Recent advances in nutritional research on urolithiasis

Fluid intake recommendations in urolithiasis and general advice to patients without metabolic risk factors

Urolithiasis is a highly prevalent global disease with substantially increasing incidence in the last two decades. Data from the literature suggests that 26%-50% of patients will have a recurrence within 10 years after an initial symptomatic stone episode. Therefore, interest has been raised in preventive strategies, aiming to modify the risk factors of stone recurrence by implementing dietary and lifestyle changes and specific medical treatments for stone formers, depending on their recurrence risk factors. Certain dietary factors are thought to contribute significantly to the increased incidence of urolithiasis, particularly a diet low in fiber and high in animal protein, fat, and sodium. Fluid intake is perhaps the most important and modifiable step in the prevention of urolithiasis, irrespective of stone composition. However, the amount of fluid to be consumed and the implications of various fluid types on stone formation are still controversial. In this article, the relationship between fluid intake, beverage types and stone formation-prevention will be discussed. Moreover, general dietary recommendations for patients without metabolic risk factors will be reviewed based on the current literature.

Effects of high-sodium diet on lithogenesis in a rat experimental model of calcium oxalate stones

Background

This study aimed to investigate the effects of a high- and low-sodium diets on lithogenesis in a rat experimental model of calcium oxalate stones.

Methods

Twenty male Wistar rats were randomly divided into four groups; group A: 4% NaCl+1% ethylene glycol (EG); group B: 8% NaCl+1% EG; group C: 8% NaCl+normal drinking-water; group D: 1% EG +normal diet. All rats were sacrificed 4 weeks later, and blood samples were collected from the heart. The kidneys were collected for Von Kossa staining to evaluate the formation of calcium-containing crystals. The last 24-h urine samples were also gathered for metabolic analysis.

Results

Von Kossa staining demonstrated that the rats in both group A and group B had significantly more renal calcium crystals than those in group D. However, 24-h urinary volume increased significantly (142.26±20.91 mL) in group B compared with group A (100.52±28.23 mL), group C (107.36±14.24 mL), group D (40.79±8.71 mL) (P=0.004, 0.012, and 0.000 respectively). Level of urine sodium (Na), potassium (K), chlorine (Cl), and calcium (Ca), urea nitrogen were significantly higher in group B compared with group D. The urine phosphorus, oxalate, and creatinine levels; urine specific gravity; and urine PH were similar between group B and group D. The level of serum sodium was higher in group B (151.26±4.06 mmol/L) compared with group D (145.56±1.12 mmol/L) (P=0.002).

Conclusions

A high sodium intake might increase the risk of lithogenesis in susceptible individuals (given by EG) or in individuals with water restriction.

Spectrum of chronic kidney disease in China: A national study based on hospitalized patients from 2010 to 2015

AIM

To investigate the spectrum of chronic kidney disease (CKD) in China.

METHODS

We used a large national in-patient database covering 878 class three hospitals and involving 64.7 million adult patients in China from 2010 to 2015. The class 3 hospital in China is ranked as the top tier of medical system in China with at least 500 beds and the accreditation from health authorities. The specific causes of CKD were extracted from the International Classification of Diseases-10 codes of discharge diagnoses.

RESULTS

A total of 4.5% of hospitalized patients (1.8 million) were identified as CKD, with an increased percentage from 2010 (3.7%) to 2015 (4.7%). Increasing trends of diabetic kidney disease and hypertensive nephropathy were observed from 2010 to 2015 (19.5% vs 24.3% and 11.5% vs 15.9%, respectively), especially for urban residents from north China. The proportion of obstructive nephropathy also increased gradually (10.3% in 2010 vs 15.6% in 2015) and constituted another important cause of CKD for patients, especially for those from south China and rural residents.

CONCLUSION

The spectrum of CKD is changing in China, with variations over time and geographic regions, which has implication regarding developing the prevention strategy of CKD.

