Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones.

Background: Urinary sulfate (SO4(2-)) and thiosulfate (S2O3(2-)) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts.

Methods: Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1).

Enteric hyperoxaluria secondary to small bowel resection: use of computer simulation to characterize urinary risk factors for stone formation and assess potential treatment protocols.

Background And Purpose: We used computer modeling to investigate the influence of physicochemical stone risk factors on urinary supersaturation (SS) of calcium oxalate (CaOx) in patients with severe hyperoxaluria, relative hypocalciuria, hypocitraturia, and CaOx nephrolithiasis after extensive small bowel resection, usually performed for Crohn's disease. We also simulated different treatment strategies, including oral calcium supplements and citrate, in such patients.

Materials And Methods: A baseline urine model was derived by consolidating data acquired by ourselves with those from another patient cohort.

Effects of vitamin E ingestion on plasma and urinary risk factors for calcium oxalate urolithiasis in two population groups having different stone-risk profiles: evidence of different physiological handling mechanisms.

It has been demonstrated that vitamin E supplementation reduces calciuria and oxaluria and that it may also prevent oxalate-mediated peroxidative injury, all of which reduce the risk of calcium oxalate urolithiasis. In view of the significant difference in stone occurrence in black (B) and white (W) South Africans, we undertook to investigate the effects of vitamin E supplementation in subjects from these two groups. Five healthy males from each group ingested one capsule (400 IU) of vitamin E daily for 60 days.

Simulating calcium salt precipitation in the nephron using chemical speciation.

Theoretical modeling of urinary crystallization processes affords opportunities to create and investigate scenarios which would be extremely difficult or impossible to achieve in in vivo experiments. Researchers have previously hypothesized that calcium renal stone formation commences in the nephron. In the present study, concentrations of urinary components and pH ranges in different regions of the nephron were estimated from concentrations in blood combined with a knowledge of the renal handling of individual ions.

Risk factors for renal calcium stone formation in South African and European young adults.

Objectives: The different susceptibility to renal stone disease of white and black people has been previously explained in terms of intrinsic (genetics) and extrinsic (diet, lifestyle) factors. However, in South Africa, the absence of stone disease in the black population has not yet been fully explained by either of these. The aim of the present study was to identify potential differences between black and white subjects in South Africa and white subjects in Europe with respect to their relative dietary and urinary risk factors for renal stone formation.

Evening primrose oil supplementation increases citraturia and decreases other urinary risk factors for calcium oxalate urolithiasis.

Purpose: We investigated the effects of gamma-linolenic acid (an omega-6 polyunsaturated fatty acid) in the form of evening primrose oil on calcium oxalate urinary stone risk factors in 2 ethnic groups.

Materials And Methods: Eight black and 8 white healthy male subjects ingested 1,000 mg evening primrose oil (Natrodale, Kuils River, South Africa) daily for 20 days while following a free diet. Arachidonic acid content was determined by a dietary questionnaire.

Calcium oxalate stone formation risk - a case of disturbed relative concentrations of urinary components.

Background: Although afflicted with stone formation, urolithiasis patients often present with normal renal excretions of lithogenic and inhibitory substances. In this study, crystal formation is not interpreted as the result of urinary excretions simply exceeding the static limits of normal ranges but rather as the consequence of relative combinations of such parameters which convert urine into becoming potentially lithogenic. Our model embraces different triplet combinations of fundamental urinary risk factors for calcium oxalate (CaOx) crystallization, to characterize different levels of urinary stone formation risk.

Therapeutic action of citrate in urolithiasis explained by chemical speciation: increase in pH is the determinant factor.

Background: The therapeutic action of citrate in the management of calcium oxalate urolithiasis has been attributed to the depletion of free calcium ions by complexation of the latter by citrate itself. However, little attention has been given to the nature of such complexes and the chemical conditions which control their formation because it is very difficult to measure them in solution. We therefore modelled the theoretical formation of these complexes in urine following administration of a citrate-containing preparation, using a powerful speciation program, JESS (Joint Expert Speciation System), which has been widely used to model metal-ligand equilibria in biological systems but which has hitherto not been applied in urolithiasis research.

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.