Sodium restriction as initial conservative treatment for urinary stone disease

Risk factors for urinary stone

Urolithiasis is one of the most common urologic diseases in Korea. The annual incidence of urolithiasis in Korea has increased over time. Understanding the epidemiology and risk factors for urolithiasis is essential for patient care and prevention. The purpose of this review was to summarize the recent literature regarding the risk factors for urolithiasis. The available Korean-population-based trials were enrolled in this study. The peak incidence age was the fifth to sixth decades in Korea. There has been a persistent male predominance in the prevalence and incidence of stone disease. The gender gap has continuously narrowed over the world. Climate and seasonal variations, such as temperature and humidity, have a profound effect on the development of urolithiasis. Various dietary factors, including calcium, sodium, animal protein, and oxalate, play an important role in the development of urolithiasis. Dehydration is a wellknown risk factor for stone disease. Many metabolic diseases can affect urolithiasis, including obesity, hypertension, diabetes, gout, and metabolic syndrome. The fast-moving super-aged society and global warming can increase stone disease burden in the near future. To prevent and reduce stone diseases, clinicians should understand the risk factors affecting stone formation.

Biochemical Alterations in Patients with Oxalocalcic Lithiasis, the Influence of Sex, Age, and Body Mass Index

Background: Urolithiasis is a disorder that has a high prevalence in the population. Also, lithiasic patients have biochemical alterations that predispose them to the formation of stones. The knowledge of these alterations may be useful for future preventive interventions. Objectives: The objectives were to describe the metabolic characteristics of patients with oxalocalcic lithiasis, identifying the most frequent biochemical alterations, and their variation with different demographic variables. In this way, we can prevent the formation of the lithiasis before it appears, instead of treating it once established. Methods: A descriptive cross-sectional study of serum and 24 hour-urine parameters in patients with oxalocalcic lithiasis was performed. The most frequent biochemical alterations were described, and their association with age, sex, and body mass index (BMI) were assessed. Results: In this study, 100% of the 151 patients had biochemical alterations, the most frequent being hypocitraturia (84.7%), hypercalciuria (51.7%), and urinary pH decrease (44.4%). There were differences according to sex, age, and BMI with regard to the biochemical alterations. Hypouricemia, hypouricosuria, hypophosphaturia and hypomagnesuria were more frequent in women. Men had a higher percentage of hyperzinquemia, hyperphosphaturia, and excess of urinary urea. Urine density in men was slightly higher than in women. A higher percentage of hyperphosphaturia, excess urinary urea, and excess of serum urea was found in overweight patients. Patients not overweight showed a higher percentage of hypouricemia and hypomagnesuria. Urinary density was slightly higher in overweight patients. Urinary volume was higher in middle-aged subjects. Conclusions: Patients with oxalocalcic lithiasis have biochemical alterations that may predispose to stone formation. These alterations vary with sex, age, and BMI.

Low Sodium Diet Decreases Stone Formation in Genetic Hypercalciuric Stone-Forming Rats

BACKGROUND

Urine (u) calcium (Ca) excretion is directly dependent on dietary sodium (Na) intake leading to the recommendation for Na restriction in hypercalciuric kidney stone formers. However, there is no direct evidence that limiting Na intake will reduce recurrent stone formation.

MATERIALS AND METHODS

We used genetic hypercalciuric stone-forming (GHS) rats, which universally form Ca phosphate (P) kidney stones, fed either a low Na (LNa, 0.05%) or normal Na (NNa, 0.4%) Na diet (D) for 18 weeks. Urine was collected at 6-week intervals. Radiographic analysis for stone formation and bone analyses were done at the conclusion of the study.

RESULTS

Mean uCa was lower with LNaD than NNaD as was uP and LNaD decreased mean uNa and uChloride. There were no differences in urine supersaturation (SS) with respect to calcium phosphate (CaP) or Ca oxalate (CaOx). However, stone formation was markedly decreased with LNaD by radiographic analysis. The LNaD group had significantly lower femoral anterior-posterior diameter and volumetric bone mineral density (vBMD), but no change in vertebral trabecular vBMD. There were no differences in the bone formation rate or osteoclastic bone resorption between groups. The LNaD group had significantly lower femoral stiffness; however, the ultimate load and energy to fail was not different.

CONCLUSION

Thus, a low Na diet reduced uCa and stone formation in GHS rats, even though SS with respect to CaP and CaOx was unchanged and effects on bone were modest. These data, if confirmed in humans, support dietary Na restriction to prevent recurrent Ca nephrolithiasis.

Dietary risk factors for urolithiasis in Korea: A case-control pilot study

Purpose

Dietary factors are one of the main causes of urolithiasis. However, little research has evaluated dietary factors related to urolithiasis in Korea. We investigated the various dietary risk factors for urinary stone formation in Korean people.

Materials and Methods

We conducted a prospective case-control pilot study. A total of 27 patients newly diagnosed with urolithiasis and 20 applicants without urolithiasis were designated as the patients and the control group, respectively. A face-to-face survey was carried out using a food-frequency questionnaire. After adjustment for physical activity level and total energy intake, multivariate logistic regression models were applied to search for risk factors for urolithiasis.

Results

There were no significant differences between the two groups in gender, age, body mass index, family history, or total energy intake. The physical activity level of the control group was significantly higher than that of the patients (p=0.012). The results of the multivariate logistic regression model demonstrated that intake of carbohydrate (odds ratio [OR], 1.055; 95% confidence interval [CI], 1.012–1.099), protein (OR, 1.101; 95% CI, 1.001–1.211), and cereals (OR, 1.012; 95% CI, 1.002–1.023) could increase the risk for urolithiasis.

Conclusions

A higher intake of carbohydrate, protein, and cereal may increase the risk of urinary stone formation among Korean people.

Decreased transcriptional activity of calcium-sensing receptor gene promoter 1 is associated with calcium nephrolithiasis

BACKGROUND

CaSR gene is a candidate for calcium nephrolithiasis. Single-nucleotide polymorphisms (SNPs) encompassing its regulatory region were associated with calcium nephrolithiasis.

AIMS

We tested SNPs in the CaSR gene regulatory region associated with calcium nephrolithiasis and their effects in kidney.

SUBJECTS AND METHODS

One hundred sixty-seven idiopathic calcium stone formers and 214 healthy controls were genotyped for four CaSR gene SNPs identified by bioinformatics analysis as modifying transcription factor binding sites. Strontium excretion after an oral load was tested in 55 stone formers. Transcriptional activity induced by variant alleles at CaSR gene promoters was compared by luciferase reporter gene assay in HEK-293 and HKC-8 cells. CaSR and claudin-14 mRNA levels were measured by real-time PCR in 107 normal kidney medulla samples and compared in patients with different CaSR genotype.

RESULTS

Only rs6776158 (A>G), located in the promoter 1, was associated with nephrolithiasis. Its minor G allele was more frequent in stone formers than controls (37.8% vs 26.4%, P = .001). A reduced strontium excretion was observed in GG homozygous stone formers. Luciferase fluorescent activity was lower in cells transfected with the promoter 1 including G allele at rs6776158 than cells transfected with the A allele. CaSR mRNA levels were lower in kidney medulla samples from homozygous carriers for the G allele at rs6776158 than carriers for the A allele. Claudin-14 mRNA levels were also lower in GG homozygous subjects.

CONCLUSIONS

Minor allele at rs6776158 may predispose to calcium stones by decreasing transcriptional activity of the CaSR gene promoter 1 and CaSR expression in kidney tubules.