Role of diet in the therapy of urolithiasis

Catastrophic retinal vascular occlusion and vision loss due to crystal deposition in end-stage kidney disease treated with peritoneal dialysis

Purpose

To report two cases of catastrophic retinal vascular occlusion and crystalline retinopathy due to presumed oxalosis and hyperphosphatemia.

Observations

We describe two unrelated patients with end-stage kidney failure (ESKD) treated with peritoneal dialysis that developed rapid bilateral vision loss due to severe retinal vascular occlusion. Multi-modal retinal imaging studies demonstrated crystalline deposits. Plasma phosphorus and oxalate levels were markedly elevated compared to persons with normal kidney function. One patient harbored a heterozygous variant of unknown significance in the Alanine--Glyoxylate Aminotransferase (AGXT) gene. Intense hemodialysis and diet modification reduced phosphorus and oxalate levels.

Conclusions and importance

This report serves to raise awareness of hyperphosphatemia and oxalosis in dialysis patients to alert providers so that they can act to decrease the potential risk of vision loss.

Dietary supplements and medicinal plants in urolithiasis: diet, prevention, and cure

BACKGROUND

Urolithiasis has been a major health concern for centuries, primarily owing to the limited treatment options in the physician's armamentarium. However, various studies have underscored a lesser incidence of urolithiasis in cohorts predominantly consuming fruits and vegetables. This article aims to review various dietary plants, medicinal herbs and phytochemicals in the prevention and management of urolithiasis.

METHODS

To provide context and evidence, relevant publications were identified on Google Scholar, PubMed and Science-Direct using keywords such as urolithiasis, nephrolithiasis, urolithiasis, renal stones, phytochemicals and dietary plants.

RESULTS

Growing bodies of evidence suggest the incorporation of plant-based foods, medicinal and herbal supplements, and crude drugs containing phytochemicals into the staple diet of people. The anti-urolithiatic activity of these plant bioactives can be attributed to their antioxidant, antispasmodic, diuretic, and inhibitory effect on the crystallization, nucleation and crystal aggregation effects. These mechanisms would help alleviate the events and symptoms that aid in the development and progression of renal calculi. In addition, it will also avoid the exacerbation of secondary disorders like inflammation and injury, which can initiate a vicious circle in turn worsening the disease progression.

CONCLUSION

In conclusion, the results presented in the review demonstrate the promising role of various dietary plants, medicinal and herbal supplements, and phytochemicals in preventing and managing the precipitation of uroliths. However, more conclusive and cogent evidence from preclinical and clinical studies is required to substantiate their safety, efficacy and toxicity profiles in humans.

Dietary oxalate to calcium ratio and incident cardiovascular events: a 10-year follow-up among an Asian population

Background and aim

The potential cardiovascular impact of usual intakes of oxalate (Ox) is uninvestigated. We evaluated the effect of dietary Ox and its interaction with dietary calcium (Ca) on incident cardiovascular disease (CVD).

Methods

We included 2966 adult men and women aged 19–84 y without known CVD during baseline enrollment (2006–2008) of the Tehran Lipid and Glucose Study. Dietary intakes were assessed using a validated FFQ, and incident CVD (i.e., coronary heart disease, stroke, and CVD mortality) were documented through March 2018.

Results

A 7.1% incident of CVD occurred during a median follow-up of 10.6 y. After multivariable adjustment for traditional risk factors and key dietary nutrients, including total fat and fiber, Ox intakes ≥220 mg/d increased incident CVD (HR T3 vs. T1 = 1.47, 95% CI = 1.02–2.12). This association was potentiated (HR T3 vs. T1 = 2.42, 95% CI = 1.19–4.89) in subjects who had a lower intake of Ca (< 981 mg/d); in a low-Ca diet, an even lower amount of dietary Ox (second tertile, 148–220 mg/d) was related to increased CVD events by 92% (HR = 1.92, 95% CI = 1.00–3.70). No association was observed between dietary Ox and CVD events in the presence of medium- and high levels of Ca intakes. The critical cut-off point of Ox-to-Ca for predicting CVD events was 0.14, which was related to an increased risk of CVD by 37% (HR = 1.37, 95% CI = 1.02–1.84).

Conclusion

Higher dietary Ox intake appeared to be associated with a modestly elevated risk of incident CVD, especially in a diet with a lower amount of Ca.

