Department of Paediatric Nephrology, Children's Clinical Hospital, Medical University of Bialystok, Bialystok, Poland.
Faculty of Health Sciences, Lomza State University of Applied Sciences, Lomza, Poland.
Urolithiasis. 2019 Apr;47(2):155-163. doi: 10.1007/s00240-018-1041-2. Epub 2018 Jan 22.
High fluid intake has been universally recommended for kidney stone prophylaxis. We evaluated 24-h urine osmolality regarded as the best biomarker of optimal hydration and upper metastable limit osmolality after water evaporation from urine sample to the onset of spontaneous crystallization and its usefulness as a new risk index that would describe an individual lithogenic potential. We collected 24-h urine from 257 pediatric patients with kidney stones and 270 controls. After volume and osmolality assessment, the urine samples were subjected to volume reduction in vacuum rotavapor continued to the onset of an induced urinary crystallization. The upper metastable limit osmolality of urine sample was calculated based on its initial osmolality value and the amount of water reduction. Pediatric stone formers presented with higher urine volume and lower urine osmolality than healthy controls. Despite that, their urine samples required much lower volume reduction to induce the spontaneous crystallization than those of controls. The ROC analysis revealed an AUC for the upper metastable limit osmolality of 0.9300 (95% CI 0.9104-0.9496) for distinguishing between stone formers and healthy subjects. At the cutoff of 2696 mOsm/kg, the test provided sensitivity and specificity of 0.8638 and 0.8189, respectively. 24-h urine osmolality provided the information about current hydration status, whereas evaporation test estimated the urinary potential to crystalize dependent on urine composition. Upper metastable limit osmolality may estimate the individual lithogenic capability and identify people at risk to stone formation when exposed to dehydration.
高液体摄入量已被普遍推荐用于预防肾结石。我们评估了 24 小时尿液渗透压，它被认为是最佳水化的最佳生物标志物和尿液样本蒸发后自发结晶的上亚稳渗透压极限，并评估了其作为新风险指数的有用性，该指数可描述个体成石潜力。我们收集了 257 名肾结石患儿和 270 名对照者的 24 小时尿液。在评估体积和渗透压后，将尿液样本在真空中进行旋转蒸发，直至尿液开始自发结晶。根据初始渗透压值和减少的水量计算尿液样本的上亚稳渗透压极限。与健康对照组相比，儿科结石患者的尿量较高，尿液渗透压较低。尽管如此，与对照组相比，他们的尿液样本需要更少的体积减少才能诱导自发结晶。ROC 分析显示，上亚稳渗透压极限的 AUC 为 0.9300（95%CI 0.9104-0.9496），用于区分结石形成者和健康受试者。在 2696 mOsm/kg 的截止值下，该检测的敏感性和特异性分别为 0.8638 和 0.8189。24 小时尿液渗透压提供了当前水化状态的信息，而蒸发试验则估计了尿液成分依赖于尿液结晶的潜力。上亚稳渗透压极限可以估计个体的成石能力，并在暴露于脱水时识别有结石形成风险的人。
