The primary and absolute requisite for calcium-oxalate stone formation - supersaturation of urine with this salt - is satisfied under normal conditions in stone formers and healthy subjects alike. This is manifested in both groups as the passage of calcium-oxalate crystals in the urine. The fact that the majority of us do not, as a consequence, succumb to the disease has been ascribed to the presence in urine of inhibitors which prevent the progression from crystal nucleation to crystal growth and crystal aggregation. These three separate phenomena are commonly collected under the single title of crystallization. The obvious extension to the presumed existence of natural inhibitors of crystallization in urine is that the occurrence of stones can be regarded as the direct result of their lack or deficiency in urine from stone formers. In accord with this so-called ‘inhibitor theory’, it has been observed that crystals of calcium oxalate occur more frequently in the urine of stone formers and that, moreover, they are larger and more highly aggregated than those excreted in the urine of individuals who have never formed a stone. While this theory has been largely accepted as a feasible, although as yet unproved, explanation for the formation of stones, an alternative ‘promoter’ hypothesis has also been given serious consideration. This states that urines from afflicted individuals, rather than lacking inhibitors (or, perhaps, in addition to such a lack), contain substances which promote crystallization.
KeywordsStone Formation Calcium Oxalate Crystal Nucleation Calcium Oxalate Crystal Pentosan Polysulfate
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