Simultaneous use of oxalate-degrading bacteria and herbal extract to reduce the urinary oxalate in a rat model: A new strategy

Objective:

Urinary stones with oxalate composition can cause kidney failure. Recent findings evidenced that probiotics are effective in reducing oxalate absorption in these subjects based on their high colonic absorption levels at baseline. The purpose of this study was to evaluate the effect of the simultaneous use of oxalate-degrading bacteria, Urtica dioica and T. terrestris extract in reducing urinary oxalate.

Materials and Methods:

Anti-urolithiatic activity of Urtica dioica and T. terrestris extract and probiotic by using ethylene glycol induced rat model. In this study, 4 strains of Lactobacillus and 2 strains of Bifidobacterium and also 2 strains of L. paracasei (that showed high power in oxalate degrading in culture media) were used. Male Wistar rats were divided into four groups (n=6). The rats of group-I received normal diet (positive control group) and groups-II (negative control group), III, IV rats received diet containing ethylene glycol (3%) for 30 days. Groups III rats received Urtica dioica and T. terrestris extract. Groups IV rats received extracts + probiotic for 30 days.

Findings:

The results show that the use of herbal extracts (Urtica dioica and T. terrestris) reduced the level of urinary oxalate and other parameters of urine and serum. Also, the accumulation of calcium oxalate crystals in the kidney tissue was significantly reduced.

Conclusion:

Considering that the formation of calcium oxalate crystals can cause inflammation and tissue damage in the kidney, the use of herbal extracts with oxalate degrading bacteria can be a new therapeutic approach to preventing the formation of kidney stones.

The Urinary Tract Microbiome in Health and Disease

CONTEXT

The urinary tract, previously considered a sterile body niche, has emerged as the host of an array of bacteria in healthy individuals, revolutionizing the urology research field.

OBJECTIVE

To review the literature on microbiome implications in the urinary tract and the usefulness of probiotics/prebiotics and diet as treatment for urologic disorders.

EVIDENCE ACQUISITION

A systematic review was conducted using PubMed and Medline from inception until July 2016. The initial search identified 1419 studies and 89 were included in this systematic review.

EVIDENCE SYNTHESIS

Specific bacterial communities have been found in the healthy urinary tract. Changes in this microbiome have been observed in certain urologic disorders such as urinary incontinence, urologic cancers, interstitial cystitis, neurogenic bladder dysfunction, sexually transmitted infections, and chronic prostatitis/chronic pelvic pain syndrome. The role of probiotics, prebiotics, and diet as treatment or preventive agents for urologic disorders requires further investigation.

CONCLUSIONS

There is a microbiome associated with the healthy urinary tract that can change in urologic disorders. This represents a propitious context to identify new diagnostic, prognostic, and predictive microbiome-based biomarkers that could be used in clinical urology practice. In addition, probiotics, prebiotics, and diet modifications appear to represent an opportunity to regulate the urinary microbiome.

PATIENT SUMMARY

We review the urinary microbiome of healthy individuals and its changes in relation to urinary disorders. The question to resolve is how we can modulate the microbiome to improve urinary tract health.

Demographic characteristics and metabolic risk factors in Croatian children with urolithiasis

The aim of this study was to assess demographic data, clinical presentation, metabolic features, and treatment in 76 children with urolithiasis presented from 2002 to 2011. Urolithiasis is responsible for 2.5/1,000 pediatric hospitalizations, with new cases diagnosed in 1.1/1,000 admissions. From the observed period, two-fold rise of incidence rate was observed. Compiling the data from other pediatric institutions in our country, we estimated present overall incidence rate in Croatia as 6.5/100,000 children under 18 years. There were 41 boys and 35 girls (ratio 1.17:1). The mean age at diagnosis was 9.7 (range 0.8-16) years and follow-up duration was 5.3 (range 1.8-10) years. Renal colic (75.0 %) and hematuria (57.89 %) were the main symptoms. In 65.78 % of children, stones were unilateral. Stones were located in kidney in 52.63 %, in the ureter in 26.32 %, and in bladder in 6.58 % cases. Stone analysis showed calcium oxalate in 75.0 % of the cases. Associated urinary tract abnormalities were found in 19.73 % children. Most common metabolic disturbances were hypercalciuria (47.37 %) and idiopathic or mild hyperoxaluria (18.42 %). Urine saturation (EQUIL2) was elevated in 61.84 % cases. Spontaneous stone evacuation occurred in 51.21 % children. Extracorporeal shock wave lithotripsy, surgical evacuation, and endoscopic removal of calculi were performed in 21.0, 6.58, and 5.26 % of cases, respectively. Follow-up conservative therapy, consisting of fluid/diet recommendations and additional potassium citrate and/or chlorothiazide in children with increased risk, was sufficient for stone recurrence prevention in 92.1 % of children. In conclusion, the study gave insight in epidemiology and metabolic disturbances of urinary stone disease in Croatian children.

