Background

Pediatric nephrologists use kidney length and kidney volume z-scores to longitudinally assess normal nephron endowment. However, most radiologists only report kidney length. Agreement between kidney length and kidney volume z-scores in children has been understudied. This study aims to assess agreement between kidney length and kidney volume z-scores in children.

Methods

This novel cross-sectional cohort study prospectively followed prematurely born babies from a large specialized prematurity follow-up center. A healthy control group matched the cases by age and sex and was recruited from schools. Children were assessed for kidney length and kidney volumes at age 5 by three independent ultrasonographers. All measurements were performed in triplicate. Detailed anthropometry, blood pressure, and kidney function were also obtained. Age-independent z-scores were calculated for all parameters according to Scholbach and Weitzel and compared using descriptive statistics.

Results

We studied 89 premature patients (median 32 weeks gestational age) and 33 healthy controls (median 38 weeks gestational age). There were 732 determinations of kidney length, width, and thickness. The mean z-score of the right kidney length was 0.65 ± 0.08 (SEM) compared with 0.88 ± 0.08 of the left kidney length (p = 0.0003, two-sided paired t test). The squared correlation coefficient for kidney volume to kidney length was 0.32 (p < 0.0001). Bland and Altman analysis revealed considerable bias with − 1.36 ± 0.76 standard deviations and 95% limits of agreement from − 2.83 to − 0.16.

Conclusion

Reporting only kidney length results in significant overestimation of age-independent z-scores. Based on our findings, consideration to measuring all kidney dimensions may be more appropriate.

中文翻译：

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肾脏体积和肾脏长度 z 分数之间的一致性低

背景

儿科肾病学家使用肾脏长度和肾脏体积 z 分数来纵向评估正常的肾单位禀赋。然而，大多数放射科医生只报告肾脏长度。儿童肾脏长度和肾脏体积 z 分数之间的一致性尚未得到充分研究。本研究旨在评估儿童肾脏长度和肾脏体积 z 分数之间的一致性。

方法

这项新颖的横断面队列研究前瞻性地跟踪了来自大型专业早产儿随访中心的早产儿。健康对照组按年龄和性别匹配病例，并从学校招募。三位独立的超声检查人员在 5 岁时评估儿童的肾脏长度和肾脏体积。所有测量一式三份进行。还获得了详细的人体测量学、血压和肾功能。根据 Scholbach 和 Weitzel 计算所有参数的与年龄无关的 z 分数，并使用描述性统计数据进行比较。

结果

我们研究了 89 名早产患者（中位胎龄 32 周）和 33 名健康对照（中位胎龄 38 周）。对肾脏长度、宽度和厚度进行了 732 次测定。右肾长度的平均 z 评分为 0.65 ± 0.08 (SEM)，而左肾长度为 0.88 ± 0.08 ( p = 0.0003，双边配对t检验)。肾脏体积与肾脏长度的平方相关系数为 0.32 ( p < 0.0001)。Bland 和 Altman 分析揭示了相当大的偏差，标准偏差为 - 1.36 ± 0.76，95% 的一致性限制为 - 2.83 至 - 0.16。

结论

仅报告肾脏长度会导致显着高估与年龄无关的 z 分数。根据我们的发现，考虑测量所有肾脏尺寸可能更合适。