Association between dietary pattern and metabolic disorders in children and adolescents with urolithiasis

A New Perspective on Gas Chromatography-Mass Spectrometry Urinary Metabolomic Analysis and Efficient Risk Assessment of Urolithiasis: Morning Urine Organic Acid Profiles

INTRODUCTION

Urolithiasis is characterized by a high morbidity and recurrence rate, primarily attributed to metabolic disorders. The identification of more metabolic biomarkers would provide valuable insights into the etiology of stone formation and the assessment of disease risk. The present study aimed to seek potential organic acid (OA) biomarkers from morning urine samples and explore new methods based on machine learning (ML) for metabolic risk prediction of urolithiasis.

METHODS

Morning urine samples were collected from 117 healthy controls and 156 urolithiasis patients. Gas chromatography-mass spectrometry was used to obtain metabolic profiles. Principal component analysis and ML were carried out to screen robust markers and establish a prediction evaluation model.

RESULTS

There were 25 differential metabolites identified, such as palmitic acid, l-pyroglutamic acid, glyoxylate, and ketoglutarate, mainly involving arginine and proline metabolism, fatty acid degradation, glycine, serine, and threonine metabolism, glyoxylate and dicarboxylic acid metabolism. The urinary OA markers significantly improved the performance of the ML model. The sensitivity and specificity were up to 87.50% and 84.38%, respectively. The area under the receiver operating characteristic curve (AUC) was significantly improved (AUC = 0.9248).

CONCLUSION

The results suggest that OA profiles in morning urine can improve the accuracy of predicting urolithiasis risk and possibly help understand the involvement of metabolic perturbations in metabolic pathways of stone formation and to provide new insights.

Impact of low-oxalate diet on hyperoxaluria among patients suffering from nephrolithiasis

Low-oxalate diets are useful for treating hyperoxaluria in nephrolithiasis patients. This study was unique in examining how a low-oxalate diet in addition to a standard diet affected hyperoxaluria and renal function tests in nephrolithiasis patients. The effects of a low-oxalate diet were analyzed by different biochemical tests, that is, anthropometric measurements, blood oxalate test, renal function test, electrolyte profile test, and 24 h urine analysis. For this purpose, 112 patients were divided into 2 groups: Group T1 (Conventional diet) and Group T2 (Low-Oxalate diet) for 8 weeks. Each group was tested at the initiation and end of the study. Using SPSS, the obtained data from each parameter were statistically analyzed. The results showed that a low-oxalate diet had a positive effect on patients suffering from nephrolithiasis. Furthermore, after treatment, anthropometric measurement weight (kg) among the control group (T1) was 100.45 ± 5.65 and the treatment group (T2) was 79.71 ± 9.48 kg. The effect of low-oxalate diet on renal function test: creatinine (g/d) among T1 was 2.08 ± 0.86 and T2 was 1.17 ± 0.13, uric acid(mg/d) among T1 was 437.04 ± 24.20 and T2 was 364.61 ± 35.99, urinary oxalate (mg/d) among T1 was 76.84 ± 10.33 and T2 was 39.24 ± 1.51, respectively. Sodium (mEq/d) among T1 was 156.72 ± 6.37 and T2 was 159.84 ± 6.31, potassium (mEq/d) among T1 was 69.91 ± 15.37 and T2 was 89.21 ± 6.31, phosphorus (g/d) among T1 was 0.96 ± 0.07 and T2 was 0.34 ± 0.27, respectively. This study demonstrated that nephrolithiasis patients with hyperoxaluria benefit from low-oxalate diets. Hyperoxaluria patients should eat a low-oxalate diet to use oxalate without affecting metabolism and eliminate it from the kidney without stones.

Popular Diets and Kidney Stones

Popular diets often influence dietary patterns, which have different implications for kidney stone risk. Despite the wide variety of popular diets, some general principles can be gleaned from investigating their potential impact on nephrolithiasis. Plant-based diets, including Dietary Approaches to Stop Hypertension, Mediterranean, flexitarian, and vegetarian diets, may protect against nephrolithiasis when they consist largely of unprocessed plant foods, while carbohydrate-restricted diets (including high-protein diets and the ketogenic diet) may raise kidney stone risk. Patients should be advised to consume a diet rich in whole plants, particularly fruits and vegetables, and minimize their consumption of animal proteins. Accompanying fruits and vegetables that are higher in oxalate content with more water and some dairy intake may also be useful. (We address the oxalate content of fruits and vegetables further below). Calcium consumption is an important component of decreasing the risk of kidney stones, as higher dietary calcium from dairy or nondairy sources is independently associated with lower kidney stone risk. Patients should also be advised to be conscious of fat intake, as fat in the intestinal lumen may complex with calcium and therefore increase urinary oxalate excretion. Finally, patients should avoid consumption of processed foods, which often contain added fructose and high sodium content, two factors that increase kidney stone risk.

Metabolic evaluation: is there really a future?

PURPOSE OF REVIEW

To confirm the need for a metabolic evaluation in stone formers based on the latest information published in the last 24 months and in the current 2022 American and European urological guidelines.

RECENT FINDINGS

Recent studies suggest that urolithiasis prevalence has been increasing since 1990. Along with it, metabolic abnormalities that contribute to the development of kidney stones are also increasing, such as hyperuricosuria, hyperoxaluria, hypocitraturia, hypomagnesuria, hypocalciuria, hypophosphaturia, and hyperuricemia. Those abnormalities can only be detected through a metabolic evaluation in patients with stone disease.

SUMMARY

It is important for us, urologists, to have in mind the actual stone prevalence worldwide. As part of our initial evaluation of the patient with urolithiasis, we must not forget to perform the basic metabolic analysis and, according to the patient's risk classification, continue with a deep metabolic analysis. This extensive analysis includes blood and urine tests. The urinalysis covers 24-h urinalysis, and it would be accurate to also have an early fresh urine analysis. Moreover, identifying the stone type is intimately correlated with the search for other metabolic parameters.

