Contrasting effects of potassium citrate and sodium citrate therapies on urinary chemistries and crystallization of stone-forming salts

[Hyperuricemia and uro-nephrological disorders]

Hyperuricemia is a specific risk factor for cardiovascular morbidity and mortality. Uric acid lithiasis is urological symptom of hyperuricemia. In case of uric acid lithiasis, you must search a metabolic syndrome, an insulin resistance, a type 2 diabetes. Chronic tubular interstitial nephropathy is the renal disease of hyperuricemia. Hyperuricemia is a specific risk factor for chronic renal failure. Metabolism of uric acid involves the uromodulin.

Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality

Background

Modern diets have been suggested to increase systemic acid load and net acid excretion. In response, alkaline diets and products are marketed to avoid or counteract this acid, help the body regulate its pH to prevent and cure disease. The objective of this systematic review was to evaluate causal relationships between dietary acid load and osteoporosis using Hill's criteria.

Methods

Systematic review and meta-analysis. We systematically searched published literature for randomized intervention trials, prospective cohort studies, and meta-analyses of the acid-ash or acid-base diet hypothesis with bone-related outcomes, in which the diet acid load was altered, or an alkaline diet or alkaline salts were provided, to healthy human adults. Cellular mechanism studies were also systematically examined.

Results

Fifty-five of 238 studies met the inclusion criteria: 22 randomized interventions, 2 meta-analyses, and 11 prospective observational studies of bone health outcomes including: urine calcium excretion, calcium balance or retention, changes of bone mineral density, or fractures, among healthy adults in which acid and/or alkaline intakes were manipulated or observed through foods or supplements; and 19 in vitro cell studies which examined the hypothesized mechanism. Urine calcium excretion rates were consistent with osteoporosis development; however calcium balance studies did not demonstrate loss of whole body calcium with higher net acid excretion. Several weaknesses regarding the acid-ash hypothesis were uncovered: No intervention studies provided direct evidence of osteoporosis progression (fragility fractures, or bone strength as measured using biopsy). The supporting prospective cohort studies were not controlled regarding important osteoporosis risk factors including: weight loss during follow-up, family history of osteoporosis, baseline bone mineral density, and estrogen status. No study revealed a biologic mechanism functioning at physiological pH. Finally, randomized studies did not provide evidence for an adverse role of phosphate, milk, and grain foods in osteoporosis.

Conclusions

A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health.

Nephrolithiasis-associated bone disease: pathogenesis and treatment options

Nephrolithiasis remains a formidable health problem in the United States and worldwide. A very important but underaddressed area in nephrolithiasis is the accompanying bone disease. Epidemiologic studies have shown that osteoporotic fractures occur more frequently in patients with nephrolithiasis than in the general population. Decreased bone mineral density and defects in bone remodeling are commonly encountered in patients with calcium nephrolithiasis. The pathophysiologic connection of bone defects to kidney stones is unknown. Hypercalciuria and hypocitraturia are two important risk factors for stone disease, and treatments with thiazide diuretics and alkali, respectively, have been shown to be useful in preventing stone recurrence in small prospective trials. However, no studies have examined the efficacy of these agents or other therapies in preventing continued bone loss in calcium stone formers. This manuscript reviews the epidemiology, pathophysiology, and potential treatments of bone disease in patients with nephrolithiasis.

Effects of gamma radiation on solid trisodium citrate dihydrate: radical kinetics, radiosensitivity and dosimetry

In the present work, radiosensitivity and dosimetric potential of solid trisodium citrate dihydrate (SC) were explored through a detailed electron spin resonance (ESR) study performed at various temperatures. Irradiated SC was observed to exhibit an ESR spectrum consisting of many intense and weak resonance lines spread over a magnetic field range of 7 mT and centered at g = 2.0039. An evaluation technique based on the variations of the characteristic resonance line intensities and the spectrum area under different experimental conditions was adopted, to determine the spectroscopic, kinetic and dosimetric features of radical species responsible for the observed experimental ESR spectrum. Radicals exhibiting similar ESR characteristics to those reported in the literature for irradiated tricarboxilic acids and their organic compounds were shown to be also produced in gamma-irradiated SC.

Pharmacotherapy of urolithiasis: evidence from clinical trials

Urolithiasis is a worldwide problem with significant health and economic burdens. Medical therapy that alters the course of stone disease has enormous medical and financial impact. Urolithiasis is a final manifestation of a broad range of etiologies and pathogenesis. The modest progress in understanding the pathophysiology has hampered successful development of targeted therapy. Current regimens are based mostly on rational alteration of urinary biochemistry and physical chemistry to lower the risk of precipitation. In terms of pharmacotherapy, there are drugs to successfully improve hypercalciuria, hypocitraturia, aciduria, hyperuricosuria, and hypercystinuria. These agents have been proven to be effective in randomized controlled trials in improving urinary biochemical and physicochemical risk factors, as well as clinical outcomes. Although our current regimens have clearly improved the management and lives of stone formers, there are still clearly identifiable immense voids in the knowledge of pathophysiology of stone disease that can be filled with combined basic science and clinical studies.

Urolithiasis on the ketogenic diet with concurrent topiramate or zonisamide therapy

Children with refractory epilepsy who are co-treated with the ketogenic diet (KD) and carbonic anhydrase inhibitor (CA-I) anti-epileptic medications including topiramate (TPM) and zonisamide (ZNS) are at risk for urolithiasis. Retrospective chart review of all children treated with ketogenic therapy at our institution was performed in order to estimate the minimal risk of developing signs or symptoms of stone disease. Children (N=93) were classified into groups according to KD+/-CA-I co-therapy. Fourteen patients had occult hematuria or worse, including 6 with radiologically confirmed stones. Three of 6 calculi developed in the KD+ZNS group of 17 patients who were co-treated for a cumulative total of 97 months (3.1 stones per 100 patient months). One confirmed stone was in the KD+TPM group of 22 children who were co-treated for a cumulative total of 263 months (0.4 stones per 100 patient months). All six patients had at least three of five biochemical risk factors including metabolic acidosis, concentrated urine, acid urine, hypercalciuria and hypocitraturia. Standard of care interventions to minimize hypercalciuria, crystalluria and stone formation used routinely by pediatric nephrologists should also be prescribed by neurologists treating patients with combination anti-epileptic therapy. Non-fasting KD initiation, fluid liberalization, potassium citrate prophylaxis as well as regular laboratory surveillance are indicated in this high risk population.

Hypocitraturia and hyperoxaluria after Roux-en-Y gastric bypass surgery

PURPOSE

Roux-en-Y gastric bypass surgery is associated with an increased risk of nephrolithiasis but obesity itself is a known risk factor for kidney stones. To assess the mechanism(s) predisposing to nephrolithiasis after Roux-en-Y gastric bypass we compared urinary tract stone risk profiles in patients who underwent the procedure and normal obese individuals.

