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PubMed1997

Correspondence between stone composition and urine supersaturation in nephrolithiasis.

Supersaturation (SS) with respect to calcium oxalate monohydrate (COM), brushite (Br) and uric acid (UA), obtained in three 24-hour pretreatment urine samples from patients with stone disease were compared to the mineral composition of stones passed by the same patients to determine whether sparse urine SS measurements accurately reflect the long-term average SS values in the kidney and final urine. Among males and females elevation of SS above same sex normals corresponded to composition. As well, treatments that reduced stone rates also reduced these SS values. The degree of calcium phosphate (CaP) admixture was accurately matched by shifting magnitudes of COM and Br SS. As well, increasing CaP content was associated with falling urine citrate and rising urine pH, suggesting renal tubular acidosis. We conclude that sparse urine SS measurements accurately track stone admixtures, and are a reliable index of average renal and urine SS.

Calcium Oxalate↗
PubMed1997

Dependence of upper limit of metastability on supersaturation in nephrolithiasis.

Formation of renal stones requires supersaturation (SS) high enough to induce crystallization; such a SS is referred to as the upper limit of metastability (ULM). The ULM for calcium oxalate (CaOx) or calcium phosphate can be measured by adding oxalate or calcium to urine, respectively, and noting the point at which overt crystallization occurs as evidenced by clouding. In principle, the urine should be more prone to form stone crystals as its SS approaches the ULM, and the SS ULM distance has been used as an index of stone forming potential. In addition, one would expect the ULM and initial SS to be unrelated, as the starting urine SS has no apparent link to the amount of calcium or oxalate that urine can dissolve without leading to crystal formation. However, in rats, we have found a surprising correlation between ULM and SS, such that ULM appears to rise with initial SS, for CaOx, and, to a lesser extent, for brushite (Br), a typical calcium phosphate initial phase. In this study, we measured CaOx and Br ULM, and SS, in urine of 50 patients and 11 normal people, to determine if ULM and SS were correlated, as in rats, and to explore the relationship between SS and ULM. We found the same dependence of ULM on SS as in rats, for both CaOx and Br, and found no differences between patients and normal people with respect to this dependency. However, for Br, patients showed a lower ULM than normals, but the same initial SS, meaning that patients were closer to their crystal formation threshold than normals. Treatments for stones had no apparent effect on the SS-ULM dependency. We conclude that in humans, as in rats, ULM is related to initial SS, and that this relationship is the same in patients as in normals for CaOx, but shifted in a stone forming direction for Br among patients. The ULM-SS interaction is unaffected by contemporary conventional stone treatments, and is more marked for CaOx than Br. The mechanisms of the dependence are unknown. The smaller difference between ULM and initial SS for Br in patients than normal supports prior evidence suggesting a defect in stone patients that could lead to calcium phosphate crystallization, subsequent nucleation of CaOx, and stone disease.

Calcium↗
PubMed2006

Randall's plaque: pathogenesis and role in calcium oxalate nephrolithiasis.

The purpose of these studies was to test the hypothesis that Randall's plaque develops in unique anatomical sites of the kidney and their formation is conditioned by specific stone-forming pathophysiologies. We performed intraoperative papillary biopsies from kidneys of idiopathic-calcium oxalate (CaOx), intestinal bypass for obesity, brushite (BR) and cystine stone formers (SF) during percutaneous nephrolithotomy. Tissues were examined by infrared analysis and light and electron microscopy. Our analysis revealed a distinct pattern of mineral deposition and papillary pathology for each type of SF. CaOx SF had interstitial apatite crystals beginning at thin loops of Henle. These deposits termed Randall's plaque are thought to serve as sites for stone attachment. No tubular injury was noted. Intestinal bypass patients possessed intraluminal apatite deposits in inner medullary collecting ducts (IMCD) with associated cell injury. BR SF showed the most severe form of cortical and medullary changes with sites of Randall's plaque, and yellowish intraluminal deposits of apatite in IMCD. Cystine SF had plugging of ducts of Bellini with cystine crystals and apatite deposits in IMCD and loops of Henle. Intratubular sites of crystalline deposits were always associated to adjacent regions of interstitial fibrosis. The metabolic, anatomic, and surgical pathologic findings in four distinct groups of SF clearly show that 'the histology of the renal papilla from a stone former, is particular to the clinical setting'. We believe our approach to studying stone disease will provide insights into the pathogenesis of stone formation for each type of SF that will lead to improved clinical treatment.

Biopsy↗
PubMed2006

NPT2a gene variation in calcium nephrolithiasis with renal phosphate leak.

