Dietary factors in the pathogenesis and prophylaxis of calcium nephrolithiasis

Changes in urinary magnesium, citrate, and oxalate levels due to cola consumption

The serum concentration and urinary excretion of four potential stone constituents: calcium, oxalate, phosphate, and uric acid; and of two potential inhibitors of urinary stone formation, citrate and magnesium, were studied before and during ingestion of a carbonated cola beverage. Four participants, after baseline serum determinations, abstained for forty-eight hours from cola consumption and then attempted to drink 3 quarts per day of cola in the following forty-eight hours. One participant failed to drink more than two quarts per day of cola. In all 4 participants twenty-four-hour urinary excretion of magnesium decreased by an average of 2.6 mg. In the 3 participants who succeeded in drinking 3 quarts of cola per day, twenty-four-hour urinary excretion of oxalate increased an average of 8.3 mg and excretion of citrate decreased an average of 122 mg. These results demonstrate changes in urine constituents which could contribute to enhanced kidney stone formation in patients who drink large quantities of cola-flavored carbonated beverages.

Environmental factors in the pathophysiology of recurrent idiopathic calcium urolithiasis (RCU), with emphasis on nutrition

A number of environmental factors are under discussion as possibly implicated in the etiology of RCU. On the basis of data in the literature and our own results, we attempted a critical weighting up of the possible contributions of climate, pollution, stress, nutrition in general and especially oxalate and minerals in the nutrition. It was concluded that there is a need for more in-depth research into the response of the body to challenges from the environment, in particular nutrition.

Stone-forming potential of milk or calcium-fortified orange juice in idiopathic hypercalciuric adults

Milk and orange juice (OJ) fortified with calcium-citrate-malate (CCM; calcium-citrate-malate salt is a coined term to describe a trademarked calcium delivery system found only in Citrus Hill Plus Calcium) were evaluated for their potential to alter urine chemistries and crystallization during the course of an eleven week, crossover study. Six male and six female, non-stone-forming, idiopathic hypercalciuric adults consumed 600 mg per day as beverage calcium for four consecutive weeks. The results show that both milk and CCM-fortified OJ (CCM-OJ) were well tolerated by male and female hypercalciurics since few significant changes occurred in overall urinary chemistry profiles. CCM-OJ did, however, significantly (P less than or equal to 0.05) increase urinary pH relative to milk in both sexes and urinary citrate concentration in women only. Both of these urinary parameters were significantly increased by CCM-OJ in both sexes relative to the basal period. The combined pH and citrate effects are recognized to protect against calcium oxalate stone formation through formation of the soluble calcium citrate salt. These data indicate that either milk or CCM-fortified orange juice can be consumed, at least within the limits tested, as a dietary source of calcium without increasing the risk of stone formation in a calcium-sensitive subpopulation. That the urine chemistries and crystallization of such calcium-sensitive individuals does not significantly change with the consumption of either beverage implies that the urine of normal individuals would be exceedingly unlikely to change as well.

Diet, vitamin D and vertebral mineral density in hypercalciuric calcium stone formers

To elucidate the pathophysiology of dietary calcium independent hypercalciuria, 42 calcium stone formers (Ca SF) were selected because they had on free diet a calciuria greater than 0.1 mmol/kg/day. For four days they were put on a diet restricted in calcium (Ca RD) by exclusion of the dairy products. They collected 24 hour urines on free diet and on day 4 of Ca RD as well as the two-hour fasting urines on the morning of the day 5 and the four-hour urines passed after an oral calcium load of 1 g, for measurement of creatinine, Ca, PO4, urea and total hydroxyprolinuria (THP). On day 5 fasting plasma concentrations of Ca, PO4, intact PTH, Gla protein, calcidiol and calcitriol were measured. The patients were firstly classified into dietary hypercalciuria (DH, 18 patients) and dietary calcium-independent hypercalciuria (IH, 24 patients) on the basis of the disappearance or not of hypercalciuria on Ca RD. Then the patients with IH were subclassified into absorptive hypercalciuria (AH) because of normal fasting calciuria (8 patients) and into fasting hypercalciuria (16 patients). Fasting hypercalciuric patients were subsequently divided according to the PTH levels into renal hypercalciuria (RH, 1 patient) with elevated fasting PTH becoming normal after the Ca load and undetermined hypercalciuria (UH, 15 patients) with normal PTH levels. Furthermore, their vertebral mineral density (VMD) was measured by quantitative computerized tomography which was normal in DH (91 +/- 6% of the normal mean for age and sex) but was decreased in IH to 69 +/- 4%. No difference in VMD was observed between AH and UH. Urinary excretions of urea, phosphate and THP was higher in IH than in DH and comparable in AH and UH. Sodium excretion Ca RD was the same in all groups and subgroups as well as the plasma parameters. Plasma calcitriol was increased in IH and DH comparatively to normal in spite of normal plasma calcidiol. Calciuria increase after oral calcium load, an index of Ca absorption, was higher in IH than in controls and comparable in IH and DH as well as in the three subgroups of IH. From these data and correlation studies in IH it is concluded: (1.) VMD is decreased in Ca stone formers with IH but not in those with DH, making the distinction of these two groups of hypercalciuria patients clinically relevant.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypercalciuria and stones

