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.

中文翻译：

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外科医生在尿结石成分化学研究中的作用。

尿石的化学分析通常被解释为“石头的成分”。但是，必须考虑到，在大多数情况下，只有一块石头被送到了实验室。在一些复发的患者中，结石的成分在发作之间变化很大，或者从结石碎片获得的分析结果与当前的24小时尿液分析或尿液pH记录数据不符。产生的问题是，这种结果是否可能是不正确的石头采样方案的结果。在由两个矿物相组成的简单分层2D石头模型中，显示了碎石过程的选择如何影响“石头组成”的结果。根据碎片在整个石头中的初始位置，各个计算出的分析结果可能与整个石材的组成以及两个碎片之间存在很大差异。即使在定义条件下“生长”的2D-2-组件模型的简化条件下，从一块石头中提取的不同样本的分析之间的差异也部分是显着的。如果研究真正的3D-尿石，这些差异会增加。进一步的采样偏差可能会演变并增加正确采样的问题：例如，如果在ESWL或基于激光的碎石（“除尘”）时尿路石的高抵抗力部位保持完好无损，则脆弱的部位会完全崩解并从体内移出细颗粒污泥—尽管其成分可能携带有关石材发病机理的重要信息，但仍损失了石材的细小部分。所以，仅从较硬的残留物中获得的“结石分析”显示出不完整的结果，这一事实原则上限制了其临床解释。碎石的选择至关重要。不应低估由潜在选择偏差引起的分析不确定性的程度。因此，抽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所犯的错误将影响分析结果，从而影响对潜在发病机制的澄清。这可能会导致不正确的代谢策略，从而可能导致结石复发，而这本可以避免的。建议使用内窥镜检查方法分析尿结石的决策方案。