Effect of dietary treatment and fluid intake on the prevention of recurrent calcium stones and changes in urine composition: A meta-analysis and systematic review

To perform a systematic review and meta-analysis of randomized controlled trials (RCTs) for investigating the effect of dietary treatment and fluid intake on the prevention of recurrent calcium stones and changes in urine composition. PubMed, Web of Science, Embase, EBSCO, and Cochrane Library databases (updated November 2020) were searched for studies with the following keywords: diet, fluid, recurrent, prevention, randomized controlled trials, and nephrolithiasis. The search strategy and study selection process was conducted by following the PRISMA statement. Six RCTs were identified for satisfying the inclusion criteria and enrolled in this meta-analysis. Our result showed that low protein with or without high fiber diet intervention does not decrease the recurrence of stone upon comparing with control groups (RR = 2.32, 95% CI = 0.42–12.85; P = 0.34) with significant heterogeneity among the studies (I² = 81%, P = 0.02). But normal-calcium, low protein, low-salt diet had recurrences did reduced the recurrence compared to normal-calcium diet. And the fluid intake has a positive effect on prevention of recurrent stone formation (RR = 0.39, 95% CI = 0.19–0.80; P = 0.01) with insignificant heterogeneity among the studies (I² = 9%, P = 0.30). The different components of urine at baseline were reported in four studies. Upon reviewing the low protein with or without high fiber dietary therapy groups, it was found that there were no obvious changes in the 24-hour urine sodium, calcium, citrate, urea, and sulfate. In conclusion, our study shows that the only low protein with or without fiber does not affect recurrence, but low Na, normal Ca diet has a marked effect on reducing recurrence of calcium stone. And fluid intake shows a significant reduction in the recurrence of calcium stone.

The Impact of Dietary Modifications and Medical Management on 24-Hour Urinary Metabolic Profiles and the Status of Renal Stone Disease in Recurrent Stone Formers

BACKGROUND

Dietary modifications and patient-tailored medical management are significant in controlling renal stone disease. Nevertheless, the literature regarding effectiveness is sparse.

OBJECTIVES

To explore the impact of dietary modifications and medical management on 24-hour urinary metabolic profiles (UMP) and renal stone status in recurrent kidney stone formers.

METHODS

We reviewed our prospective registry database of patients treated for nephrolithiasis. Data included age, sex, 24-hour UMP, and stone burden before treatment. Under individual treatment, patients were followed at 6-8 month intervals with repeat 24-hour UMP and radiographic images. Nephrolithiasis-related events (e.g., surgery, renal colic) were also recorded. We included patients with established long-term follow-up prior to the initiation of designated treatment, comparing individual nephrolithiasis status before and after treatment initiation.

RESULTS

Inclusion criteria were met by 44 patients. Median age at treatment start was 60.5 (50.2-70.2) years. Male:Female ratio was 3.9:1. Median follow-up was 10 (6-25) years and 5 (3-6) years before and after initiation of medical and dietary treatment, respectively. Metabolic abnormalities detected included: hypocitraturia (95.5%), low urine volume (56.8%), hypercalciuria (45.5%), hyperoxaluria (40.9%), and hyperuricosuria (13.6%). Repeat 24-hour UMP under appropriate diet and medical treatment revealed a progressive increase in citrate levels compared to baseline and significantly decreased calcium levels (P = 0.001 and 0.03, respectively). A significant decrease was observed in stone burden (P = 0.001) and overall nephrolithiasis-related events.

CONCLUSIONS

Dietary modifications and medical management significantly aid in correcting urinary metabolic abnormalities. Consequently, reduced nehprolithiasis-related events and better stone burden control is expected.

Dietary vinegar prevents kidney stone recurrence via epigenetic regulations

BACKGROUND

Epidemiological evidence of over 9000 people suggests that daily intake of vinegar whose principal bioactive component is acetic acid is associated with a reduced risk of nephrolithiasis. The underlying mechanism, however, remains largely unknown.

