Department of Urology, Marienhaus Kliniken GmbH, Krankenhaus Maria Hilf, Dahlienweg 3, 53474, Bad Neuenahr-Ahrweiler, Germany.
FB Medizintechnik und Technomathematik, FH Aachen, Campus Jülich, 52428, Jülich, Germany.
Urolithiasis. 2020 Oct;48(5):435-441. doi: 10.1007/s00240-020-01195-6. Epub 2020 May 20.
The chemical analysis of an urolith is often interpreted as "stone's composition". However, it must be taken into consideration, that in most cases, only a fragment of the stone has been sent to the laboratory. In some recurrent patients, stone compositions either vary considerably between episodes or the analytical result obtained from the stone fragment does not fit with the data of e.g. current 24 h-urinalysis or urinary pH-records. The question arises, whether this outcome may be the result of an improper stone sampling scheme. On a simple layered 2D-stone model composed of two mineral phases it is shown, how the choice of a stone fragment process may influence the result of "stone composition". Depending on the initial position of fragment within the whole stone, the respective calculated analyses can relevantly differ from the whole stone composition as well as strongly between two fragments. Even under the simplified conditions of a 2D-2-component-model "grown" under defined conditions, the differences between the analyses of the different specimens taken from a stone are in part remarkable. The more it can be argued that these differences increase if a real 3D-urolith is investigated. Further sampling biases may evolve and increase the problem of proper sampling:, e.g., if an urolith's more resistant parts remain intact while ESWL or laser-based stone fragmentation ("dusting"), the weak parts became fully disintegrated and removed from the body as fine-grained sludge-the stone's fine fraction is lost although its composition may carry important information on the stone's pathogenesis. Consequently, a "stone analysis" only obtained from the harder remains reveals an incomplete result, a fact that in principle limits its clinical interpretation. Choice of stone fragment is crucial. The extent of the uncertainty of an analysis resulting from potential selection biases should not be underestimated. Thus, sampling should be considered as an important part of the processes of quality assurance and management. Errors made at this early stage of diagnosis finding will affect the analytical result and thus influence the clarification of the underlying pathomechanism. This can lead to an improper metaphylactic strategy potentially causing recurrent stone formation which otherwise would have been prevented. A decision scheme for analysis of urinary stones removed using endoscopic methods is suggested.
尿石的化学分析通常被解释为“结石的成分”。然而，必须考虑到，在大多数情况下，送到实验室的只是结石的一个碎片。在一些复发性患者中，结石成分在不同发作之间差异很大，或者从结石碎片获得的分析结果与例如当前 24 小时尿液分析或尿液 pH 记录的数据不相符。由此产生一个问题，即这种结果是否可能是由于结石取样方案不当所致。在一个由两种矿物质组成的简单分层二维结石模型上，我们展示了选择结石碎片处理方式如何影响“结石成分”的结果。根据碎片在整个结石中的初始位置，各自计算的分析结果可能与整个结石成分以及两个碎片之间存在显著差异。即使在定义条件下“生长”的二维两成分模型的简化条件下，从结石中取出的不同标本之间的分析差异在某些部分也是显著的。如果研究一个真实的 3D 尿石，这些差异可能会增加，理由就越充分。进一步的采样偏差可能会出现并增加适当采样的问题：例如，如果尿石的更坚固部分在体外冲击波碎石术或基于激光的结石碎裂（“碎石”）过程中保持完整，而较弱的部分则完全分解并从体内排出作为细颗粒污泥——尽管结石的精细部分可能携带有关结石发病机制的重要信息，但仍会丢失。因此，仅从较硬的残留物中获得的“结石分析”会得出不完整的结果，这一事实原则上限制了其临床解释。结石碎片的选择至关重要。由于潜在的选择偏差导致分析的不确定性程度不应被低估。因此，采样应被视为质量保证和管理过程的重要组成部分。在诊断发现的早期阶段出现的错误会影响分析结果，从而影响对潜在发病机制的澄清。这可能导致不适当的预防复发策略，从而导致潜在的结石形成复发，否则这种情况本可以预防。建议使用内镜方法取出的尿石分析的分析方案。