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.

Heavy metal quantification in renal tissue of patients in the state of yucatan and its association with urolithiasis

A possible cause associated with urinary lithiasis (UL) is the bioaccumulation of heavy metals in the kidney. The aim of this study was to evaluate the content of Cu, Pb, and Cd in kidney tissues removed from patients with nephrological problems and associate it with UL. Samples of 50 kidney sections from patients were analyzed. Results were statistically analyzed using a fixed effects model including the overall mean, the effect of the health status of patients (with or without UL), gender (male and female), the interaction between both factors and the random error (NID  (0, σ (2))). Cu level was 8.8 ± 4.4 mg/kg (mean ± DS) and 25.5% of samples had levels above normal. Lead content in 97.9% of the samples (3.6 ± 1.5 mg/kg) was above normal. All results of Cd (13.2 ± 16.6 mg/kg) were below the maximum permissible limits. There was no difference in the amount of heavy metals on patients with or without UL (P > 0.05) nor depending on the gender (P > 0.05). It was concluded that there is no apparent relationship between a very elevated level of Cu or Pb in the kidney on the development of UL.

Impact of dietary counseling on urinary stone risk parameters in recurrent stone formers

OBJECTIVES

The aim of this study was to investigate the current impact of dietary counseling on the risk for urolithiasis.

METHODS

A retrospective cohort study of the patients treated in our stone clinics from July 2007 to February 2009 was carried out. Patients' urinary risk factors for stone disease were evaluated with pre- and postintervention 24-hour urine collections. All patients received dietary recommendations from a registered dietician at each visit.

RESULTS

One hundred thirty-seven subjects were identified and managed initially with only dietary interventions to address their urinary stone risk parameters. Average follow-up for this group was 15.19 ± 13.7 months. Subjects showed significant changes in urine volume (71.1%, 1.68 ± 0.68 to 2.59 ± 0.80 L/day, p < 0.0001), urine sodium (58.1%, 229.68 ± 72.51 to 144.65 ± 52.70 mmol/day, p < 0.0001), urine calcium (43.8%, 314.33 ± 95.75 to 216.81 ± 80.90 mg/day, p < 0.0001), urinary uric acid (50%, 0.821 ± 0.210 to 0.622 ± 0.128 g/day, p < 0.0001), urinary citrate (50.7%, 583.19 ± 330.86 to 797.36 ± 412.31, p < 0.0001), and urine oxalate (55.5%, 46.28 ± 10.31 to 32.56 ± 9.02 mg/day, p < 0.0001). The supersaturation for calcium oxalate also decreased significantly from baseline (9.34-5.03, p < 0.0001).

CONCLUSION

Urolithiasis is a multifactorial disease requiring a multidisciplinary approach. Our results support the use of dietary counseling by a registered dietician in the management of urolithiasis.

Metabolism of fructose to oxalate and glycolate

Much attention has been recently directed at fructose consumption because of its association with obesity and subsequent development of chronic diseases. It was recently reported that an increased fructose intake increases the risk of forming kidney stones. It was postulated that fructose consumption may increase urinary oxalate, a risk factor for calcium oxalate kidney stone disease. However, conflicting results have been obtained in human studies examining the relationship between fructose metabolism and oxalate synthesis. To test whether fructose intake influences urinary excretions impacting kidney stone risk, healthy subjects consumed diets controlled in their contents of fructose, oxalate, calcium, and other nutrients. Subjects consumed diets containing 4, 13, and 21% of calories as fructose in a randomized order. No changes in the excretions of oxalate, calcium, and uric acid were observed. In vitro investigations with cultured liver cells incubated with (13)C-labeled sugars indicated that neither fructose nor glucose was converted to oxalate by these cells. Fructose metabolism accounted for 12.4 ± 1.6% of the glycolate detected in the culture medium and glucose 6.4 ± 0.9%. Our results suggest that mechanisms for stone risk associated with fructose intake may lie in factors other than those affecting the major stone risk parameters in urine.