MATERIALS AND METHODS

In this cross-sectional study urine and serum biochemistry was evaluated in 19 nonstone forming patients after Roux-en-Y gastric bypass and in 19 gender, age and body mass index matched obese controls without a history of nephrolithiasis.

RESULTS

Compared with obese controls surgical patients had significantly higher mean +/- SD urine oxalate (45 +/- 21 vs 30 +/- 11 mg daily, p = 0.01) and lower urine citrate (358 +/- 357 vs 767 +/- 307 mg daily, p <0.01). The prevalence of hyperoxaluria (47% vs 10.5%, p = 0.02) and hypocitraturia (63% vs 5%, p <0.01) was significantly higher in surgical patients, who also had significantly lower urine calcium than obese controls (115 +/- 93 vs 196 +/- 123 mg daily, p = 0.03). The calcium oxalate urine relative supersaturation ratio was not significantly different between the 2 groups.

CONCLUSIONS

Almost half of patients with Roux-en-Y gastric bypass without a history of nephrolithiasis showed hyperoxaluria or hypocitraturia. This prevalence was significantly higher than in body mass index matched controls. These risk factors were negated by lower urine calcium excretion in patients with Roux-en-Y gastric bypass.

Demographic, dietary, and urinary factors and 24-h urinary calcium excretion

BACKGROUND AND OBJECTIVES

Higher urinary calcium is a risk factor for nephrolithiasis. This study delineated associations between demographic, dietary, and urinary factors and 24-h urinary calcium.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Cross-sectional studies were conducted of 2201 stone formers (SF) and 1167 nonstone formers (NSF) in the Health Professionals Follow-up Study (men) and Nurses' Health Studies I and II (older and younger women).

RESULTS

Median urinary calcium was 182 mg/d in men, 182 mg/d in older women, and 192 mg/d in younger women. Compared with NSF, urinary calcium as a fraction of calcium intake was 33 to 38% higher in SF (P values < or =0.01). In regression analyses, participants were combined because associations with urinary calcium were similar in each cohort and in SF and NSF. After multivariate adjustment, participants in the highest quartile of calcium intake excreted 18 mg/d more urinary calcium than those in the lowest (P trend =0.01). Caffeine and family history of nephrolithiasis were positively associated, whereas urinary potassium, thiazides, gout, and age were inversely associated, with urinary calcium. After multivariate adjustment, participants in the highest quartiles of urinary magnesium, sodium, sulfate, citrate, phosphorus, and volume excreted 71 mg/d, 37 mg/d, 44 mg/d, 61 mg/d, 37 mg/d, and 24 mg/d more urinary calcium, respectively, than participants in the lowest (P values trend < or =0.01).

CONCLUSIONS

Intestinal calcium absorption and/or negative calcium balance is greater in SF than NSF. Higher calcium intakes at levels typically observed in free-living individuals are associated with only small increases in urinary calcium.

Recent advances in the pathophysiology of nephrolithiasis

Over the past 10 years, major progress has been made in the pathogenesis of uric acid and calcium stones. These advances have led to our further understanding of a pathogenetic link between uric acid nephrolithiasis and the metabolic syndrome, the role of Oxalobacter formigenes in calcium oxalate stone formation, oxalate transport in Slc26a6-null mice, the potential pathogenetic role of Randall's plaque as a precursor for calcium oxalate nephrolithiasis, and the role of renal tubular crystal retention. With these advances, we may target the development of novel drugs including (1) insulin sensitizers; (2) probiotic therapy with O. formigenes, recombinant enzymes, or engineered bacteria; (3) treatments that involve the upregulation of intestinal luminal oxalate secretion by increasing anion transporter activity (Slc26a6), luminally active nonabsorbed agents, or oxalate binders; and (4) drugs that prevent the formation of Randall's plaque and/or renal tubular crystal adhesions.

Can lemon juice be an alternative to potassium citrate in the treatment of urinary calcium stones in patients with hypocitraturia? A prospective randomized study

To investigate that lemon juice could be an alternative to potassium citrate in the treatment of urinary calcium stones in patients with hypocitraturia, 30 patients with hypocitraturic urinary calcium stones were enrolled into study. The patients were divided into three groups equally. Exactly 60 mEq/day fresh lemon juice ( approximately 85 cc/day) and potassium citrate (60 mEq/day) were given to the patients of first and second group, respectively. Dietary recommendations were made for the third group. Blood and 24-h urine tests were performed before treatment and repeated 3 months later. The differences between demographic datas of groups were not significant. There was no significant difference between values of blood tests performed before and after treatment in all groups. Statistically significant differences were found between pre- and post-treatment urine values in each group. Although there was no significant difference between pre-treatment citrate levels of the groups. A significant difference was found between post-treatment citrate levels of the groups. There was 2.5-, 3.5- and 0.8-fold increase in urinary citrate level of lemon juice, potassium citrate and dietary recommendation groups, respectively. Urinary calcium level was decreased only in lemon juice and potassium citrate groups after treatment. While there was no significant difference between pre- and post-treatment urinary oxalate levels in all groups, a significant decrease in urinary uric acid levels was determined in all groups. We suggest that lemon juice can be an alternative in the treatment of urinary calcium stones in patients with hypocitraturia. Additionally, dietary recommendations can increase effectiveness of the treatment.

Assessment of citrate concentrations in citrus fruit-based juices and beverages: implications for management of hypocitraturic nephrolithiasis

BACKGROUND AND PURPOSE

Dietary intake of citrate in the form of citrus juices (eg, lemonade, orange juice) will enhance urinary citrate excretion, a valuable benefit for patients with hypocitraturic calcium oxalate nephrolithiasis. While information on citrate concentrations in select citrus juices is available, data on citrate concentrations of commercially available beverages (juice and otherwise) are limited. Using nuclear magnetic resonance spectroscopy (1H NMR), we report citrate concentrations of several beverages to help guide dietary recommendations aimed at increasing urinary citrate excretion and correcting hypocitraturia.

METHODS

Citrate concentrations of a squeezed lemon, several fruit juices, and common beverages were measured using 1H NMR. Spectra for each sample were obtained in duplicate; citrate peak was identified, measured, and quantified and compared with the citrate concentration in the juice of 1 medium lemon.

