Rice-bran treatment for calcium stone formers with idiopathic hypercalciuria

Increased Water Viscosity Enhances Water Intake and Reduces Risk of Calcium Oxalate Stone Formation in Cats

The purpose of this study is to determine if water with increased viscosity results in increased water intake, thus lowering the risk of urolithiasis in cats. Twelve healthy adult cats were fed pre-trial standard dry maintenance food for 1 week and then randomized into two groups for the study phase. The cats continued to receive the same food but were provided either control (deionized) water or viscous (1% methylcellulose) water for two months and then switched to the other water type for two months in a cross-over study design with repeated measures. Complete blood counts, serum chemistry profiles, and urinalysis were performed at the initiation of the study and again at 1, 2, 3, and 4 months. Daily water consumption and energy intake for each cat were recorded. Body weights were assessed weekly. Cats consuming 1% methylcellulose water with increased viscosity had increased water intake (p < 0.001; 25% and 21% higher at 28 and 56 days, respectively). Increased consumption of water resulted in lower urine specific gravity (p = 0.04), serum creatinine (p = 0.02), and blood urea nitrogen (p = 0.002) concentrations (without changing serum albumin, glucose, and calcium concentrations or serum osmolality) and decreased urine calcium concentration (p = 0.01) compared with cats consuming control water. In addition, the increased water intake increased (p = 0.05) resistance to oxalate crystal formation.

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.

Influence of a low- and a high-oxalate vegetarian diet on intestinal oxalate absorption and urinary excretion

OBJECTIVE

To compare quantitatively the effect of a low- and a high-oxalate vegetarian diet on intestinal oxalate absorption and urinary excretion.

SUBJECTS AND METHODS

Eight healthy volunteers (three men and five women, mean age 28.6+/-6.3) were studied. Each volunteer performed the [(13)C(2)]oxalate absorption test thrice on a low-oxalate mixed diet, thrice on a low-oxalate vegetarian diet and thrice on a high-oxalate vegetarian diet. For each test, the volunteers had to adhere to an identical diet and collect their 24-h urines. In the morning of the second day, a capsule containing [(13)C(2)]oxalate was ingested.

RESULTS

On the low-oxalate vegetarian diet, mean intestinal oxalate absorption and urinary oxalate excretion increased significantly to 15.8+/-2.9% (P=0.012) and 0.414+/-0.126 mmol/day (P=0.012), compared to the mixed diet. On the high-oxalate vegetarian diet, oxalate absorption (12.5+/-4.6%, P=0.161) and urinary excretion (0.340+/-0.077 mmol/day, P=0.093) did not change significantly, compared to the mixed diet.

CONCLUSIONS

A vegetarian diet can only be recommended for calcium oxalate stone patients, if the diet (1) contains the recommended amounts of divalent cations such as calcium and its timing of ingestion to a meal rich in oxalate is considered and (2) excludes foodstuffs with a high content of nutritional factors, such as phytic acid, which are able to chelate calcium.

Intestinal transport of an obdurate anion: oxalate

In this review, we focus on the role of gastrointestinal transport of oxalate primarily from a contemporary physiological standpoint with an emphasis on those aspects that we believe may be most important in efforts to mitigate the untoward effects of oxalate. Included in this review is a general discussion of intestinal solute transport as it relates to oxalate, considering cellular and paracellular avenues, the transport mechanisms, and the molecular identities of oxalate transporters. In addition, we review the role of the intestine in oxalate disease states and various factors affecting oxalate absorption.

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 magnesium citrate and phytin on reducing urinary calcium excretion in rats

The aim of this study was to determine and compare the effects of both magnesium citrate and phytin on reducing urinary calcium excretion under high-calcium-diet conditions during single and combined treatments. An animal experiment was carried out over a period of 4 weeks in 35 male rats. Urinary calcium excretion was reduced significantly by magnesium citrate and/or phytin in rats fed on high-calcium diets. The hypocalciuric effect of magnesium citrate was more evident than that of phytin. Urinary magnesium excretion was high in all experimental groups. However, the urinary magnesium/calcium ratios showed a consistent increase only in the groups treated with magnesium citrate. Urinary citrate excretion showed a relative increase with the introduction of magnesium citrate plus phytin; however, in both the high-calcium-diet group and the magnesium-citrate group this was found to be reduced. Urinary phosphate excretion was slightly higher in the groups treated with phytin. There was no definite difference in urinary oxalate concentration between the groups. No significant change was noted in the serum concentration of calcium, magnesium, or phosphate.

Results of long-term rice bran treatment on stone recurrence in hypercalciuric patients

A series of 182 calcium stone formers with idiopathic hypercalciuria underwent treatment with rice bran for 1 to 94 months. Urinary calcium excretion was considerably reduced, but there was some increase in urinary phosphate and oxalate. Urinary excretion of magnesium and uric acid, serum calcium, magnesium, phosphate, uric acid, parathyroid hormone (PTH) and ALP was unaffected. There were no obvious changes in serum iron, zinc and copper even when patients were treated for long periods. Rice bran was well tolerated in almost all cases and there were no serious side effects; 49 patients have undergone treatment for more than 3 years (average duration of administration 5.09 years). The frequency of new stone formation was drastically reduced (individual stone formation rate (no./year) from 0.720 +/- 0.533 to 0.125 +/- 0.204; group stone formation rate (no./patient-year) from 0.721 to 0.120) compared with the 3-year period before treatment. During treatment, 61.2% of patients remained in remission. Although rice bran therapy should be effective in correcting absorptive hypercalciuria, there may be limits to the overall ability of rice bran monotherapy to prevent recurrence.

Prophylaxis in idiopathic calcium urolithiasis

The most important measure in the prophylaxis of idiopathic calcium urolithiasis is dietary advice. Patients should be kept to a high-fluid intake, increasing their diuresis by at least 0.51. The mineral content of drinking water seems to be of minor importance, but the liquid should be low in carbohydrates and oxalate. The intake of animal proteins should be reduced to no more than five meals with meat, fish or poultry per week. Excesses of oxalate-rich food must be avoided. The daily intake of calcium in dairy products should be in the range of 800-1200 mg. Sodium and refined carbohydrates should be moderately restricted. Medical treatment is indicated only in cases of recurrence under the appropriate diet. Selective treatment according to urinary chemical composition is favoured; alkali citrate, thiazides, allopurinol, and pyridoxine are of major interest.

Effect of unprocessed wheat bran on calciuria and oxaluria in patients with urolithiasis

Seventeen hypercalciuria patients (8 control, 9 treatment) with a history of urolithiasis were randomly selected to receive low-calcium, low-oxalate diets with or without the addition of 30 g of dietary fiber as unprocessed wheat bran. Diet alone resulted in a 5.6 percent decrease in calciuria compared with a 23.5 percent decrease with the addition of the fiber. The addition of hydrochlorothiazide and potassium citrate further reduced calciuria by 40.4 percent and 34.5 percent, respectively. Oxaluria was decreased 21.4 percent by diet alone compared with 3.9 percent in the diet and fiber treatment group. Patient compliance to diets was good, and no complications resulted from fiber intake.