Kidney stones probably grow during crystalluria by crystal sedimentation and aggregation (AGN) on stone surfaces. This process\r\nhas to occur within urinary transit time (UT) through the kidney before crystals are washed out by diuresis. To get more\r\ninformation, we studied by spectrophotometry the formation and AGN of Ca oxalate (Ca Ox) crystals which were directly\r\nproduced in urine of 30 stone patients and 30 controls by an oxalate (Ox) titration. Some tests were also performed after removing\r\nurinary macromolecules (UMs) by ultrafiltration. To induce rapid crystallization, high Ox additions (0.5ââ?¬â??0.8mM) were necessary.\r\nThe most important finding was retardation of crystal AGN by UM. In urine of 63% of controls but only 33% of patients, no AGN\r\nwas observed during an observation of 60 minutes (P < 0.05). Also growth and sedimentation rate of crystals were significantly\r\nreduced by UM. For stone metaphylaxis, especially for posttreatment residuals, avoiding dietary Ox excesses to prevent crystal\r\nformation in the kidney and increasing diuresis to wash out crystals before they aggregate are recommended.
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