RESULTS

Quantitative analysis revealed the highest concentration of citrate was in grapefruit juice (64.7 mmol/L), followed in decreasing concentrations by lemon juice (47.66 mmol/L), orange juice (47.36 mmol/L), pineapple juice (41.57 mmol/L), reconstituted lemonade (38.65 mmol/L), lemonade flavored Crystal Light (38.39 mmol/L), ready to consume not from concentrate lemonade (38.24 mmol/L), cranberry juice (19.87 mmol/L), lemon-flavored Gatorade (19.82 mmol/L), homemade lemonade (17.42 mmol/L), Mountain Dew (8.84 mmol/L), and Diet 7Up (7.98 mmol/L), respectively.

CONCLUSIONS

According to 1H NMR, all of the tested "natural" citrus juices have high concentrations of citrate (38.3-67.4 mmol/L), with grapefruit juice having the highest concentration of the beverages chosen. Lemonade flavored Crystal Light had the highest concentration of citrate in the nonjuice category of tested beverages. In patients with mild to moderate hypocitraturia, dietary supplementation with citrus-based juices may be an effective alternative to medical management while not requiring large serving sizes. Further prospective studies are warranted to evaluate the clinical significance of these findings.

Meta-analysis of the quantity of calcium excretion associated with the net acid excretion of the modern diet under the acid-ash diet hypothesis

BACKGROUND

The acid-ash diet hypothesis of osteoporosis suggests that acid from the modern diet causes a demineralization of the skeleton, and mobilized bone calcium is excreted. A systematic approach has not been used to summarize the findings of the numerous studies about the hypothesis.

OBJECTIVES

The purpose of this meta-analysis was to estimate the quantity of net acid excretion and calciuria associated with the modern diet, to assess the association between acid excretion and calcium excretion, and to assess the influence of urine preservatives on calcium measurement.

DESIGN

We systematically searched for trials of the acid-ash hypothesis and conducted a meta-analysis.

RESULTS

Twenty-five of 105 studies met the inclusion criteria. The estimated quantity of net acid excretion from the weighted average of the control diets from 11 studies was 47 mEq/d. The increase in urinary calcium with a change in renal net acid excretion depended on whether the urine was acidic or alkaline (P < 0.001). A significant linear relation was observed between net acid excretion and calcium excretion for both acidic and alkaline urine (P < 0.001). The estimated change in urine calcium associated with a change of 47 mEq of net acid excretion in acidic urine was 1.6 mmol/d (66 mg/d) of calcium.

CONCLUSION

Evidence suggests a linear association between changes in calcium excretion in response to experimental changes in net acid excretion. However, this finding is not evidence that the source of the excreted calcium is bone or that this calciuria contributes to the development of osteoporosis.

Nutrition: its role in bone health

At a given age, bone mass is determined by the amount of bone accumulated at the end of skeletal growth (the so-called peak bone mass), and by the amount of bone lost subsequently. Nutritional intake is an environmental factor that influences both bone capital accumulation, which is fully achieved by the end of the second decade of life, and bone loss, which occurs during the second half of existence. Nutrients may act directly by modifying bone turnover, or indirectly via changes in calciotropic hormone secretion. The study of the association between nutrition and a bone phenotypic expression may provide inconsistent results, in part because of the low accuracy and reproducibility of the various tools used to assess dietary intakes. Sufficient dietary calcium and protein are necessary for bone health during growth as well as in the elderly.

New methods of assessing crystal growth and saturation of brushite in whole urine: effect of pH, calcium and citrate

PURPOSE

Brushite crystallization might be important in stone formation and prevention. To explore this question new methods for the saturation and crystal growth of brushite were devised that are applicable to whole urine without any computer program.

MATERIALS AND METHODS

The saturation value (concentration-to-product ratio) was determined by dividing the molar concentration product of Ca ([Ca]) and phosphate ([P]), that is [Ca] x [P], of original urine by the steady state solubility obtained after incubating with an excess of brushite (10 mg/ml) for 5 hours. Crystal growth was measured from the depletion of filtrate ([Ca] x [P]) 3 hours after seeding with brushite (0.25 mg/ml). To test the effect of pH, Ca and citrate the saturation value and crystal growth were determined in 24-hour urine samples from 4 normal volunteers and 2 stone formers, and modified artificially to produce 4 ranges of pH, Ca and citrate by adding acid, base, Ca or citrate.

RESULTS

The saturation value and crystal growth of brushite increased with an increase in pH or the Ca concentration but they decreased when the citrate concentration increased. The saturation value correlated strongly with crystal growth.

CONCLUSIONS

The new methods of brushite saturation value and crystal growth should help discern how abnormalities in urinary pH, Ca and citrate interact to influence the formation of Ca stones in cases of distal renal tubular acidosis and alkali therapy.

Beneficial effects of potassium on human health

Until recently, humans consumed a diet high in potassium. However, with the increasing consumption of processed food, which has potassium removed, combined with a reduction in the consumption of fruits and vegetables, there has been a large decrease in potassium intake which now, in most developed countries, averages around 70 mmol day-1, i.e. only one third of our evolutionary intake. Much evidence shows that increasing potassium intake has beneficial effects on human health. Epidemiological and clinical studies show that a high-potassium diet lowers blood pressure in individuals with both raised blood pressure and average population blood pressure. Prospective cohort studies and outcome trials show that increasing potassium intake reduces cardiovascular disease mortality. This is mainly attributable to the blood pressure-lowering effect and may also be partially because of the direct effects of potassium on the cardiovascular system. A high-potassium diet may also prevent or at least slow the progression of renal disease. An increased potassium intake lowers urinary calcium excretion and plays an important role in the management of hypercalciuria and kidney stones and is likely to decrease the risk of osteoporosis. Low serum potassium is strongly related to glucose intolerance, and increasing potassium intake may prevent the development of diabetes that occurs with prolonged treatment with thiazide diuretics. Reduced serum potassium increases the risk of lethal ventricular arrhythmias in patients with ischaemic heart disease, heart failure and left ventricular hypertrophy, and increasing potassium intake may prevent this. The best way to increase potassium intake is to increase the consumption of fruits and vegetables.

Metabolic syndrome and uric acid nephrolithiasis

The metabolic syndrome describes a cluster of metabolic features that increases the risk for type 2 diabetes mellitus and cardiovascular disease. The prevalence of uric acid nephrolithiasis is higher among stone-forming patients with features of the metabolic syndrome such as obesity and/or type 2 diabetes mellitus. The major determinant in the development of idiopathic uric acid stones is an abnormally low urinary pH. The unduly urinary acidity in uric acid stone formers increasingly is recognized to be one of the features observed in the metabolic syndrome. Two major abnormalities have been implicated to explain this overly acidic urine: (1) increased net acid excretion, and (2) impaired buffering caused by defective urinary ammonium excretion, with the combination resulting in abnormally acidic urine. New information is emerging linking these defects to changes in insulin signaling in the kidney. This article reviews the epidemiologic and metabolic studies linking uric acid nephrolithiasis with the metabolic syndrome, and examines the potential mechanisms underlying the unduly acidic urine in these conditions.