Progressive renal papillary calcification and ureteral stone formation in mice deficient for Tamm-Horsfall protein

Mammalian urine contains a range of macromolecule proteins that play critical roles in renal stone formation, among which Tamm-Horsfall protein (THP) is by far the most abundant. While THP is a potent inhibitor of crystal aggregation in vitro and its ablation in vivo predisposes one of the two existing mouse models to spontaneous intrarenal calcium crystallization, key controversies remain regarding the role of THP in nephrolithiasis. By carrying out a long-range follow-up of more than 250 THP-null mice and their wild-type controls, we demonstrate here that renal calcification is a highly consistent phenotype of the THP-null mice that is age and partially gene dosage dependent, but is gender and genetic background independent. Renal calcification in THP-null mice is progressive, and by 15 mo over 85% of all the THP-null mice develop spontaneous intrarenal crystals. The crystals consist primarily of calcium phosphate in the form of hydroxyapatite, are located more frequently in the interstitial space of the renal papillae than intratubularly, particularly in older animals, and lack accompanying inflammatory cell infiltration. The interstitial deposits of hydroxyapatite observed in THP-null mice bear strong resemblances to the renal crystals found in human kidneys bearing idiopathic calcium oxalate stones. Compared with 24-h urine from the wild-type mice, that of THP-null mice is supersaturated with brushite (calcium phosphate), a stone precursor, and has reduced urinary excretion of citrate, a stone inhibitor. While less frequent than renal calcinosis, renal pelvic and ureteral stones and hydronephrosis occur in the aged THP-null mice. These results provide direct in vivo evidence indicating that normal THP plays an important role in defending the urinary system against calcification and suggest that reduced expression and/or decreased function of THP could contribute to nephrolithiasis.

History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as 'surgical' interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis.

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.

Lemonade therapy increases urinary citrate and urine volumes in patients with recurrent calcium oxalate stone formation

OBJECTIVES

Potassium citrate is prescribed to patients with calcium oxalate (CaOx) stone formation to increase urinary citrate and pH, thus reducing CaOx crystal formation. Lemonade therapy (LT) might also increase urinary citrate and the total urine volume. We compared the effects of LT alone (group 1, n = 63) and potassium citrate plus LT (group 2, n = 37) in patients with CaOx stone formation on the urinary citrate and total urine volume to determine the efficacy of LT.

METHODS

Adult patients with CaOx stone formation and three or more clinic visits from 1996 to 2005 and three or more UroRisk profiles were included in our retrospective analysis.

RESULTS

Urinary citrate increased maximally by 203 and 346 mg/day for groups 1 and 2, respectively. The maximal total urine volume increase was 763 and 860 mL/day for groups 1 and 2, respectively. The urinary citrate and total urine volume increased sooner during follow-up for group 1. By the last clinic visit, the urinary citrate and total urine volume had decreased in both groups. However, group 1 sustained a greater total urine volume than did group 2 (2.35 +/- 0.10 standard error versus 2.17 +/- 0.12 L/day). Urinary citrate was greater in group 1 (765 +/- 56 standard error versus 548 +/- 56 mg/day for group 2), but the change from baseline to the last visit was significant (P = 0.008) only in group 2.

CONCLUSIONS

LT resulted in favorable changes in urinary citrate and total urine volume in our series. Potassium citrate with LT was more effective than LT alone at increasing urinary citrate. Because maximal changes for urinary citrate and total urine volume were achieved earlier in follow-up, individualized encouragement and motivation should be provided to patients at each visit for sustained prevention.