The association between dietary intakes and stone formation in patients with urinary stones in Shiraz

Background: Kidney stone is a common and costly disease, but it may be improved by a healthy diet. The aim of this study was to evaluate the association between dietary intake and stone formation in patients with urinary stones in Shiraz. Methods: In this cross sectional study, 110 patients with kidney stone were selected from Faghihi hospital, Shiraz. Demographic information was collected, and anthropometric indices, disease-related variables, physical activity (using IPAQ), and dietary intake (using food frequency questionnaire, analyzed by Nut 4 software, to estimate micro and macro nutrients) were evaluated. Independent sample t test and one-way ANOVA were used to compare the quantitative variables between the 2 groups and multi groups, respectively. Chi square test was also used to compare qualitative variables. The correlation between variables was determined using Pearson test. Results: Out of 110 participants in this study, 37 (33.6%) were female, with the mean BMI of 27.0 ± 4.68 kg/m2, and 73 (66.4%) were male, with the mean BMI of 24.21±2.96 kg/m2. The mean intake of calcium-containing foods (p=0.02) and high-fructose beverages (p=0.03) was significantly greater in patients with calcium stones compared to those with uric acid stones. The mean intake of high-purine foods was significantly higher in patients with uric acid stones than in those with calcium stones (p=0.007). The mean intake of vitamin A (p=0.02), beta-carotene (p=0.03), and fructose (p=0.03) was significantly higher in patients with calcium stones than in those with uric acid stones, while caffeine intake was significantly higher in patients with uric acid than in those with calcium stones (p=0.01). There was a significant correlation between consumption of high-oxalic beverages (p=0.005, correlation coefficient = 0.26) and high-fructose (p=0.048, correlation coefficient = 0.18) with spontaneous stone expulsion. Conclusion: There was a significant relationship between consuming vitamin A, beta-carotene, and foods containing calcium, purine, fructose, and oxalate and formation of kidney stones. Therefore, adopting a healthy diet and increasing physical activity may be effective in the treatment of kidney stones.

Dietary factors and risk of kidney stone: a case-control study in southern China

OBJECTIVE

Formation of kidney stones is a multifactorial disease, and diet and lifestyle are suggested to contribute remarkably to increased prevalence. The population of Guangzhou, China has a high prevalence rate of kidney stones; however, its risk factors are still unknown. The aim of this study was to investigate the dietary risk factors for kidney stones in southern China.

DESIGN

A case-control study was carried out.

SETTING

This study was carried out at the Department of Health Management Center, Guangzhou Nanfang Hospital, China.

SUBJECTS

This study involved 1,019 newly diagnosed kidney stone patients and 987 healthy control subjects.

INTERVENTION

A questionnaire regarding dietary patterns and supplements was used to investigate the risk factors for kidney stone formation.

MAIN OUTCOME MEASURE

Food intake frequency, beverage and alcohol consumption, food supplements, and anthropometry were assessed.

RESULTS

In the analysis, we found positive associations of kidney stones with consumption of grains (odds ratio [OR] = 2.08; 95% confidence interval [CI] = 1.08, 4.02) and bean products (OR = 3.50; 95% CI = 1.61, 7.59) in women. The variable "fluid drinking" showed a significant protective effect against kidney stones in men (OR = 0.57; 95% CI = 0.36, 0.88). Consuming leafy vegetables more than 3 times per day was positively associated with stones in both men and women (OR = 2.02; 95% CI = 1.04, 3.91 and OR = 3.86; 95% CI = 1.48, 10.04, respectively). Other dietary factors, dietary supplements, and specific food were not related to kidney stone formation in Guangzhou, China.

CONCLUSION

The results confirmed that specific diet can affect stone formation in the Chinese population, and varied risk factors were found for different genders.

Influential nutrient in urolithiasis incidence: protein or meat?

OBJECTIVE

We evaluated the relationship between dietary regimen and the incidence of urolithiasis in various regions.

DESIGN

This was a population-based, cross-sectional study.

SETTING

The setting involved 787 imaging centers in 12 socioeconomic regions in Iran.

PATIENTS AND METHODS

Using a multistage, stratified sampling during 4 seasonal phases, 6127 cases of urolithiasis were detected from referrals to 787 radiology centers in 30 provinces across Iran. The dietary style of the provinces was obtained from an accredited registry, and its relationship with the incidence of urolithiasis in the same region was evaluated by meta-regression models.

RESULTS

No significant relationship was detected between urolithiasis incidence and daily intake of calcium, sodium chloride, or dairy products in univariate models. In contrast, the daily consumption of meat and protein had a significant correlation with the regional incidence of urolithiasis. Meat consumption had a direct correlation with the incidence of urolithiasis. Protein intake had a significant U-shaped correlation with the incidence of urolithiasis, indicating a high incidence in regions with a high-protein diet, as well as with a low-protein diet. The proportion of meat consumption to total protein intake was similar in both regions, and higher than in regions with a medium-protein intake and low incidence of urolithiasis.