Mechanism of urinary calcium regulation by urinary magnesium and pH

Urinary magnesium and pH are known to modulate urinary calcium excretion, but the mechanisms underlying these relationships are unknown. In this study, the data from 17 clinical trials in which urinary magnesium and pH were pharmacologically manipulated were analyzed, and it was found that the change in urinary calcium excretion is directly proportional to the change in magnesium excretion and inversely proportional to the change in urine pH; a regression equation was generated to relate these variables (R(2) = 0.58). For further exploration of these relationships, intravenous calcium chloride, magnesium chloride, or vehicle was administered to rats. Magnesium infusion significantly increased urinary calcium excretion (normalized to urinary creatinine), but calcium infusion did not affect magnesium excretion. Parathyroidectomy did not prevent this magnesium-induced hypercalciuria. The effect of magnesium loading on calciuria was still observed after treatment with furosemide, which disrupts calcium and magnesium absorption in the thick ascending limb, suggesting that the effect may be mediated by the distal nephron. The calcium channel TRPV5, normally present in the distal tubule, was expressed in Xenopus oocytes. Calcium uptake by TRPV5 was directly inhibited by magnesium and low pH. In summary, these data are compatible with the hypothesis that urinary magnesium directly inhibits renal calcium absorption, which can be negated by high luminal pH, and that this regulation likely takes place in the distal tubule.

Increased propensity for calcium phosphate kidney stones with topiramate use

Topiramate (TPM) is a neuromodulatory agent that was initially approved as an antiepileptic drug and is increasingly used in the treatment of a number of neurological and metabolic disorders. Among its various pharmacological actions, TPM has been shown to inhibit the activity of specific carbonic anhydrase enzymes in the kidney. This action is associated with the development of metabolic acidosis, hypocitraturia, hypercalciuria and elevated urine pH, leading to an increased risk of kidney stone disease. Despite the cautionary note in the package insert of TPM, the extent of these complications has not been fully explored. Few prescribing physicians are aware of these complications, underscoring the need for improved surveillance. Because the drug is among the most frequently prescribed agents in the US, more controlled studies are required to determine the prevalence of kidney stone disease among TPM users, and the optimal approach to prevent and treat nephrolithiasis in these individuals.

Uric Acid Nephrolithiasis

Uric acid nephrolithiasis may be the final manifestation of various pathophysiological processes. Recent advances in renal urate transport have elucidated mechanisms by which hyperuricosuria occurs. However, in most uric acid stone formers the primary pathophysiologic defect is an excessively acidic urine pH rather than hyperuricosuria. Insulin resistance may contribute to the development of acidic urine by augmenting endogenous acid production and decreasing renal ammonium excretion. Medical management strategies focus primarily on alkali treatment or decreasing hyperuricosuria.

Efficacy of expulsive therapy using nifedipine or tamsulosin, both associated with ketoprofene, after shock wave lithotripsy of ureteral stones

Extracorporeal shock wave lithotripsy (ESWL) is currently considered one of the main treatments for ureteral stones. Some studies have reported the effectiveness of pharmacologic therapies (calcium antagonists or alpha-blockers) in facilitating ureteral stone expulsion after ESWL. We prospectively evaluated the efficacy, after ESWL, of nifedipine on upper-middle ureteral stones, and tamsulosin on lower ureteral stones, both associated to ketoprofene as anti-edema agent. From January 2003 to March 2005 we prospectively evaluated 113 patients affected by radiopaque or radiolucent ureteral stones. Average stone size was 10.16 +/- 2.00 mm (range 6-14 mm). Thirty-seven stones were located in the upper ureter, 27 in the middle ureter, and 49 in the lower ureter. All patients received a single session of ESWL (mean number of shock waves: 3,500) by means of a Dornier Lithotripter S (mean energy power for each treatment: 84%). Both ultrasound and X-ray were used for stone scanning. After treatment, 63 of 113 patients were submitted to medical therapy to aid stone expulsion: nifedipine 30 mg/day for 14 days administered to 35 patients with upper-middle ureteral stones (group A1) and tamsulosin 0.4 mg/day for 14 days administered to 28 patients with stones located in the distal ureter (group A2). The remaining 50 patients were used as a control group (29 upper-middle ureteral stones-B1-and 21 lower ureteral stones-B2-), receiving only pain-relieving therapy. No significant difference in stone size between the groups defined was observed. Stone clearance was assessed 1 and 2 months after ESWL by means of KUB, ultrasound scan and/or excretory urography. A stone-free condition was defined as complete stone clearance or the presence of residual fragments smaller than 3 mm in diameter. The stone-free rates in the expulsive medical therapy group were 85.7 and 82.1% for the nifedipine (A1) and tamsulosin (A2) groups respectively; stone-free rates in the control groups were 51.7 and 57.1% (B1 and B2, respectively). Five patients (14.3%) in group A1, 5 (17.8%) in group A2, 14 (48.3%) in group B1 and 9 (42.8%) in group B2 were not stone-free after a single ESWL session and required ESWL re-treatment or an endoscopic treatment. Medical therapy following ESWL to facilitate ureteral stone expulsion results in increased 1- and 2-month stone-free rates and in a lower percentage of those needing re-treatment. The efficacy of nifedipine for the upper-mid ureteral tract associated with ketoprofene makes expulsive medical therapy suitable for improving overall outcomes of ESWL treatment for ureteral stones.

Cross-over study of the influence of bicarbonate-rich mineral water on urinary composition in comparison with sodium potassium citrate in healthy male subjects

Urine volume is the greatest risk factor for nephrolithiasis. High fluid intake is the first general advice given to stone-forming patients for the prevention of their recurrence. The aim of the present study was to evaluate the influence of bicarbonate-rich mineral water (1715 mg bicarbonate/l) on urinary-stone risk factors in comparison with sodium potassium citrate, a well-established treatment for urinary stones. The mineral water and sodium potassium citrate were administered in equimolar concentrations, with respect to the alkali load. All investigations were carried out in healthy male subjects aged 23–38 years. The study followed a cross-over design. All subjects received a standardized diet during the cross-over phase, which was formulated according to the dietary recommendations of the German Society of Nutrition (). On the loading day of the cross-over phase, fruit tea was substituted for either mineral water or sodium potassium citrate dissolved in fruit tea. The treatment offered during the second part of the cross-over phase was continued for a 4-week follow-up under normal dietary conditions. During the cross-over phase, there was a significant increase in urinary pH (P<0·001). There was also a significant increase in the excretion of citric acid (P<0·01), a decrease in the excretion of oxalic acid, and therefore a decrease in the relative supersaturations for calcium oxalate and uric acid. In the follow-up phase also, the relative supersaturations decreased and there were beneficial effects on the other urinary variables. The effect of the bicarbonate-rich mineral water was similar to that of the sodium potassium citrate, which suggests that it could be useful in the prevention of the recurrence of calcium oxalate and uric acid stones.