A decrease in renal phosphate reabsorption with mild hypophosphatemia (phosphate leak) is found in some hypercalciuric stone-formers. The NPT2a gene encodes a sodium-phosphate cotransporter, located in the proximal tubule, responsible for reclaiming most of the filtered phosphate load in a rate-limiting manner. To determine whether genetic variation of the NPT2a gene is associated with phosphate leak and hypercalciuria in a cohort of 98 pedigrees with multiple hypercalciuric stone-formers, we sequenced the entire cDNA coding region of 28 probands, whose tubular reabsorption of phosphate normalized for the glomerular filtration rate (TmP/GFR) was 0.7 mmol/l or lower. We performed genotype/phenotype correlations for each genetic variant in the entire cohort and expressed NPT2a variant RNAs in Xenopus laevis oocytes to test for cotransporter functionality. We identified several variants in the coding region including an in-frame 21 bp deletion truncating the N-terminal cytoplasmic tail of the protein (91del7), as well as other single-nucleotide polymorphisms that were non-synonymous (A133V and H568Y) or synonymous. Levels of TmP/GFR and urine calcium excretion were similar in heterozygote carriers of NPT2a variants compared to the wild-type (wt) homozygotes. The transport activity of the H568Y mutants was identical to the wt, whereas the N-terminal-truncated version and the 91del7 and A133V mutants presented minor kinetic changes and a reduction in the expression level. Although genetic variants of NPT2a are not rare, they do not seem to be associated with clinically significant renal phosphate or calcium handling anomalies in a large cohort of hypercalciuric stone-forming pedigrees.

Adult↗
PubMed1978

Biochemical and clinical effects of ethane-1-hydroxy-1,1-diphosphonate in calcium nephrolithiasis.

1. The short- and longer-term effects of ethane-1-hydroxy-1,1-diphosphonate (EHDP), an inhibitor of crystal growth and potential preventive agent against urinary tract stones in man, have been studied. 2. Measurement of urinary excretion of EHDP was used to define the best dosage regimen. When 4.4 mmol of EHDP mmol of EHDP was given in four divided doses the murinary concentration of EHDP achieved was high enough (10-5 mol/1) to inhibit the crystallization of calcium crystals throughout the day. 3. Nine patients with recurrent calcium stones were given this dose of EHDP daily for 12 months and seven were then studied for a further 12 months under placebo. During treatment with EHDP, inhibitory activity in urine towards precipitation of calcium phosphate was restored from low values to greatly above normal. This could be accounted for by the inhibitory effect of EHDP itself, coupled with an increase in urinary inorganic pyrophosphate. After stopping EHDP the excretion of EHDP rapidly fell to undetectable levels but the excretion of pryophosphate remained elevated throughout the 12 months of placebo treatment. EHDP also induced a rise in plasma phosphate and an increase in the urinary excretion of oxalic acid and uric acid, but these changes were all fully reversible when EHDP was stopped. 4. The average rate of stone formation per patient per year decreased from 2.4 to 0.2 during treatment with EHDP and remained low during the following 24 months. However, the dose needed for this effect is known to affect bone turnover and mineralization.

Adult↗
PubMed2000

Effects of low animal protein or high-fiber diets on urine composition in calcium nephrolithiasis.

BACKGROUND: The purpose of this article is to evaluate the impact of low protein and high fiber intakes on risk factors of stone recurrence in idiopathic calcium stone formers (ICSFs). METHODS: Ninety-six ICSFs were randomly assigned a low animal protein diet (< 10% of total energy), a high-fiber diet (> 25 g/day), or a usual diet (control group); all patients were recommended to increase their fluid intake. Their daily urine compositions were analyzed at baseline and at four months. Compliance with dietary recommendations was checked by validated food frequency questionnaires. Compliance with total and animal protein intakes was assessed by 24-hour urea and sulfate outputs, respectively. The nutritional intervention (oral instructions, written leaflet, phoning) and food assessment were carried out by a research dietitian. RESULTS: At baseline, diets and the daily urine composition did not differ between the three groups. At four months, while diets differed significantly, the 24-hour output of calcium and oxalate did not differ significantly within and between groups after adjustment for potential confounders (age, sex, and personal and family history of calcium stones) and baseline values. However, as many as 12 out of 31 ICSFs (95% CI, 22 to 58%) assigned to a low animal protein diet achieved a reduction in the urine urea excretion rate of more than 50 mmol/day and also exhibited a significant decrease in urinary calcium excretion that averaged 1.8 mmol/day. A significant correlation between urea and calcium outputs was observed only among patients with hypercalciuria. CONCLUSIONS: These results show that only ICSFs who markedly decrease their animal protein intake, especially those with hypercalciuria, can expect to benefit from dietary recommendations.

