal protein intake and risk of nephrolithiasis. Ninety-nine and vegetables from the diet resulted in decreased urine
patients with calcium oxalate stones were randomized to potassium, magnesium, citrate, and increased urine calcium.
low-protein, high-fiber diet vs. no intervention. All patients In 26 stone-forming patients with hypocitraturia, introduc-
were instructed to increase fluid intake and maintain a diet ing these foods resulted in increased excretion of citrate,
adequate in calcium. The patients in the low-protein, high- potassium, and magnesium and reduction in the saturation
fiber diet group had increased stone formation compared of calcium oxalate and calcium phosphate. 85
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to the control group. In other large dietary cohort studies, Recommendation: For kidney stone patients, a diet high
animal protein intake failed to demonstrate increased risk in fiber, fruits, and vegetables may offer a small protective
of stones in women. 31,34 effect against stone formation (Level of Evidence 2-3, Grade
A diet high in animal protein was found to be associ - C Recommendation).
ated with increased excretion of undissociated uric acid
due to a reduction in urinary pH, as well as a reduction in Vitamin C
citrate excretion, predisposing these individuals to uric acid
nephrolithiasis. A vegetarian diet has been demonstrated to In population-based studies, intake of over 1000 mg of vita-
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reduce the risk of uric acid crystallization by 93% compared min C daily caused a slight increase in the risk of neph -
to a typical Western diet. 79 rolithiasis. 50,59 Vitamin C supplementation of 1‒2 g was
Different types of animal protein were compared in a associated with increased urinary oxalate in stone-forming
randomized crossover study in 15 healthy volunteers using patients. 86,87 It is theorized that the excess vitamin C is con-
beef, chicken, and fish. Fish had high purine content and verted to oxalate.
resulted in increased urinary uric acid excretion. Beef intake Recommendation: Vitamin C supplementation of more
resulted in the highest saturation of calcium oxalate com- than 1000 mg daily is not recommended due to the asso-
pared to chicken, but was similar to fish. 80 ciated risk of hyperoxaluria and nephrolithiasis (Level
Recommendation: In patients with recurrent calcium Evidence 2-3, Grade C Recommendation).
oxalate and uric acid nephrolithiasis, moderation of animal
protein intake and avoidance of purine rich foods is sug- Specific prophylaxis based on stone composition
gested (Level of Evidence 2-3, Grade C Recommendation).
In the following section, “index patients” have been cre-
Sodium ated based on the predominant stone composition. Potential
metabolic abnormalities will be described and specific diet
When the urinary excretion levels of patients with idiopathic and medical interventions will be highlighted for each clini-
hypercalciuria were compared to those with normocalciuria, cal scenario.
patients with hypercalciuria were found to have higher uri-
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nary sodium and sodium intake. In a randomized trial com- Index patient 1: Calcium oxalate or mixed calcium oxalate/calcium
paring low-calcium diet to low-sodium and animal protein, phosphate stone
the low-sodium and animal protein diet resulted in fewer
stone recurrences. High sodium intake was associated Patients with calcium oxalate or combined calcium oxalate-
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with up to 61% increase in stone risk in a large prospective calcium phosphate stones may have normal 24-hour urine
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cohort of women. In a randomized trial of 210 patients testing, hypercalciuria, hyperoxaluria, hypocitraturia, hyper-
with hypercalciuria and calcium stones, a low-sodium diet uricosuria, low urine volume, or a combination of any of
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resulted in lower urinary sodium, as well as lower urinary these features. All patients should be counselled regard-

CUAJ • November-December 2016 • Volume 10, Issues 11-12 E351