Adverse metabolic side effects of thiazides: implications for patients with calcium nephrolithiasis

PURPOSE

Thiazide use to prevent recurrent calcium nephrolithiasis is supported by randomized, controlled trials. Concerns regarding adverse metabolic effects of thiazides, which are also used to treat hypertension, have reemerged with analysis of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial. The risks posed by thiazide induced hyperglycemia, hyperuricemia, hypokalemia and dyslipidemia may decrease the expected cardiovascular benefit of lowering blood pressure in hypertensive patients. Whether these side effects occur and are clinically significant in nonhypertensive patients with kidney stones treated with thiazides is unclear.

MATERIALS AND METHODS

A review of the literature was performed for randomized, controlled trials with thiazides for calcium nephrolithiasis. We sought data regarding metabolic effects in this population, including hyperglycemia, hyperuricemia, hypokalemia and dyslipidemia.

RESULTS

Nine randomized, controlled trials of thiazide treatment for kidney stones were included. Mean patient age was 42 years and followup was 2.6 years. Only 2 of the 9 studies measured glucose and lipid levels, which did not significantly change with treatment. Three studies measured serum potassium and 2 showed a significant decrease. Three of the 9 studies measured serum uric acid levels, which increased in all 3. None of the trials studied the development of diabetes mellitus or cardiovascular disease.

CONCLUSIONS

There is a lack of data on the metabolic effects of thiazides used to prevent recurrent calcium nephrolithiasis. It remains unclear if metabolic effects occur and increase the risk of cardiovascular disease in otherwise healthy patients with recurrent nephrolithiasis on thiazide prophylaxis. Further research is needed to elucidate other alternatives for the treatment of recurrent nephrolithiasis.

Diagnosis and metaphylaxis of stone disease. Consensus concept of the National Working Committee on Stone Disease for the upcoming German Urolithiasis Guideline

This review draws the recent state of the art in metabolic diagnosis and metaphylaxis of stone disease. It is the basis for the consensus approval with the other medical societies and institutions in Germany involved in the guideline process of the new "Urolithiasis Guideline". The German Working Committee on Stone Disease reviewed critically the current literature in the field of urolithiasis-including the existing German and EAU-Guidelines as well as the Conference Book of the First International Consultation on Stone Disease. As far as possible the references were rated according to the EBM criteria. On this basis the expert group discussed all pathways and statements regarding the management of stone disease. The present review coincides with the consented guideline draft of the German Working Committee on Stone Disease. Occurrence of stone disease in the western world increases seriously. Modern lifestyle, dietary habits and overweight-problems of the affluent societies-emerge to be the important promoters of the "stone-boom" in the new millennium. This even affects children, whose stone prevalence is otherwise significantly less than that of adults. Criteria for the high risk group of stone formers were clearly defined. A diagnostic standard is formulated for the basic and the elaborate metabolic evaluation of a stone patient. Approximately 75% of all stone patients could anticipate stone recurrence with elementary reorientation of their lifestyle and dietary habits, summarized as general metaphylaxis. About 25% of the stone formers require additional pharmacological intervention to normalize their individual biochemical risk, precisely compiled for each stone type as specific metaphylaxis.

Effect of an isotonic rehydration sports drink and exercise on urolithiasis in rats

The objective of the present study was to evaluate the role of physical exercise as well as the influence of hydration with an isotonic sports drink on renal function in male Wistar rats. Four groups were studied over a period of 42 days: 1) control (N = 9); 2) physical exercise (Exe, N = 7); 3) isotonic drink (Drink, N = 8); 4) physical exercise + isotonic drink (Exe + Drink, N = 8). Physical exercise consisted of running on a motor-driven treadmill for 1 h/day, at 20 m/min, 5 days a week. The isotonic sports drink was a commercial solution used by athletes for rehydration after physical activity, 2 ml administered by gavage twice a day. Urine cultures were performed in all animals. Twenty-four-hour urine samples were collected in metabolic cages at the beginning and at the end of the protocol period. Urinary and plasma parameters (sodium, potassium, urea, creatinine, calcium) did not differ among groups. However, an amorphous material was observed in the bladders of animals in the Exe + Drink and Drink groups. Characterization of the material by Western blot revealed the presence of Tamm-Horsfall protein and angiotensin converting enzyme. Physical exercise and the isotonic drink did not change the plasma or urinary parameters measured. However, the isotonic drink induced the formation of intravesical matrix, suggesting a potential lithogenic risk.