Hypercalciuria, defined as the urinary excretion of more than 0.1 mmol Ca/kg/d (4 mg/kg/24 h), is observed in approximately 50% of patients with calcium oxalate/apatite nephrolithiasis and is one of the risk factors for stone formation. Urinary Ca excretion rates among such patients are higher than normal, despite comparable ranges of glomerular filtration rate (GFR) and serum ultrafiltrable Ca concentrations, and thus glomerular filtration of Ca, suggesting that hypercalciuria is the result of inhibition of net tubular Ca reabsorption. Although increased dietary NaCl or protein intake and reduced K intake increase urinary Ca excretion rates, urinary Ca excretion rates are higher among hypercalciuric stone formers than among normal subjects in relation to comparable ranges of urinary Na, SO4 (as a reflection of protein intake), or K excretion rates, indicating that these dietary factors are not primarily responsible for hypercalciuria. Hypophosphatemia is observed among a subset of hypercalciuric patients and consequent activation of 1,25-(OH)2-D synthesis increases intestinal Ca absorption and urinary calcium excretion. Other hypercalciuric patients exhibit augmented intestinal Ca absorption without elevated plasma 1,25-(OH)-2-D levels, suggesting that either the capacity of 1,25-(OH)2-D to upregulate its own receptor in the intestine or 1,25-(OH)2-D-independent intestinal Ca transport are responsible for increased Ca absorption and hypercalciuria. Hypercalciuric patients also exhibit accelerated radiocalcium turnover, negative Ca balances, reduced bone density, delayed bone mineralization, fasting hypercalciuria, and increased hydroxyproline excretion, all of which reflect participation of the skeleton and presumably a more generalized acceleration of Ca transport. Hypercalciuria may be familial.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of diet on urinary risk factors for stones in healthy subjects and idiopathic renal calcium stone formers

The daily intake of 103 recurrent idiopathic calcium stone formers and 146 controls was assessed by means of a computer-assisted 24-h dietary record. Timed 24-h urine samples were collected over the same period to assess the relationship between dietary intake of nutrients and urinary risk factors for calcium stones. After standardisation for sex, age and social status a total of 128 subjects underwent final statistical analysis; 64 renal stone formers and 64 controls. Significant increases in the consumption of animal and vegetable protein and purine were identified as the nutritional factors that distinguished renal stone formers from controls. As expected, the daily urinary excretion of calcium and oxalate was higher and the daily urinary excretion of citrate was lower in stone formers than in controls. No difference with respect to daily urinary uric acid excretion was recorded. Daily urinary excretion of calcium was correlated to dietary protein intake while daily urinary oxalate was correlated to dietary vitamin C intake. It was concluded that renal stone formers could be predisposed to stones because of their dietary patterns. A link between the protein content of the diet and urinary calcium was confirmed, but dietary animal protein had a minimal effect on oxalate excretion.

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.

Urolithiasis in children: current medical management

The mechanism of stone formation in the urinary tract is reviewed. Diet, urinary tract infection and metabolic disorders account for the different epidemiological patterns of stone formation. The diagnosis and management of renal tract calculi are discussed. Calcium stones are associated with hypercalciuria, urine acidification defects, the use of furosemide in premature babies, hypercalcaemia, hyperoxaluria, hyperuricosuria, an alkaline urine and hypocitraturia. Uric acid stones occur in acid urine, from increased purine synthesis with lympho- or myeloproliferative disorders or from several inborn errors of purine metabolism which can also cause xanthine or dihydroxyadenine stones. Cystinuria, inherited as an autosomal recessive disorder is best treated with a low sodium diet, a fluid intake exceeding 40 ml/kg per day maintaining urine pH between 7.5 and 8 and, if necessary, with oral penicillamine. Oxalate stones occur in relation to diet, bowel disease and primary inherited defects in oxalate metabolism. Urinary tract infection causing struvite and carbonate apatite formation is the commonest cause of stones in Europe.