METHODS

We examined the in vitro and in vivo anti-nephrolithiasis effects of vinegar and acetate. A randomized study was performed to confirm the effects of vinegar in humans.

FINDINGS

We found individuals with daily consumption of vinegar compared to those without have a higher citrate and a lower calcium excretion in urine, two critical molecules for calcium oxalate (CaOx) kidney stone in humans. We observed that oral administration of vinegar or 5% acetate increased citrate and reduced calcium in urinary excretion, and finally suppressed renal CaOx crystal formation in a rat model. Mechanism dissection suggested that acetate enhanced acetylation of Histone H3 in renal tubular cells and promoted expression of microRNAs-130a-3p, -148b-3p and -374b-5p by increasing H3K9, H3K27 acetylation at their promoter regions. These miRNAs can suppress the expression of Nadc1 and Cldn14, thus enhancing urinary citrate excretion and reducing urinary calcium excretion. Significantly these mechanistic findings were confirmed in human kidney tissues, suggesting similar mechanistic relationships exist in humans. Results from a pilot clinical study indicated that daily intake of vinegar reduced stone recurrence, increased citrate and reduced calcium in urinary excretion in CaOx stone formers without adverse side effects.

INTERPRETATION

Vinegar prevents renal CaOx crystal formation through influencing urinary citrate and calcium excretion via epigenetic regulations. Vinegar consumption is a promising strategy to prevent CaOx nephrolithiasis occurrence and recurrence. FUND: National Natural Science Foundations of China and National Natural Science Foundation of Guangdong Province.

[Nutritional management of kidney diseases in children]

The prevalence of various kidney diseases in children remains high in recent decades. Adequate nutrition management can enhance the effectiveness of drug treatment, slow the frequency of relapses andprevent the progression of the disease. The article is devoted to modern approaches to diet therapy in various kidney diseases in children with the defeat of tubular and glomerular appa ratus. For the first time the therapeutic diets for children with various kidney diseases are presented. Particular attention is paid to diet therapy in nephrotic syndrome (steroid-responsive and steroid-refractory). Dietary approaches with modern formulas for enteral nutrition in cases of steroid therapy complications in children with renal insufficiency (in predialysis stage and on dialysis) are described. Differentiated nutritional approaches for patients with different types of crystalluria are separately presented.

Dietary interventions for preventing complications in idiopathic hypercalciuria

BACKGROUND

Idiopathic hypercalciuria is an inherited metabolic abnormality that is characterised by excessive amounts of calcium excreted in the urine by people whose calcium serum levels are normal. Morbidity associated with idiopathic hypercalciuria is chiefly related to kidney stone disease and bone demineralisation leading to osteopenia and osteoporosis. Idiopathic hypercalciuria contributes to kidney stone disease at all life stages; people with the condition are prone to developing oxalate and calcium phosphate kidney stones. In some cases, crystallised calcium can be deposited in the renal interstitium, causing increased calcium levels in the kidneys. In children, idiopathic hypercalciuria can cause a range of comorbidities including recurrent macroscopic or microscopic haematuria, frequency dysuria syndrome, urinary tract infections and abdominal and lumbar pain. Various dietary interventions have been described that aim to decrease urinary calcium levels or urinary crystallisation.

OBJECTIVES

Our objectives were to assess the efficacy, effectiveness and safety of dietary interventions for preventing complications in idiopathic hypercalciuria (urolithiasis and osteopenia) in adults and children, and to assess the benefits of dietary interventions in decreasing urological symptomatology in children with idiopathic hypercalciuria.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (23 April 2013) through contact with the Trials' Search Co-ordinator using search terms relevant to this review. Studies contained in the Specialised Register are identified through search strategies specifically designed for CENTRAL, MEDLINE and EMBASE.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs that investigated dietary interventions aimed at preventing complications of idiopathic hypercalciuria, compared with placebo, no intervention, or other dietary interventions regardless of route of administration, dose or amount.

