Crystalluria: A Valuable Parameter in the Study of Urolithiasis
The finding of crystals in the urinary sediment is of no clinical importance when their number is low and no aggregates are formed. Crystals can occasionally be formed in urines in normal individuals in the absence of any significant and persistent physico-chemical abnormality.
Precipitation and crystallization are indeed constantly secondary to urinary changes (pH variations, decrease of inhibitory power, hyperconcentration) leading to supersaturation. Crystalluria is strictly dependent upon urinary supersaturation. Crystal formation is an obligatory intermediate step between physico-chemical alterations and calculus formation.
From a study of crystalluria that we have conducted in a group of 50 patients suffering from various types of urolithiasis, as well as in a group of normal subjects as controls, interesting results have emerged with regard to volume and aggregation of crystals.
In recurrent stone-formers crystals are usually greater than 150 – 200 µ, whereas in patients having had a single episode of lithiasis, crystals only rarely exceed 100 µ.
Morphologic and ultrastructural analysis of crystals and of crystal aggregates has often revealed epitaxial and dendritic growth patterns.
In addition, crystalluria has been investigated with regard to diurnal variations. A circadian rhythm in crystal excretion has been frequently but not constantly found, involving variations in the number, volume and morphologic features of crystal phases.
Crystalluria is therefore a reliable index of urinary supersaturation (or of lack of inhibitory factors), thereby representing a valuable prognostic marker.
KeywordsCrystallization Filtration Oxalate Naphthalene Refraction
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