Clinical study on the effect of mineral waters containing bicarbonate on the risk of urinary stone formation in patients with multiple episodes of CaOx-urolithiasis

Investigations in healthy persons have shown that drinking mineral water containing HCO(3) has a positive effect on urine supersaturated with calcium oxalate (SS(CaOx)). The present study evaluates in a common setting whether these effects are also relevant in patients with multiepisodic urinary stone formation. A total of 34 patients with evident multiepisodic CaOx-urolithiasis were included in the study. Patients with hyperparathyroidism, renal tubular acidosis, Wilson's disease, Cushing disease, osteoporosis and malignant diseases were excluded. In a cross-over design and double-blinded the patients received 1.5 l of a mineral water with 2.673 mg HCO(3)/l (test water) or the same amount of water with a low mineral content (98 mg HCO(3)/l) (control water) daily for 3 days. During the study period the patients diet was recorded in a protocol, but not standardised. The main target parameter was SS(CaOx )in 24 h urine. In addition, urinary pH and the most important inhibiting and promoting factors were measured in 24 h urine (Ca, Ox, Mg, Cit). Both waters tested led to a highly significant increase in 24 h urine volume without a difference between each other. In the group, drinking the water containing HCO(3) the urinary pH increased significantly and was within a range relevant for metaphylaxis of calcium oxalate stone formation (x=6.73). This change was highly significant compared to the control group. In addition, significantly increased magnesium and citrate concentration were also observed. Supersaturation with calcium oxalate decreased significantly and to a relevant extent; however, there was no difference between the waters tested. As expected, the risk of uric acid precipitation also decreased significantly under bicarbonate water intake. However, an increase of the risk of calcium phosphate stone formation was observed. It is evident that both waters tested are able to lower significantly and to a relevant extent the risk of urinary stone formation in patients with multiepisodic CaOx-urolithiasis. In addition, the bicarbonate water increases the inhibitory factors citrate and magnesium due to its content of HCO(3) and Mg. Thus, it can be recommended for metaphylaxis of calcium oxalate and uric acid urinary stones.

Effect of potassium citrate therapy on stone recurrence and regrowth after extracorporeal shockwave lithotripsy in children

BACKGROUND AND PURPOSE

Stone disease in children may cause functional and morphologic changes in the urinary tract during longer-term follow-up. Prevention of stone recurrence will be possible only with careful metabolic evaluation and appropriate management. The possible preventive effects of potassium citrate therapy on true stone recurrence, as well as regrowth rates after shockwave lithotripsy (SWL), were evaluated in children treated for renal stones.

PATIENTS AND METHODS

Following assessment of the efficacy of SWL, 96 children (72 male, 53 female aged 4 to 14 years with a mean of 6.6 years) were evaluated for the effects of potassium citrate on residual fragments as well as true new stone formation during long-term follow-up. All children had calcium-containing stones with normal renal morphology and function without any urinary-tract infection. Depending on the outcome of treatment, patients with and without residual stones were allocated independently to Group I (N = 52) and Group II (N = 44), which were matched for sex and age. Group I was given oral potassium citrate 1 mEq/kg daily for 12 months; the remaining children served as controls. Follow-up ranged from 12 to 36.6 months, with a mean of 24.4 months. Follow-up results for at least a year with respect to the stone recurrence or stone growth rates were recorded in both groups.

RESULTS

Stone-free children undergoing no specific therapy had significant new stone formation compared with the group receiving potassium citrate on a regular basis (34.6% and 7.6%, respectively). Children with residual fragments receiving no specific preventive measure also showed significant new stone formation, along with enlargement of the fragments.

CONCLUSION

In addition to stone removal, treatment of pediatric urolithiasis requires a thorough metabolic evaluation. Depending on the abnormalities, each patient should be advised on adequate drinking to increase the urine volume in accordance with body size. Although children with hypocitraturia may well benefit from therapeutic agents that raise the urine citrate concentration, our results did clearly show that all children bearing residual fragments should be counseled on adequate fluid intake along potassium citrate treatment to prevent stone regrowth or formation during long-term follow-up.

The Evolution-Informed Optimal Dietary Potassium Intake of Human Beings Greatly Exceeds Current and Recommended Intakes

An organism best fits the environment described by its genes, an environment that prevailed during the time period (millions of years) when evolution naturally selected the genes of its ancestors-those who survived to pass on their genes. When an organism's current environment differs from its ancestral one, the environment's mismatch with the organism's genome may result in functional disadvantages for the organism. The genetically conditioned nutritional requirements of human beings established themselves over millions of years in which ancestral hominins, living as hunter-gatherers, ate a diet markedly different from that of agriculturally dependent contemporary human beings. In that context, we sought to quantify the ancestral-contemporary dietary difference with respect to the supply of one of the body's major mineral nutrients: potassium. In 159 retrojected Stone Age diets, human potassium intake averaged 400 +/- 125 mEq/d, which exceeds current and recommended intakes by more than a factor of 4. We accounted for the transition to the relatively potassium-poor modern diet by the fact that the modern diet has substantially replaced Stone Age amounts of potassium-rich plant foods (especially fruits, leafy greens, vegetable fruits, roots, and tubers), with energy-dense nutrient-poor foods (separated fats, oils, refined sugars, and refined grains), and with potassium-poor energy-rich plant foods (especially cereal grains) introduced by agriculture (circa 10,000 years ago). Given the fundamental physiologic importance of potassium, such a large magnitude of change in potassium intake invites the consideration in human beings of whether the quantitative values of potassium-influenced physiologic phenomena (eg, blood pressure, insulin and aldosterone secretion rates, and intracellular pH) currently viewed as normal, in fact disaccord with genetically conditioned norms. We discuss the potential implications of our findings in respect to human health and disease.