DATA COLLECTION AND ANALYSIS

Studies were assessed for inclusion and data extracted using a standardised data extraction form. We calculated risk ratios (RR) for dichotomous outcomes and mean differences (MD) for continuous outcomes, both with 95% confidence intervals (CI).

MAIN RESULTS

We included five studies (379 adult participants) that investigated a range of interventions. Lack of similarity among interventions investigated meant that data could not be pooled. Overall, study methodology was not adequately reported in any of the included studies. There was a high risk of bias associated with blinding (although it seems unlikely that outcomes measures were unduly influenced by lack of intervention blinding), random sequence generation and allocation methodologies were unclear in most studies, but selective reporting bias was assessed as low.One study (120 participants) compared a low calcium diet with a normal calcium, low protein, low salt diet for five years. There was a significant decrease in numbers of new stone recurrences in those treated with the normal calcium, low protein, low salt diet (RR 0.77, 95% CI 0.61 to 0.98). This diet also led to a significant decrease in oxaluria (MD 78.00 µmol/d, 95% CI 26.48 to 129.52) and the calcium oxalate relative supersaturation index (MD 1.20 95% CI 0.21 to 2.19).One study (210 participants) compared a low salt, normal calcium diet with a broad diet for three months. The low salt, normal calcium diet decreased urinary calcium (MD -45.00 mg/d, 95% CI -74.83 to -15.17) and oxalate excretion (MD -4.00 mg/d, 95% CI -6.44 to -1.56).A small study (17 participants) compared the effect of dietary fibre as part of a low calcium, low oxalate diet over three weeks, and found that although calciuria levels decreased, oxaluria increased. Phyllanthus niruri plant substrate intake was investigated in a small subgroup with hypercalciuria (20 participants); there was no significant effect on calciuria levels occurred after three months of treatment.A small cross-over study (12 participants) evaluating the changes in urinary supersaturation indices among patients who consumed calcium-fortified orange juice or milk for one month found no benefits for participants.None of the studies reported any significant adverse effects associated with the interventions.

AUTHORS' CONCLUSIONS

Long-term adherence (five years) to diets that feature normal levels of calcium, low protein and low salt may reduce numbers of stone recurrences, decrease oxaluria and calcium oxalate relative supersaturation indexes in people with idiopathic hypercalciuria who experience recurrent kidney stones. Adherence to a low salt, normal calcium level diet for some months can reduce calciuria and oxaluria. However, the other dietary interventions examined did not demonstrate evidence of significant beneficial effects.No studies were found investigating the effect of dietary recommendations on other clinical complications or asymptomatic idiopathic hypercalciuria.

[Diet in the treatment of renal lithiasis. Pathophysiological basis]

The composition of urine is influenced by diet and changes in dietary factors have been proposed to modify the risk of recurrent nephrolithiasis. Nutrients that have been implicated include calcium, oxalate, sodium, animal protein, magnesium and potassium. There is significant evidence showing that a high calcium diet is associated with a reduction of lithogenic risk. One of the possible mechanisms to explain this apparent paradox is that the higher intake of calcium in the intestine binds with dietary oxalate, reducing its absorption and urinary excretion. Oxalate from the diet seems to provide only a small contribution to excretion and dietary restriction is appropriate only in those with hyperoxaluria and hyperabsorption. Observational studies have shown a positive and independent association between sodium intake and the formation of new kidney stones. Consumption of animal protein creates an acid load that increases urinary excretion of calcium and uric acid and reduced citrate, all factors that could participate in the genesis of stones. Potassium-rich foods increase urinary citrate because of its alkali content. In prospective observational studies, diets rich in magnesium were associated with a lower risk of kidney stone formation in men. In conclusion, diet is a key element in the management of the patient with kidney stones but always subordinated to present metabolic risk factors.