Gut-inhabiting bacterium Oxalobacter formigenes: role in calcium oxalate urolithiasis

Oxalate plays a crucial role in the formation of most renal stones. Oxalate is a common constituent of most diets and a byproduct of metabolism, and if it is not sufficiently degraded, it may accumulate. In humans, gut bacteria degrade 70 to 100 mg of oxalate per day. Oxalobacter formigenes is a gram-negative, obligately anaerobic, rod-shaped bacterium with an absolute requirement for oxalate. Although not present in the gut at birth, it quickly colonizes most children, and there is epidemiologic evidence that its absence is a risk factor in calcium oxalate stone formation. We review the metabolism, genetics, and identification of this organism and its possible therapeutic role in recurrent stone-forming patients.

The effect of oral administration of calcium and magnesium on intestinal oxalate absorption in humans

Calcium oxalate (CaOx) urolithiasis is the most common urinary stone disease (70-75 % of all stones consist of CaOx in countries with western diet). Oxalate is the most lithogenic substance in CaOx crystallisation in urine. Oxalate is either synthesized within the body or absorbed from food. As oxalate is not metabolized in the human body, it appears unchanged in urine. Conventional analysis methods cannot distinguish between endogenous and exogenous oxalate. Our [13C2]oxalate absorption test enabled measurement of intestinal oxalate absorption and quantification of the influence of Ca- and Mg-supplementation on it. The effects of the oral administration of these supplements were compared in order to obtain valid data for recommendations for CaOx urolithiasis patients. A 10 mmol supplement of both ions decreased the oxalate absorption significantly, calcium being more than twice as effective.

Determination of the calcium oxalate crystallization risk from urine samples: the BONN Risk Index in comparison to other risk formulas

PURPOSE

Regular risk evaluation and risk monitoring during stone therapy are recommended measures to ensure reduction of recurrence of crystal formation. This strategy optimizes the patient treatment by a more individual approach and decreases expensive over treatment. We evaluated the BONN Risk Index (BRI) through data actualization and evaluation refinement. The BRI was compared with the most common methods of risk evaluation, namely calculation of relative urinary calcium oxalate (CaOx) supersaturation (RS) and of the urine activity product (AP)CaOx index to estimate the urine AP with respect to CaOx.

MATERIALS AND METHODS

A total of 201, 12 and 24-hour urine samples were collected from 95 healthy volunteers and from 106 CaOx stone formers. Crystallization experiments following the BRI method were performed. RS and APCaOx were calculated from urinalysis. Data were indexed and individually grouped into 8 classes, and frequency distributions were plotted. A calculation scheme for the BRI based estimation of the statistical probability of a clinically healthy person being a (still nondetected) CaOx stone former is provided.

RESULTS

Logarithmically arranged BRI groups from healthy subject and patient data showed Gaussian frequency distributions. Compared with RS and APCaOx BRI allowed optimum distinction between healthy subjects and stone formers. The healthy subject probability of already being a CaOx stone former strongly increased with increasing BRI.

CONCLUSIONS

The BRI for evaluating CaOx crystallization risk allows reliable distinction between healthy subjects and CaOx stone formers. Although RS and APCaOx require much more analytical efforts for determination, their results do not show higher reliability.

Medical management of calcium oxalate urolithiasis

Dietary modifications and medical therapy can reduce the risk of urinary stone formation. Using the described stepwise approach, the medical management of stone disease should become a less daunting task for physicians. Unfortunately, the optimal medical and dietary management of urolithiasis remains uncertain and recurrent stone disease remains a significant cause of morbidity. Approaches to diagnosis and medical management have improved considerably in the last decade and it is hoped that well-designed studies in the near future will help further optimize management.

The relative effects of supplemental dietary calcium and oxalate on urine composition and calcium oxalate relative supersaturation in healthy adult dogs