Comparative value of orange juice versus lemonade in reducing stone-forming risk

Foods that are high in citrate content generally are assumed to deliver alkali load when consumed irrespective of the accompanying cation. The object of this randomized, crossover study was to compare the effects of orange juice with those of lemonade on acid-base profile and urinary stone risks under controlled metabolic conditions. Thirteen volunteers (nine healthy subjects and four stone formers) sequentially received distilled water, orange juice, or lemonade while on constant metabolic diet. Twenty-four-hour urine samples were collected for acid-base parameters and stone risk analysis. Orange juice but not lemonade provided alkali as evidenced by higher net gastrointestinal alkali absorption and higher urinary pH and citrate compared with control. Urinary calcium was not significantly different, but urinary oxalate was higher during the orange juice phase. The calculated supersaturation of calcium oxalate was lower in the orange juice phase compared with control. Calculated undissociated uric acid was lower in the orange juice phase compared with both control and lemonade phases. The calculated supersaturation of brushite was significantly higher in the orange juice phase compared with both control and lemonade phases. Despite comparable citrate content, this study showed that orange juice has greater alkalinizing and citraturic effects than lemonade. Consumption of orange juice was associated with lower calculated calcium oxalate supersaturation and lower calculated undissociated uric acid. This short-term study suggests that orange juice consumption could result in biochemical modification of stone risk factors; however, additional studies are needed to evaluate its role in long-term prevention of recurrent nephrolithiasis.

Prophylactic and therapeutic properties of a sodium citrate preparation in the management of calcium oxalate urolithiasis: randomized, placebo-controlled trial

The purpose of this study was to investigate the prophylactic and therapeutic effects of a hitherto untested preparation containing sodium citrate in the management of calcium oxalate urolithiasis. In this study, a host of calcium oxalate kidney stone risk factors was investigated using a randomised, placebo controlled, "within-patient" clinical trial. The trial involved four groups of subjects: healthy male controls, healthy female controls , calcium oxalate stone-forming males and calcium oxalate stone-forming females. There were 30 subjects in each group. Twenty subjects in each group ingested the preparation containing sodium citrate and ten subjects in each group ingested a placebo for 7 days. Collection of 24 h urines were carried out at baseline, at day 7 and day 10 (i.e. 3 days after suspension of drug/placebo ingestion). These were analysed for biochemical and physicochemical risk factors. They were also tested for their inhibitory properties in crystallization experiments. Data were statistically analyzed using analysis of variance (ANOVA). Key risk factors were significantly and beneficially altered across all groups after ingestion of the preparation. The pH and urinary citrate excretion increased while urinary oxalate and calcium excretions decreased, as did relative supersaturations of calcium oxalate and uric acid. In addition, inhibition of calcium oxalate crystallization increased. Beneficial carryover effects were observed for some risk factors. The results of this study have demonstrated, for the first time, that a sodium citrate-containing preparation favourably alters the risk factors for calcium oxalate urolithiasis.

The effect of fruits and vegetables on urinary stone risk factors

BACKGROUND

The overall effect of fruit and vegetable intake on urinary stone risk profile is not yet known.

METHODS

We studied the effect of a two-week period of fruit and vegetable elimination on urinary stone risk profile in 12 normal adults, and of supplementing the diet with a fair quantity of low-oxalate fruits and vegetables in 26 idiopathic calcium stone formers characterized by hypocitraturia and a very low fruit and vegetable intake in their usual diet.

RESULTS

In the normal subjects, the elimination of fruits and vegetables from the diet decreased the urinary excretion of potassium (-62%), magnesium (-26%), citrate (-44%) and oxalate (-31%), and increased that of calcium (+49%) and ammonium (+12%) (P < 0.05 for all). The relative saturation for calcium oxalate and calcium phosphate increased from 6.33 to 8.24 (P = 0.028), and from 0.68 to 1.58 (P = 0.050), respectively. In the hypocitraturic stone formers, the introduction of these foods in the diet increased urinary volume (+64%), pH (from 5.84 to 6.19), excretion of potassium (+68%), magnesium (+23%), and citrate (+68%), while it decreased the excretion of ammonium (-18%) (P < 0.05 for all). The relative saturation for calcium oxalate and uric acid fell from 10.17 to 4.96 (P < 0.001), and from 2.78 to 1.12 (P = 0.003), respectively.

CONCLUSION

The total elimination of fruits and vegetables in normal subjects brings about adverse changes in the urinary stone risk profile that are only partially counterbalanced by a reduction in oxalate. In contrast, the addition of these foods to the diet of hypocitraturic stone formers not used to eating them not only significantly increases citrate excretion without affecting oxalate excretion, but also decreases calcium oxalate and uric acid relative saturation.

Citrate and Urolithiasis

Kidney stones are an endemic pathology in mediterranean area. Although urologists have developed a lot of mini-invasive techniques to treat this pathology they usually do not have background to treat the medical aspect of lithiasis. For this reason we underline the necessity to know the lithogenetic mechanism starting from the formation of a simple salt like Ca – Ox and is growing as macrocrysthal. In this work we describe the etiology stone formation, metabolic evaluation and medical treatment of urinary stones. Underlining the role of citrate as a inhibitor of crystallogenesis and his role in medical chemiolisis.

Mechanism of acid-induced bone resorption

PURPOSE OF REVIEW

This review presents our current understanding of the way metabolic acidosis induces calcium efflux from bone, and in the process, buffers additional systemic hydrogen ions associated with acidosis.

RECENT FINDINGS

Acid-induced changes in bone mineral are consistent with a role for bone as a proton buffer. In response to metabolic acidosis in an in-vitro bone organ culture system, we observed a fall in mineral sodium, potassium, carbonate and phosphate, which each buffer protons and in vivo should increase systemic pH towards the physiologic normal. Initially, metabolic acidosis stimulates physicochemical mineral dissolution and subsequently cell-mediated bone resorption. Acidosis suppresses the activity of bone-resorbing cells, osteoblasts, decreasing gene expression of specific matrix proteins and alkaline phosphatase activity. There is concomitant acid stimulation of prostaglandin production by osteoblasts, which acting in a paracrine manner increases synthesis of the osteoblastic receptor activator of nuclear factor kappa B ligand (RANKL). The acid induction of RANKL then stimulates osteoclastic activity and recruitment of new osteoclasts to promote bone resorption and buffering of the proton load. Both the regulation of RANKL and acid-induced calcium efflux from bone are mediated by prostaglandins.

SUMMARY

Metabolic acidosis, which occurs during renal failure, renal insufficiency or renal tubular acidosis, results in decreased systemic pH and is associated with an increase in urine calcium excretion. The apparent protective function of bone to help maintain systemic pH, which has a clear survival advantage for mammals, will come partly at the expense of its mineral stores.

The metabolic syndrome and uric acid nephrolithiasis: novel features of renal manifestation of insulin resistance

BACKGROUND

Uric acid nephrolithiasis primarily results from low urinary pH, which increases the concentration of the insoluble undissociated uric acid, causing formation of both uric acid and mixed uric acid/calcium oxalate stones. These patients have recently been described as exhibiting features of insulin resistance. This study was designed to evaluate if insulin resistance is associated with excessively low urinary pH in overtly healthy volunteers (non-stone formers) and if insulin resistance may explain the excessively low urinary pH in patients with uric acid nephrolithiasis.

