| Background and Objectives There are still lack of an effective method for preventing urinary stone formation which with a high prevalence rate and high recurrent rate. Some authors reported that appropriate drugs and dietary management that used after evaluating patients'metabolism according to 24-hour urine for urinary stone risk factors could decrease the stone recurrent rate. However, the outcome of 24-hour urine analysis for stone risk factors may be influenced by some factors such as bacteria because of its long collection period and complex contents. So, it is very important to find an ideal way of preserving 24-hour urine for evaluating patients'metabolism objectively and stone prevention. The aim of this study is to compare the efficacy of different preserving methods for 24-hour urine sample used for stone risk factors analysis and evaluate the accuracy of evaluating person's metabolism by a single 24-hour urine sample.Materials and Methods 1. From May 2010 to June 2010, spot urines of 22 patients were obtained for calcium, oxalate, citrate, phosphate, uric acid, magnesium, sodium and potassium analysis. Then the residual urines were divided into normal temperature group and 4℃group which contained 5 urine specimens with 10ml per sample respectively. And 0.2g thymol, 100μl methylbenzene, 100μl hydrochloric acid (6mmol/L), 100μl sodium azide(0.3mmol/L) were respectively added to the urine specimens for each group while one sample without preservation. Then the two groups were saved at normal temperature and 4℃respectively. After 24-hour and 48-hour, calcium, oxalate, citrate, phosphate, uric acid, magnesium, sodium and potassium of the urine were examined and compared.2. From December 2010 to April 2011, 35 adult volunteers were enrolled in this study for collecting 3 consecutive 24-hour urines under self-selected diets, which were used for calcium, oxalate, citrate, phosphate, uric acid, magnesium, sodium and potassium analysis. Then the variations of stone risk factors were compared for each day.Results 1.After 24-hour and 48-hour, there was a significant statistic difference (P=0.013) between specimens preserved with hydrochloric acid and without any preservation for citrate in the normal temperature group and 4℃group. However, there was no significant statistic difference among specimens preserved with thymol, methylbenzene or without any preservation for citrate meanwhile there were also no significant statistic difference among specimens preserved with thymol, methylbenzene and hydrochloric acid in the normal temperature group and 4℃group. For the other risk factors including calcium, oxalate, phosphate, uric acid, magnesium, sodium and potassium, there was no significant statistic difference among the specimens preserved with thymol, methylbenzene, hydrochloric acid, sodium azide or without preservation in the normal temperature group and 4℃group when saved for 24-hour and 48-hour.2. For 24-hour urines of the 35 adult volunteers, there was a significant statistic difference for calcium and magnesium between the first day and the third day, and the P value was 0.007 and 0.045 respectively. But for the first and the second day or the second and the third day, there was no significant statistic difference for the two risk factors. And for the other risk factors, including oxalate, phosphate, uric acid, sodium and potassium, the excretion of 24-hour urines were so stable that there was no significant statistic difference during the 3 days.Conclusions 1. After preserved with thymol, methylbenzene, hydrochloric acid/sodium azide or without preservation for 24-hour and 48-hour in the normal temperature and 4℃, there was no significant statistic difference for calcium, oxalate, phosphate, uric acid, magnesium, sodium and potassium in urine specimens. But for citrate, there was a significant statistic difference (P=0.013) between specimens preserved with hydrochloric acid and without any preservation. However, there was no significant statistic difference among specimens preserved with thymol, methylbenzene or without any preservation for citrate meanwhile there were also no significant statistic difference among specimens preserved with thymol, methylbenzene and hydrochloric acid in the normal temperature group and 4℃group. So the result of 24-hour urine stone risk factors analysis preserved by thymol or methylbenzene may present the metabolism level precisely.2. With self-selected diets, the secretion of oxalate, phosphate, uric acid, citrate, sodium and potassium of 24-hour uine was so stable that there was no significant statistic difference of variations for each day. For calcium and magnesium, there was a significant statistic difference of variations but without clinical significance. So, the evaluation of person's metabolism for stone risk factors by a single 24-hour urine is precise. |
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