The aim of this study was to establish the relative effects of dietary calcium and oxalate (in the form of oxalic acid) on the composition of urine produced by healthy adult Cairn Terriers and Miniature Schnauzers. A nutritionally complete dry dog food was fed to 7 dogs (4 Cairn terriers and 3 Miniature schnauzers) for 24 weeks. The dogs were fed the diet alone, or supplemented with six different combinations of dietary calcium (as carbonate and sulphate) and oxalate (as oxalic acid) commonly found in dry commercially prepared dog foods. Urine pH, volume, specific gravity, and concentrations of 12 analytes were measured for each dog; urinary relative supersaturation (RSS) with calcium oxalate (CaOx) was calculated from these values. The effects of supplemental calcium and oxalate were established using two-way analysis of variance and multiple range tests (least significant difference); P<0.05 was considered significant. The lowest level of dietary calcium and oxalate resulted in the lowest CaOx RSS. The high calcium, low oxalate diet resulted in the highest CaOx RSS, a low calcium diet with increased dietary oxalate also tended to increase CaOx RSS although results were highly variable. Urinary calcium concentration increased significantly with dietary calcium; urinary oxalate increased, although inconsistently, with dietary oxalic acid only when dietary calcium was low. Measures to reduce both calcium and oxalate should be considered when implementing dietary changes to reduce the risk of calcium oxalate formation in dogs. A reduction in dietary calcium without a concomitant decrease in dietary oxalate may increase the risk of CaOx crystallisation in susceptible dogs.

The urinary response to an oral oxalate load in recurrent calcium stone formers

PURPOSE

Dietary oxalate may contribute up to 50% to 80% of the oxalate excreted in urine. We studied the urinary response to an oral oxalate load in male and female idiopathic recurrent calcium oxalate stone formers with and without mild hyperoxaluria to evaluate the potential pathophysiological significance of dietary oxalate.

MATERIALS AND METHODS

A total of 60 recurrent calcium stone formers underwent an oral oxalate load test. Urine samples were obtained after an overnight fast. Each patient then received an oral oxalate load (5 mM. sodium oxalate dissolved in 250 ml. distilled water) and 3, 2-hour urine samples were obtained 2, 4 and 6 hours after the oxalate load. We compared the response to the oxalate load in patients with and without mild hyperoxaluria, and in male and female patients without hyperoxaluria.

RESULTS

The peak urinary response occurred 4 hours after the oral oxalate load in all patients. Those with mild hyperoxaluria had a mean fasting urinary oxalate-to-creatinine ratio +/- SE of 0.027 +/- 0.003 and a mean peak urinary oxalate-to-creatinine ratio of 0.071 +/- 0.006. In comparison, patients with normal oxalate excretion had a fasting and peak urinary oxalate-to-creatinine ratio of 0.018 +/- 0.001 and 0.056 +/- 0.004, respectively (p <0.05). The mean 6-hour increment for urinary oxalate excretion after the oxalate load for patients with hyperoxaluria versus those with normal urinary oxalate excretion was 17.2 +/- 1.9 versus 12.1 +/- 0.98 mg. (p <0.05). In the subset of patients with normal urinary oxalate excretion mean 6-hour cumulative urinary oxalate excretion was 16.8 +/- 1.3 and 13.3 +/- 1.4 mg. in males and females, respectively (p not significant).

CONCLUSIONS

Recurrent calcium stone formers with mild hyperoxaluria have higher fasting urinary oxalate and an exaggerated urinary response to an oral oxalate load compared with recurrent calcium stone formers with normal urinary oxalate excretion. Men and women stone formers without hyperoxaluria excrete similar fractions of an oral oxalate load. Increased gastrointestinal absorption and renal excretion of dietary oxalate may be a significant pathophysiological mechanism of stone formation in patients with mild hyperoxaluria.

Epidemiology and medical management of stone disease

Recurrent stone formation in the urinary tract is a common and important problem that must be considered in daily urological practice. With a prevalence of> 10% and an expected recurrence rate of approximately 50%, stone disease has an important effect on the healthcare system. It is generally agreed that patients with uric acid/urate, cystine or infection stones always should be treated pharmacologically. For calcium stone formers the treatment should be chosen according to the severity of the disease. Recurrence in patients with calcium-stone disease can be prevented with general or specific dietary and drinking advice, and with pharmacological therapy. For idiopathic calcium stone formers the most convincing therapeutic effects have been reported with thiazide and alkaline citrate.