METHODS

Fifty-five healthy volunteers (non stone-formers) with a large range of body mass index and 13 patients with recurrent uric acid nephrolithiasis underwent hyperinsulinemic euglycemic clamp, 24-hour urinary studies, and anthropometric measurements of adiposity. A subgroup of 35 non-stone formers had 2-hour timed urinary collection before and during the hyperinsulinemic phase of the clamp studies.

RESULTS

For the non-stone former population, low insulin sensitivity measured as glucose disposal rate significantly correlated with low 24-hour urinary pH (r= 0. 35; P= 0.01). In addition to the previously described acidic urine pH and hypouricosuria, patients with recurrent uric acid nephrolithiasis were found to be severely insulin resistant (glucose disposal rate: uric acid stone-formers vs. normals; 4.1 +/- 1.3 vs. 6.9 +/- 2.1 mg/min/kg of lean body mass, P= 0.008). Acute hyperinsulinemia was associated with higher urinary pH (6.1 +/- 0.7 at baseline to 6.8 +/- 0.7 during hyperinsulinemia; P < 0.0001), urinary ammonia excretion (2.7 +/- 1.6 mEq/2 hr at baseline and 4.0 +/- 2.6 mEq/2 hr P= 0.002) and urinary citrate excretion (48 +/- 33 mg/2 hr at baseline and 113 +/- 68 mg/2 hr P < 0.0001).

CONCLUSION

We conclude that one renal manifestation of insulin resistance may be low urinary ammonium and pH. This defect can result in increased risk of uric acid precipitation despite normouricosuria.

Effect of high protein diet on stone-forming propensity and bone loss in rats

BACKGROUND

High protein diets are believed to cause kidney stone formation and bone loss, but the mechanisms mediating these changes are unknown. The purpose of this study was to create an animal model of animal protein excess and to evaluate the response of kidney and bone to the dietary protein load.

METHODS

Rats (12 per group) were pair-fed with a high (48%) and low (12%) casein diets that were otherwise identical in their content of sodium, potassium, calcium, phosphorus, and magnesium.

RESULTS

Compared with the low casein group, the high casein group delivered a substantial acid load during 59 days of study, since it significantly decreased urinary pH, and increased urinary ammonium, titratable acidity, and net acid excretion. Animals on high casein diet also had higher urinary volumes. On the high casein diet, urinary calcium excretion was significantly higher and urinary citrate excretion and concentration was significantly lower. On the high casein diet, urinary saturation of calcium phosphate was higher. Serum calcitriol concentration did not significantly differ between the two groups. Histomorphometric analysis of femur procured after 59 days on the diet showed marked increase in bone resorption in the high casein group. Hypocitraturia was associated with increased activity of sodium-citrate cotransporter in renal cortical brush-border membranes (BBM) in the high casein group.

CONCLUSION

Both the kidney and bone contribute to the pathogenesis of hypercalciuria during high casein diet in rats. Hypocitraturia is probably renal in origin. This rat model will be useful in elucidating the mechanisms by which high protein intake increases the risk of nephrolithiasis and bone loss in human beings.

Idiopathic calcium oxalate urolithiasis: risk factors and conservative treatment

Idiopathic calcium oxalate urolithiasis is a frequent and recurrent multifactorial disease. This review focuses on urinary and dietary risk factors for this disease and conservative strategies for rectifying them. Dietary oxalate and calcium and their respective urinary excretions have been extensively investigated during the last 10 years. Urinary oxalate has emerged as the most important determinant of calcium oxalate crystallization while the role of urinary calcium has shifted to bone balance and osteoporosis. Dietary calcium restriction increases urinary oxalate and contributes to a negative bone balance. It has therefore been abandoned as a means to reduce the risk of calcium oxalate kidney stone formation. Calcium oxalate kidney stone patients are advised to increase their fluid intake to achieve a urine volume of 2 l or more; the recommended calcium intake is 800-1200 mg/day; high oxalate foods should be restricted; daily protein intake should be between 0.8 and 1 g/kg body weight/day; essential fats should be included; vegetable and fruit (except oxalate-rich vegetables) intake should be increased. The use of calcium supplements has potential benefits but needs to be examined further.

Effects of potassium citrate supplementation on bone metabolism

Western diets rich in animal protein result in long-term acid loading that, despite corresponding increases in net renal acid excretion, may induce a chronic state of acidemia. This may have deleterious effects on both the kidney and bone, by increasing the risk of calcium stone in the former and leading to chemical dissolution of mineral alkaline salts in the latter. Whereas supplementation with alkaline citrate has been shown to reduce stone recurrences, its effect on bone turnover has received less attention. The aim of the present study was to evaluate whether potassium citrate favorably affects bone turnover markers in postmenopausal females with low bone density. Thirty women, aged 58 +/- 8.1 years, were enrolled and studied on basal conditions and after a 3-month course of potassium citrate supplementation (0.08-0.1 g/kg b.w. daily). Twenty-two women concluded the study while 8 withdrew. Twenty-four age-matched healthy women were taken as control cases. All were evaluated for electrolyte and acid-base balance-related parameters, bone turnover, markers and renal function. A significant decrease in net acid excretion was observed upon citrate supplementation, and this was paralleled by a significant decrease of urinary deoxypyridinolines, hydroxyproline-to-creatinine ratios, and, to a lesser extent, serum osteocalcin. Percent variations of urine citrate were inversely related to those of deoxypyridinolines and hydroxyproline. No change in these chemistries occurred in the control group. Our results suggest that treatment with an alkaline salt, such as potassium citrate, can reduce bone resorption thereby contrasting the potential adverse effects caused by chronic acidemia of protein-rich diets.

Mechanism and Molecular Determinant for Regulation of Rabbit Transient Receptor Potential Type 5 (TRPV5) Channel by Extracellular pH

The transient receptor potential type 5 (TRPV5) channel is present in kidney and intestine and important for transepithelial (re)absorption of calcium in these tissues. We report that in whole-cell patch clamp recording extracellular acidification inhibited rabbit TRPV5 with apparent pKa approximately 6.55. The two extracellular loops between the fifth and sixth transmembrane segments of TRPV5 presumably form part of the outer opening of the pore and likely are important in binding and regulation by external protons. We found that mutation of glutamate 522 to glutamine (E522Q) decreased the sensitivity of the channel to extracellular acidification. Mutations of other titratable amino acids within the two extracellular loops to non-titratable amino acids had no effect on pH sensitivity. Substitutions of aspartate or other titratable amino acids for glutamate 522 conferred an increase in pH sensitivity. The pH sensitivity mediated by glutamate 522 was independent of extracellular or intracellular Mg2+. Single channel analysis revealed that extracellular acidification reduced single channel conductance as well as open probability of the wild type channel. In contrast to wild type channel, extracellular acidification did not reduce open probability for E522Q mutant. Methanethiosulfonate reagents inhibited the activity of glutamine 522 to cysteine mutant channel with a reaction rate constant approaching that with free thiols in solution, suggesting that glutamate 522 is located on the surface of the channel. These data suggest that glutamate 522 of the rabbit TRPV5 is a "pH sensor," and extracellular protons inhibit TRPV5 likely by altering conformation of the channel protein.