CONCLUSION

A high proportion of meat consumption, in conjunction with either a low or high total protein intake, was correlated with a high regional incidence of urolithiasis.

Prevalence and epidemiological characteristics of urolithiasis in Japan: national trends between 1965 and 2005

OBJECTIVES

We evaluated the epidemiological details and chronological trends of upper urinary tract stones in Japan using a nationwide survey of urolithiasis.

METHODS

All patient visits to urologists that resulted in a diagnosis of first-episode upper urinary tract stones in 2005 were enumerated irrespective of admission and treatment. The study included all hospitals approved by the Japanese Board of Urology, thus covering nearly all urologists practicing in Japan. We compared the estimated annual incidence according to gender and age with the incidence determined from nationwide surveys between 1965 and 1995.

RESULTS

The estimated annual incidence of first-episode upper urinary tract stones in 2005 was 134.0 per 100,000 (192.0 in men and 79.3 in women). The estimated age-standardized annual incidence of first-episode upper urinary tract stones in 2005 was 114.3 per 100,000 (165.1 for men and 65.1 for women), which represents a steady increase from 54.2 in 1965. The annual incidence has increased in all age groups except during the first 3 decades of life and the peak age for both men and women has also increased.

CONCLUSIONS

The annual incidence of upper urinary tract stones has steadily increased in Japan and this trend will continue in the near future. This probably results from improvements in clinical-diagnostic procedures, changes in nutritional and environmental factors, and general apathy toward metabolic clarification and metaphylaxis.

In vitro effect of lemon and orange juices on calcium oxalate crystallization

AIM

In recent years significant progress has been made in identifying and quantitating physico-chemical processes involved in urinary stone formation. The ability of urine to inhibit calcium oxalate crystallization is an important mechanism against stone formation. Dietary factors appear to affect the ability of urine to inhibit calcium oxalate crystallization. These factors encouraged us to study the effects of lemon and orange juices on calcium oxalate crystallization in vitro.

MATERIAL AND METHODS

The nucleation and aggregation of calcium oxalate monohydrate crystals were studied using turbidimetric 30-min time course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at 37 degrees C, pH 5.7. The formation of crystals is induced by the addition of the oxalate and calcium solution. The effects on calcium oxalate crystal growth of trisodium citrate, lemon and orange juices were examined. The effects of lemon and orange juices were evaluated by the addition of 50 ml of juices. The optical density is measured at physiological conditions. The maximum increase of optic density with time, termed SN, reflects maximum rate of formation of new particles. After an equilibrium has been reached, a progressive decrease of optic density with time is observed. Rate of aggregation, SA, is derived from the maximum decrease in optic density.

RESULTS

Among the modifiers studied, citrate decreased both SN and SA (P<0.001). Lemon juice was also found to inhibit the rate of crystal nucleation and aggregation. But orange juice did not have any effect on the calcium oxalate crystallization (P>0.05).

CONCLUSION

These results show that effective prevention of urinary stone formation should aim at restoring the urine's ability to inhibit calcium oxalate crystallization and more emphasis should be given to dietary measures.

Lactobacillus gasseri Gasser AM63(T) degrades oxalate in a multistage continuous culture simulator of the human colonic microbiota

Colonic oxalate-degrading bacteria have been shown to play an important role in human kidney stone formation. In this study, molecular analysis of the Lactobacillus gasseri genome revealed a cluster of genes encoding putative formyl coenzyme A transferase (frc) and oxalyl coenzyme A decarboxylase (oxc) homologues, possibly involved in oxalate degradation. The ability of Lactobacillus gasseri Gasser AM63(T) to degrade oxalate was confirmed in vitro. Transcription of both genes was induced by oxalate, and reverse transcription-PCR confirmed that they were co-transcribed as an operon. A three-stage continuous culture system (CCS) inoculated with human fecal bacteria was used to model environmental conditions in the proximal and distal colons, at system retention times within the range of normal colonic transit rates (30 and 60 hours). A freeze-dried preparation of L. gasseri was introduced into the CCS under steady-state growth conditions. Short chain fatty acid analysis indicated that addition of L. gasseri to the CCS did not affect the equilibrium of the microbial ecosystem. Oxalate degradation was initiated in the first stage of the CCS, corresponding to the proximal colon, suggesting that this organism may have potential therapeutic use in managing oxalate kidney stone disease in humans.