Citrate, malate and alkali content in commonly consumed diet sodas: implications for nephrolithiasis treatment

PURPOSE

Citrate is a known inhibitor of calcium stone formation. Dietary citrate and alkali intake may have an effect on citraturia. Increasing alkali intake also increases urine pH, which can help prevent uric acid stones. We determined citrate, malate and total alkali concentrations in commonly consumed diet sodas to help direct dietary recommendations in patients with hypocitraturic calcium or uric acid nephrolithiasis.

MATERIALS AND METHODS

Citrate and malate were measured in a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis and in 15 diet sodas. Anions were measured by ion chromatography. The pH of each beverage was measured to allow calculation of the unprotonated anion concentration using the known pK of citric and malic acid. Total alkali equivalents were calculated for each beverage. Statistical analysis was done using Pearson's correlation coefficient.

RESULTS

Several sodas contained an amount of citrate equal to or greater than that of alkali and total alkali as a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis (6.30 mEq/l citrate as alkali and 6.30 as total alkali). These sodas were Diet Sunkist Orange, Diet 7Up, Sprite Zero, Diet Canada Dry Ginger Ale, Sierra Mist Free, Diet Orange Crush, Fresca and Diet Mountain Dew. Colas, including Caffeine Free Diet Coke, Coke Zero, Caffeine Free Diet Pepsi and Diet Coke with Lime, had the lowest total alkali (less than 1.0 mEq/l). There was no significant correlation between beverage pH and total alkali content.

CONCLUSIONS

Several commonly consumed diet sodas contain moderate amounts of citrate as alkali and total alkali. This information is helpful for dietary recommendations in patients with calcium nephrolithiasis, specifically those with hypocitraturia. It may also be useful in patients with low urine pH and uric acid stones. Beverage malate content is also important since malate ingestion increases the total alkali delivered, which in turn augments citraturia and increases urine pH.

Diet, fluid, or supplements for secondary prevention of nephrolithiasis: a systematic review and meta-analysis of randomized trials

CONTEXT

Although numerous trials have evaluated efficacy of diet, fluid, or supplement interventions for secondary prevention of nephrolithiasis, few are included in previous systematic reviews or referenced in recent nephrolithiasis management guidelines.

OBJECTIVE

To determine efficacy and safety of diet, fluid, or supplement interventions for secondary prevention of nephrolithiasis.

EVIDENCE ACQUISITION

Systematic review and meta-analysis of trials published January 1950 to March 2008. Sources included Medline and bibliographies of retrieved articles. Eligible trials included adults with a history of nephrolithiasis; compared diet, fluids, or supplements with control; compared relevant outcomes between randomized groups (eg, stone recurrence); had > or = 3 mo follow-up; and were published in the English language. Data were extracted on participant and trial characteristics, including study methodologic quality.

EVIDENCE SYNTHESIS

Eight trials were eligible (n=1855 participants). Study quality was mixed. In two trials, water intake > 2 l/d or fluids to achieve urine output > 2.5 l/d reduced stone recurrence (relative risk: 0.39; 95% confidence interval: 0.19-0.80). In one trial, fewer high soft drink consumers assigned to reduced soft drink intake had renal colic than controls (34% vs 41%, p=0.023). Content and results of multicomponent dietary interventions were heterogeneous; in one trial, fewer participants assigned increased dietary calcium, low animal protein, and low sodium had stone recurrence versus controls (20% vs 38%, p=0.03), while in another trial, more participants assigned diets that included low animal protein, high fruit and fiber, and low purine had recurrent stones than controls (30% vs 4%, p=0.004). No trials examined the independent effect of altering dietary calcium, sodium, animal protein, fruit and fiber, purine, oxalate, or potassium. Two trials showed no benefit of supplements over control treatment. Adverse event reporting was poor.

CONCLUSIONS

High fluid intake decreased risk of recurrent nephrolithiasis. Reduced soft drink intake lowered risk in patients with high baseline soft drink consumption. Data for other dietary interventions were inconclusive, although limited data suggest possible benefit from dietary calcium.