Chronic metabolic acid load induced by changes in dietary electrolyte balance increased chloride retention but did not compromise bone in growing swine

The effects of chronic dietary acid loads on shifts in bone mineral reserves and physiological concentrations of cations and anions in extracellular fluids were assessed in growing swine. Four trials were conducted with a total of 38 (8.16 +/- 0.30 kg, mean +/- SEM) Large White x Landrace x Duroc pigs randomly assigned to one of three dietary treatments. Semipurified diets, fed for 13 to 17 d, provided an analyzed dietary electrolyte balance (dEB, meq/kg diet = Na+ + K+ - Cl-) of -35, 112, and 212 for the acidogenic, control, and alkalinogenic diets, respectively. Growth performance, arterial blood gas, serum chemistry, urine pH, mineral balance, bone mineral content gain, bone-breaking strength, bone ash, and percentage of bone ash were determined. Dietary treatments created a range of metabolic acid loads without affecting (P > 0.10) growth or feed intake. Urine pH was 5.71, 6.02, and 7.65 +/- 0.48 (mean +/- SEM) and arterial blood pH was 7.478, 7.485, and 7.526 +/- 0.006 for pigs fed acidogenic, control, and alkalinogenic treatments, respectively. A lower dEB resulted in an increased (P < 0.001) apparent Cl- retention (106.6, 55.4, and 41.2 +/- 6.3 meq/d), of which only 1.6% was accounted for by expansion of the extracellular fluid Cl- pool as calculated from serum Cl- (105.5, 103.4, 101.6 +/- 0.94 meq/L (mean +/- SEM) for pigs fed acidogenic, control, and alkalinogenic treatments, respectively. A lower dEB did not decrease (P > 0.10) bone mineral content gain, bone-breaking strength, bone ash, percentage of bone ash, or calcium and phosphate balance. In conclusion, bone mineral (phosphate) was not depleted to buffer the dietary acid load in growing pigs over a 3-wk period.

Effects of calcium carbonate, magnesium oxide and sodium citrate bicarbonate health supplements on the urinary risk factors for kidney stone formation

We describe a model to illustrate different chemical interactions that can occur in urine following ingestion of individual and combined health supplements. Two types of interactions are defined: synergism and addition. The model was applied to eight healthy males who participated in a study to investigate the chemical interactions between calcium carbonate, magnesium oxide and sodium citrate-bicarbonate health supplements on calcium oxalate urinary stone risk factors. Subjects ingested these components individually and in combination for 7 days. Twenty-four-hour urines were collected at baseline and during the final day of supplementation. These were analysed using standard laboratory techniques. Three different chemical interactions, all involving citrate, were identified: magnesium and citrate exerted a synergistic effect on lowering the relative superaturation (RS) of brushite; the same two components produced a synergistic effect on raising pH; finally, calcium and citrate exerted an additive effect on lowering the RS of uric acid. We propose that the novel approach described in this paper allows for the evaluation of individual, additive and synergistic interactions in the assessment of the efficacy of stone-risk reducing preparations.

Neutralization of Western diet inhibits bone resorption independently of K intake and reduces cortisol secretion in humans

A Western-type diet is associated with osteoporosis and calcium nephrolithiasis. On the basis of observations that calcium retention and inhibition of bone resorption result from alkali administration, it is assumed that the acid load inherent in this diet is responsible for increased bone resorption and calcium loss from bone. However, it is not known whether the dietary acid load acts directly or indirectly (i.e., via endocrine changes) on bone metabolism. It is also unclear whether alkali administration affects bone resorption/calcium balance directly or whether alkali-induced calcium retention is dependent on the cation (i.e., potassium) supplied with administered base. The effects of neutralization of dietary acid load (equimolar amounts of NaHCO(3) and KHCO(3) substituted for NaCl and KCl) in nine healthy subjects (6 men, 3 women) under metabolic balance conditions on calcium balance, bone markers, and endocrine systems relevant to bone [glucocorticoid secretion, IGF-1, parathyroid hormone (PTH)/1,25(OH)(2) vitamin D and thyroid hormones] were studied. Neutralization for 7 days induced a significant cumulative calcium retention (10.7 +/- 0.4 mmol) and significantly reduced the urinary excretion of deoxypyridinoline, pyridinoline, and n-telopeptide. Mean daily plasma cortisol decreased from 264 +/- 45 to 232 +/- 43 nmol/l (P = 0.032), and urinary excretion of tetrahydrocortisol (THF) decreased from 2,410 +/- 210 to 2,098 +/- 190 microg/24 h (P = 0.027). No significant effect was found on free IGF-1, PTH/1,25(OH)(2) vitamin D, or thyroid hormones. An acidogenic Western diet results in mild metabolic acidosis in association with a state of cortisol excess, altered divalent ion metabolism, and increased bone resorptive indices. Acidosis-induced increases in cortisol secretion and plasma concentration may play a role in mild acidosis-induced alterations in bone metabolism and possibly in osteoporosis associated with an acidogenic Western diet.

Medical evaluation of nephrolithiasis

A careful and individualized evaluation of risk factors is a fundamental part of the management of patients with urinary tract stone disease. Identification and correction of important abnormalities provide the basis for designing an efficient and rational treatment program, aiming at an arrest or at least reduction of recurrent stone formation. It is beyond doubt that appropriate therapeutic steps in this regard are of great benefit for the patient. It needs to be emphasized, however, that no success will be obtained unless the patient is willing and able to follow the ensuing dietary recommendations and medical advice.

Pathophysiology of hypocitraturic nephrolithiasis

Urinary citrate inhibits calcium stone formation by complexing calcium in a soluble form and by effects on urinary crystals to prevent growth to stones. Low urinary citrate has been recognized for several decades as a contributing factor in some stone forming patients, but recent studies have elucidated the mechanisms and derangements of the renal handling of citrate in various conditions. In addition, oral citrate as an alkalinizing agent can not only increase urinary citrate, but also favorably impact other stone-promoting conditions. This review will focus on the understanding of these concepts.