Comparison of laser-probe and photometric determination of the urinary crystallization risk of calcium oxalate

A variety of equipment is used for the observation of precipitation processes which occur in urinary samples. The Bonn-Risk-Index, a measure of the calcium oxalate crystallization risk of human urine, has been developed with the use of an in-line laser-probe gauge. For basic research or in clinical laboratories, however, this instrument, which fulfills industrial requirements for the evaluation of particle size distributions, is not widely available. The evaluation of an alternative method to determine the Bonn-Risk-Index based on a more commonly available apparatus would therefore be useful. In vitro crystallization experiments with 124 native urine samples from stone-forming and non-stone forming individuals were performed in order to determine their crystallization risk according to the Bonn-Risk-Index approach. The onset of an induced urinary crystallization was detected by simultaneous sample monitoring with an in-line laser-probe and a conventional dip-in photometer. A decrease of the sample's relative light transmissivity from initially 100% to 98% was assumed to be a reliable photometer-based criterion to indicate that crystallization actually began. The laser-probe signal was set as the reference measure. Linear regression analysis of the results of the laser-probe and the photometer-based Bonn-Risk-Index determinations reveals a significant and close correlation between the two measures. Method comparison by statistical evaluation shows i) that no significant deviation from linearity exists and ii) that both methods are statistically identical. The differences in the results are small enough to be confident that the photometer can be used in place of the laser-probe for clinical purposes. The photometer is a reliable, easy-to-use and cost-effective method for the determination of a triggered crystallization event in a urine sample. The assumed 98% criterion allows the determination of the Bonn-Risk-Index with adequate accuracy.

Reduction of oxaluria after an oral course of lactic acid bacteria at high concentration

BACKGROUND

Hyperoxaluria is a major risk factor for renal stones, and in most cases, it appears to be sustained by increased dietary load or increased intestinal absorption. Previous studies have shown that components of the endogenous digestive microflora, in particular Oxalobacter formigenes, utilize oxalate in the gut, thus limiting its absorption. We tested the hypothesis of whether oxaluria can be reduced by means of reducing intestinal absorption through feeding a mixture of freeze-dried lactic acid bacteria.

METHODS

Six patients with idiopathic calcium-oxalate urolithiasis and mild hyperoxaluria (>40 mg/24 h) received daily a mixture containing 8 x 10(11) freeze-dried lactic acid bacteria (L. acidophilus, L. plantarum, L. brevis, S. thermophilus, B. infantis) for four weeks. The 24-hour urinary excretion of oxalate was determined at the end of the study period and then one month after ending the treatment. The ability of bacteria to degrade oxalate and grow in oxalate-containing media, and the gene expression of Ox1T, an enzyme that catalyzes the transmembrane exchange of oxalate, also were investigated.

RESULTS

The treatment resulted in a great reduction of the 24-hour excretion of oxalate in all six patients enrolled. Mean levels +/- SD were 33.5 +/- 15.9 mg/24 h at the end of the study period and 28.3 +/- 14.6 mg/24 h one month after treatment was interrupted compared with baseline values of 55.5 +/- 19.6 mg/24 h (P < 0.05). The treatment was associated with a strong reduction of the fecal excretion of oxalate in the two patients tested. Two bacterial strains among those used for the treatment (L. acidophilus and S. thermophilus) proved in vitro to degrade oxalate effectively, but their growth was somewhat inhibited by oxalate. One strain (B. infantis) showed a quite good degrading activity and grew rapidly in the oxalate-containing medium. L. plantarum and L. brevis showed a modest ability to degrade oxalate even though they grew significantly in oxalate-containing medium. No strain expressed the Ox1T gene.

CONCLUSIONS

The urinary excretion of oxalate, a major risk factor for renal stone formation and growth in patients with idiopathic calcium-oxalate urolithiasis, can be greatly reduced with treatment using a high concentration of freeze-dried lactic acid bacteria. We postulate that the biological manipulation of the endogenous digestive microflora can be a novel approach for the prevention of urinary stone formation.

Prevention of nephrolithiasis

The high incidence of recurrence after an initial stone event underscores the need for an effective medical prophylactic program. Dietary modification and drug therapies have long been advocated to reduce the likelihood of stone recurrence. While the efficacy of a high fluid intake has been validated in a randomized trial, the benefit of other dietary measures is based on modulation of urinary stone risk factors and outcomes derived from observational studies. Several drug therapies have been evaluated in a limited number of prospective, randomized trials and efficacy has been demonstrated for thiazides, allopurinol and alkali citrate in some populations of recurrent stone formers. The role of selective versus nonselective therapy for stone prevention awaits further study.