Kok D J, Khan S R
Department of Pathology, University of Florida, Gainesville.
Kidney Int. 1994 Sep;46(3):847-54. doi: 10.1038/ki.1994.341.
The chances of stone formation occurring through a free particle mechanism were calculated using the approach of Finlayson and Reid [1]. For these calculations we used new data on nephron dimensions, supersaturation and crystal growth rates in urine, and also incorporated the size increasing effect of crystal agglomeration. The calculations were performed assuming different levels of oxalate excretion, simulating the diurnal variation and acute hyperoxaluria following a dietary load. In addition urinary flow conditions were varied according to changes in daily urinary volume. It is shown that during the normal transit time of urine through the nephron, particles can obtain a size big enough to be retained in the nephron. This is mainly due to the size-increasing effect of the agglomeration process. The precipitable amount of oxalate present is not limiting for the maximum attainable particle size. However, acute increases in oxalate excretion do pose a risk because supersaturation is reached earlier in the nephron and consequently the crystal particles are allowed more time to increase in size. In conclusion, the present calculations demonstrate that during the normal transit time through the kidney, crystalline particles can be formed which are large enough to be retained because of their size and thus form the nidus of a stone. The highest risk is encountered at the end of those collecting ducts where crystals formed in nephrons with a long loop of Henle meet and agglomerate.
采用芬利森和里德[1]的方法计算了通过自由颗粒机制形成结石的可能性。在这些计算中，我们使用了关于肾单位尺寸、尿液中的过饱和度和晶体生长速率的新数据，并且还纳入了晶体团聚的尺寸增大效应。计算是在假设不同草酸盐排泄水平的情况下进行的，模拟饮食负荷后的昼夜变化和急性高草酸尿症。此外，尿流条件根据每日尿量的变化而改变。结果表明，在尿液正常通过肾单位的时间内，颗粒能够获得足够大的尺寸以保留在肾单位中。这主要是由于团聚过程的尺寸增大效应。草酸盐的可沉淀量对于可达到的最大颗粒尺寸并非限制因素。然而，草酸盐排泄的急性增加确实带来风险，因为在肾单位中更早达到过饱和度，因此晶体颗粒有更多时间增大尺寸。总之，目前的计算表明，在正常通过肾脏的时间内，可以形成足够大的晶体颗粒，因其尺寸而被保留，从而形成结石的核心。在那些亨氏袢长的肾单位中形成的晶体在集合管末端相遇并团聚的地方，风险最高。
