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急性肾损伤(急性肾衰竭)时的钠、尿素和其他分子的排泄分数

Authors
Rasheed A Balogun, MD
Mark D Okusa, MD
Section Editor
Paul M Palevsky, MD
Deputy Editor
Alice M Sheridan, MD
Translators
李超, 主治医师

引言

钠排泄分数(fractional excretion of sodium, FENa)是指排泄至尿中的滤过钠的百分比。急性肾损伤(acute kidney injury, AKI)，以前称为急性肾衰竭，FENa的测定结果被广泛用于鉴别AKI的原因，即是肾前性疾病(肾脏低灌注下降)所致，还是急性肾小管坏死(acute tubular necrosis, ATN)造成。(参见“急性肾损伤(急性肾衰竭)中肾前性疾病与急性肾小管坏死的病因与诊断”，关于‘评估和诊断’一节)

如下所述，FENa在AKI患者中的应用具有许多局限性，包括：定义肾前性疾病的FENa会随肾小球滤过率(glomerular filtration rate, GFR)的不同而变化，除肾前性疾病外还有多种病因可导致低FENa，如果存在肾性耗盐(如利尿治疗)时应用钠排泄的测定可能具有误导性。因此，AKI的病因诊断应基于患者的总体表现，包括病史、临床检查、尿镜检，以及对容量复苏的反应，而不是仅仅依靠FENa。当利尿剂仍具有活性且FENa不低时，测定尿素排泄分数(fractional excretion of urea, FEUrea)可能会有所帮助。(参见下文‘FENa的局限性’和‘尿素’)

尽管尚未在临床广泛应用，但用于评估实质性肾小管损伤的新的尿和血清生物标志物目前已在验证中[1]。(参见“急性肾损伤(急性肾衰竭)中肾前性疾病与急性肾小管坏死的病因与诊断”，关于‘评估和诊断’一节)

公式 — 钠滤过负荷可由GFR(由肌酐清除率估算得出)和血清钠浓度(serum sodium concentration, SNa)的乘积所确定。另一方面，尿钠排泄量则由尿钠浓度(urine sodium concentration, UNa)乘以尿量(V)得出。公式如下：

                                                         UNa   x   V
         FENa, percent    =      ——————————————————    x    100
                                           SNa   x   [(UCr  x  V)  ÷  SCr]

               

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Literature review current through: 2017-06 . | This topic last updated: 2017-05-26.
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