A study on calcium oxalate monohydrate renal uroliths. II. Fine inner structure

Human kidney stones: a natural record of universal biomineralization

GeoBioMed - a new transdisciplinary approach that integrates the fields of geology, biology and medicine - reveals that kidney stones composed of calcium-rich minerals precipitate from a continuum of repeated events of crystallization, dissolution and recrystallization that result from the same fundamental natural processes that have governed billions of years of biomineralization on Earth. This contextual change in our understanding of renal stone formation opens fundamentally new avenues of human kidney stone investigation that include analyses of crystalline structure and stratigraphy, diagenetic phase transitions, and paragenetic sequences across broad length scales from hundreds of nanometres to centimetres (five Powers of 10). This paradigm shift has also enabled the development of a new kidney stone classification scheme according to thermodynamic energetics and crystalline architecture. Evidence suggests that ≥50% of the total volume of individual stones have undergone repeated in vivo dissolution and recrystallization. Amorphous calcium phosphate and hydroxyapatite spherules coalesce to form planar concentric zoning and sector zones that indicate disequilibrium precipitation. In addition, calcium oxalate dihydrate and calcium oxalate monohydrate crystal aggregates exhibit high-frequency organic-matter-rich and mineral-rich nanolayering that is orders of magnitude higher than layering observed in analogous coral reef, Roman aqueduct, cave, deep subsurface and hot-spring deposits. This higher frequency nanolayering represents the unique microenvironment of the kidney in which potent crystallization promoters and inhibitors are working in opposition. These GeoBioMed insights identify previously unexplored strategies for development and testing of new clinical therapies for the prevention and treatment of kidney stones.

Two novel AGXT mutations identified in primary hyperoxaluria type-1 and distinct morphological and structural difference in kidney stones

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease characterized by excessive oxalate accumulation in plasma and urine, resulting in various phenotypes because of allelic and clinical heterogeneity. This study aimed to detect disease-associated genetic mutations in three PH1 patients in a Chinese family. All AGXT exons and 3 common polymorphisms which might synergistically interact with mutations, including P11L, I340 M and IVSI+74 bp were analyzed by direct sequencing in all family members. It demonstrated that in each of three patients, a previously reported nonsense mutation p.R333^* was in cis with a novel missense mutation p.M49L in the minor allele characterized by the polymorphism of 74-bp duplication in intron 1, while the other novel missense mutation p.N72I was in trans with both p.R333^* and P.M49L in the major allele. Kidney stones from two sibling patients were also observed though stereomicroscopic examination and scanning electron microscopy. Distinct morphological and inner-structure differences in calculi were noticed, suggesting clinical heterozygosity of PH1 to a certain extent. In brief, two novel missense mutations were identified probably in association with PH1, a finding which should provide an accurate tool for prenatal diagnosis, genetic counseling and screening for potential presymptomatic individuals.

Ultrastructure of selected calcium oxalate-containing urinary calculi from dogs

OBJECTIVE

To elucidate the ultrastructural details of calcium oxalate-containing urinary calculi from dogs. Sample Population-38 specimens selected from a collection of 8,297 oxalate-containing urinary calculi from dogs: 22 specimens composed of calcium oxalate (calcium oxalate monohydrate [COM], calcium oxalate dihydrate [COD], or COM and COD) and 16 specimens composed of calcium oxalate with amorphous calcium phosphate.

PROCEDURE

Analyses of specimens included use of plain, reflected, and polarized light microscopy, X-ray diffractometry, scanning electron microscopy (SEM) with backscattered electron (BSE) imagery, and electron microprobe analysis.

RESULTS

Four texture types were observed in calcium oxalate calculi; 4 texture types of calcium oxalate-calcium phosphate-mixed calculi were recognized. Texture types were delineated through differences in calcium oxalate crystal sizes, which were affected by urine supersaturation and abundance of crystal nucleation sites. Segregation of calcium oxalate from calcium phosphate indicated they do not precipitate under the same conditions. Deposition of calcium phosphate between calcium oxalate crystals decreased the volume of pore spaces within calculi. Porosity was observed along boundaries between COM and COD. Minute pores increased the surface area of calculi exposed to urine, and this increase in liquid-solid interface promotes interaction of crystals with the surrounding urine.

CONCLUSIONS AND CLINICAL RELEVANCE

Calcium oxalate urolithiasis is of major concern, because it is often a recurrent disease among dogs, principally treated by surgical removal of calculi, with few effective dissolution strategies. Understanding the ultrastructure and mineralogic content of calcium oxalate and its association with amorphous calcium phosphate is a step toward the solution of this increasingly important medical problem.

Study on calcium oxalate monohydrate renal uroliths. III. Composition and density

Density and content of mineral constituents were determined for 33 human calcium oxalate monohydrate (hereafter COM) uroliths whose external appearance and inner structure were described in part I and II respectively. Studied stones contained 0.13-0.42 wt.% of struvite, 0.68-4.12 wt.% of hydroxyapatite, 73-96 wt.% of COM and 3-10 wt.% of water unbound in a crystallohydrate 10 to 20 wt.% of calculus mass is not accounted for by chemical analysis. Density of COM calculi varying between 1.67 and 2.06 g cm-3 is not a function of any single stone parameter. Around 30% of stone volume is not occupied by crystalline components. The mulberry stones of sedimentary origin contained higher amount of organic matter than papillar and mulberry stones displaying site of attachment to epithelium.