A case-control study of the effects of nephrolithiasis in cats with chronic kidney disease

OBJECTIVE

To determine whether nephrolithiasis was associated with an increase in mortality rate or in the rate of disease progression in cats with naturally occurring stage 2 (mild) or 3 (moderate) chronic kidney disease.

DESIGN

Retrospective case-control study.

ANIMALS

14 cats with stage 2 (mild) or 3 (moderate) chronic kidney disease (7 with nephroliths and 7 without).

PROCEDURES

All cats were evaluated every 3 months for up to 24 months. Possible associations between nephrolithiasis and clinicopathologic abnormalities, incidence of uremic crises, death secondary to renal causes, and death secondary to any cause were evaluated.

RESULTS

There were no clinically important differences in biochemical, hematologic, or urinalysis variables between cats with and without nephroliths at baseline or after 12 and 24 months of monitoring. No associations were detected between nephrolithiasis and rate of disease progression, incidence of uremic crises, or death.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in cats with mild or moderate chronic kidney disease, nephrolithiasis was not associated with an increase in mortality rate or in the rate of disease progression. Findings support recommendations that cats with severe kidney disease and nephrolithiasis be managed without surgery.

Long-term lemonade based dietary manipulation in patients with hypocitraturic nephrolithiasis

PURPOSE

Citrus fruits and juices are a known natural source of dietary citrate. Of all the citrus juices, lemon juice appears to have the highest concentration of citrate. Therefore, lemonade therapy has been proposed as a potential treatment for patients with hypocitraturia. We retrospectively evaluated the impact of long-term lemonade therapy on urinary metabolic parameters and stone formation in patients with hypocitraturic nephrolithiasis.

MATERIALS AND METHODS

A total of 32 patients were identified as being on long-term lemonade therapy for hypocitraturic nephrolithiasis. The 11 patients on lemonade therapy who met the entrance criteria for evaluation were compared to an age and sex matched control group of patients treated with oral slow release potassium citrate. Pre-therapy and post-therapy urinary parameters were recorded for both groups. The effect of lemonade therapy on stone burden and stone formation rate was calculated. New stone formation was defined as passage, surgical removal or appearance of new stones, or an increase in the size of existing stones on radiographic imaging.

RESULTS

Four males and 7 females (mean age 52.7 years) were treated with lemonade therapy for a mean of 44.4 months. The control group consisted of 4 males and 7 females (mean age 54.5 years) treated with potassium citrate for a mean of 42.5 months. Of the 11 patients on lemonade 10 demonstrated increased urinary citrate levels (mean increase +383 mg per day, p <0.05). All potassium citrate therapy subjects demonstrated an increase in urinary citrate (mean increase +482 mg per day, p <0.0001). Mean pretreatment and posttreatment stone burden in the lemonade group was 37.2 and 30.4 mm(2), respectively (p >0.05). During lemonade therapy the stone formation rate decreased from 1.00 to 0.13 stones per patient per year (p >0.05).

CONCLUSIONS

Due to its significant citraturic effect, lemonade therapy appears to be a reasonable alternative for patients with hypocitraturia who cannot tolerate first line therapy. Future study in the form of a prospective, randomized trial is needed to validate these findings.

[Diet and nutrition in nephrolitiasis]

Nephrolitiasis is a frequent metabolic disease, with a high rate of recurrences. Epidemiological studies reveal that about 80% of all kidney stones are composed of calcium salts (75% calcium oxalate), while about 5% are pure uric acid. Urolithiasis is a multifactorial disease with several underlying disorders of metabolism: that is why diet is an important treatment, especially in the prevention of recurrences. Nutritional intervention is based on a high water intake, physiological calcium intake, modest sodium and animal protein restriction and vitamin C intake <2 gr daily. In case of diagnosed disorders of specific metabolic pathways, a low oxalate, low purine-diet should be advisable.