Adult↗
PubMed2003

Causes and consequences of kidney loss in patients with nephrolithiasis.

BACKGROUND: It is unknown whether stone formers may safely donate a kidney. Nephrectomy could accelerate stone formation, or loss of filtration with age. We contrast, here, the course of stone patients with two versus one kidney. METHODS: One hundred fifteen patients with a single functioning kidney were compared with 3151 patients with two kidneys. Cause of kidney loss was determined, along with stone types, rates of stone formation, urine stone risk factors, and creatinine clearance. RESULTS: Women were 49.6% of the patients with kidney loss, compared to 33.6% of ordinary stone formers. Obstruction, stone burden, and infection were the most common reasons for kidney loss. We found an increased number of struvite and calcium phosphate stones among single kidney patients. Before and during treatment, single kidney patients had fewer stones than ordinary stone formers. Creatinine clearance was lower in the single kidney patients; rate of loss of kidney function with age was higher among single kidney males versus two kidney males if all patients are considered. Among males >age 45 years, the difference disappears. Females with one and two kidneys lost function with age at equivalent rates. Compared with nonstone formers, male stone formers lose kidney function with age at an accelerated rate. CONCLUSION: Nephrectomy does not worsen stone disease. It may increase loss of renal function among younger males. The pattern of renal function loss with age differs between stone formers and nonstone formers.

Adult↗
PubMed2003

The association between gout and nephrolithiasis in men: The Health Professionals' Follow-Up Study.

Approximately 10 million adults in the United States have experienced the passage of a kidney stone, and up to 5 million have been diagnosed with gout by a physician. Previous reports have suggested that gout increases the risk for the development of kidney stones, but there are no prospective data. We used data from a cohort of 51,529 male health care professionals to examine the independent association between gout and kidney stone disease. In a cross-sectional analysis of gout and kidney stone disease reported on the 1986 baseline questionnaire, the prevalence of kidney stone disease was almost twofold higher in men with history of gout compared to those without (15% vs. 8%). After adjusting for age and body mass index (BMI), a history of gout remained significantly associated with kidney stone disease (OR 1.88; 95% CI 1.68 to 2.11). We then prospectively examined the risk of incident kidney stones in men with and without a confirmed diagnosis of gout after excluding men who reported a history of kidney stone disease or gout on the baseline questionnaire. A confirmed diagnosis of gout increased the multivariate relative risk of incident kidney stones (RR 2.12; 95% CI 1.22 to 3.68). In contrast, a history of kidney stone disease was not associated with increased risk of gout (RR 1.05; 95% CI 0.54 to 2.07). In conclusion, a history of gout independently increases the risk for incident kidney stones in men. Physicians should provide dietary counseling, such as increasing fluid intake and decreasing salt consumption, to subjects with gout in addition to other risk factors, such as family history of kidney stones, in order to decrease the likelihood of stone formation.

Adult↗
PubMed2002

The association between gout and nephrolithiasis: the National Health and Nutrition Examination Survey III, 1988-1994.

BACKGROUND: Gout, an inflammatory arthritis, reportedly afflicts more than 2 million men and women in the United States. Previous reports have suggested an association between gout and kidney stone disease; however, these studies did not adjust for such important potential confounders as obesity and the presence of hypertension. To our knowledge, no published study has examined the independent association between gout and kidney stone disease. METHODS: We used a national probability sample of the US population to determine the independent association between reported gout and history of kidney stone disease. RESULTS: Among men and women 20 years and older, 5.6% (10 million) reported the previous passage of a kidney stone and 2.7% (5.1 million) reported a diagnosis of gout by a physician. Moreover, 8.6% of individuals who reported the passage of a kidney stone on two or more occasions had a history of gout. Conversely, the prevalence of previous kidney stones in subjects with reported gout was 13.9%. In the age-adjusted model, gout was associated with an increased odds ratio (OR) for previous kidney stones (OR, 1.97; 95% confidence interval [CI], 1.37 to 2.83). After further adjustment for sex, race, body mass index, and presence of hypertension, the OR for previous kidney stones in individuals with gout decreased to 1.49 (95% CI, 1.04 to 2.14). CONCLUSION: Showing an independent association between kidney stone disease and gout strongly suggests that they share common underlying pathophysiological mechanisms. Identification of these mechanisms may lead to improved preventive strategies for both conditions.

Adolescent↗