Monogenic urinary lithiasis in Tunisian children: 25 years' experience of a referral center

OBJECTIVE

To describe the clinical, biochemical and evolutive profile of monogenic urinary lithiasis in Tunisian children followed up in a reference service, during a 25 years period.

METHODS

This was a single-center retrospective observational study of children with urolithiasis, conducted in the pediatric nephrology department in Charles Nicolle Hospital, Tunis, Tunisia over 25 years (January 1st, 1996 to December 31, 2020). Children≤18 of age with urolithiasis with or without nephrocalcinosis related to a monogenic disease were included in our study.

RESULTS

A total of 66 children were included in our study. Patients were 5.92±3.48 years of age at the time of urolithiasis diagnosis, and 5.33±3.66 years of age at the time of the underlying pathology diagnosis. The inherited urolithiasis disorders found in our series were: primary hyperoxaluria in 44 cases, cystinuria in 9 cases, Lesch Nyhan syndrome in 5 cases. Renal tubular acidosis was found in 3 cases, and hereditary xanthinuria in 2 cases. Bartter syndrome, adenine phosphoribosyltransferase deficiency and Hereditary hypophosphatemic rickets with hypercalciuria were found in 1 case each. After an average follow-up of 6.45±3.79 years, six patients were in end-stage renal disease. Three patients had died, all of them being followed for primary hyperoxaluria type 1.

CONCLUSIONS

Monogenic urinary lithiasis, although rare, are most likely under-diagnosed in countries with high consanguinity such as Tunisia. The screening of these diseases seems to be of primary importance because of their significant morbidity.

Optimal Delivery of Follow-Up Care for the Prevention of Stone Recurrence in Urolithiasis Patients: Improving Outcomes

Urolithiasis is a common clinical condition with frequent recurrences. Advances in knowledge of pathophysiological mechanisms permit the categorization of patients to low and high risk for recurrence, with specific metabolic abnormalities diagnosed in the second category. Follow-up is essential for patients with urolithiasis and consists of both imaging and metabolic follow-up with urine studies. No formal guidelines or solid evidence currently exists regarding frequency and type of follow-up studies to be performed in each category. This review aims to summarize existing evidence regarding follow-up, in order to guide clinicians on how and when to follow-up urolithiasis patients according to existing clinical scenario.

Effect of age, BMI, and gender on urinary risk factors in pediatric idiopathic stone formers

INTRODUCTION

The incidence of pediatric urolithiasis has been increasing over the years; however, the etiology of this increase is not well understood. Age, body mass index, and gender have been examined as possible risk factors for stone disease, but with inconsistent and variable associations.

OBJECTIVE

We aim to investigate the urine chemistry factors, as assessed by 24-h urinary parameters, in pediatric stone formers at a large volume tertiary referral center in the highest areas in the United States, the Southeast, based on age, body mass index, and gender.

STUDY DESIGN

We retrospectively reviewed all pediatric stone formers who completed a 24-h study between 2005 and 2016. Patients were stratified by age (3-10 versus 11-18 years of age), overweight status (above versus below the 85th percentile for body mass index), and gender (male versus female) (Summary Figure). Statistical analysis included analysis of variance and logistic regression.

RESULTS

243 patients were included in our analysis. Patients in the first decade of life were found to have greater numbers of urinary risk factors than those in the second decade. Non-overweight patients were more likely to have hyperoxaluria and hyperuricosuria, while overweight patients were more likely to have hypocitraturia. Female patients were more likely to have higher hyperoxaluria, while male patients were more likely to have hypercalciuria.

DISCUSSION

In contrast to prior publications, obesity is not linked to increased risk of urolithiasis with non-overweight individuals having a greater number of risk factors than the overweight cohort. Despite stone disease being more prevalent in adolescents, the greatest number of risk factors were present in the first decade of life. Lastly, female children had more urinary risk factors than males. Further understanding of the underlying causes of stone disease in various pediatric populations is warranted.

CONCLUSION

While more urinary risk factors were identified in younger, non-overweight, and female patients, there remains no consensus on the urinary risk factors for pediatric urolithiasis. Further study is needed to elucidate the risk factors and pathophysiology of pediatric stone disease.

A study of crystalluria: effectiveness of including hygienic-dietary recommendations in laboratory reports

Objectives

To assess the effectiveness of incorporating hygienic-dietary recommendations in laboratory reports in reducing the incidence of renal colic (RC). A study was performed to compare the incidence of RC in two groups of patients who had suffered at least a crystalluria event associated with the risk of urolithiasis. Recommendations were only incorporated in the laboratory reports of one group.

Methods

A retrospective observational study. The study sample was composed of patients who had at least an episode of crystalluria associated with a higher risk of urolithiasis. The laboratory reports of patients in Group A (n=1,115), treated in 2017, did not include any hygienic-dietary recommendations, whereas patients in Group B (n=1,692), treated in 2018, received hygienic-dietary recommendations through their laboratory reports. χ² and Mann-Whitney U test were used to assess differences based on sex, age, and type of urinary crystals.

Results

The incidence of RC was 2.02 times higher in group A (2.24%) than in group B (1.12%). No significant differences were observed in the incidence of RC based on the type of urinary crystal. The incidence of RC was substantially higher in patients who suffered at least an event of crystalluria associated with a higher risk for urolithiasis as compared to the general population during the same period (0.46%, consistently with the incidence rates reported in the literature).

Conclusions

The incorporation of messages alerting on the risk of urolithiasis and the inclusion of hygienic-dietary recommendations in laboratory reports may be useful for reducing the incidence of RC.