Halperin M L, Skorecki K L
Am J Nephrol. 1986;6(4):241-5. doi: 10.1159/000167170.
To evaluate urinary solutes in terms of their effect on body fluid tonicity, it is necessary to consider: whether that solute serves as an effective osmole in terms of ECF-ICF fluid shifts, its ability to accumulate in the body even if it is an osmotically effective particle, and the original number of body particles from which it derived. Thus, urea can be excluded since it is an ineffective osmole and only urine cations and anions need be considered. With respect to the former, one must separate the proportion of dietary versus endogenous potassium in this analysis as their effects differ. With respect to urine anions, urine chloride need not contribute to the loss of 'particles that count' when its excretion is accompanied by ammonium (i.e. equivalent to a bicarbonate gain). Thus, in the example cited at the beginning of this article, the excretion of hyperosmolar urine may not change body fluid tonicity if all the urinary potassium was of dietary origin and all the bicarbonate generated was retained as such. Finally, it is necessary to integrate defence of ECF volume (sodium balance), potassium balance, acid-base balance and intercompartmental fluid shifts to understand the overall renal response to defend tonicity. While there is utility in measuring urinary osmolality (assessment of medullary physiology, ADH action, water abstraction, concentrating power), in situations where body fluid tonicity is deranged, it is necessary to evaluate the urine sodium concentration along with the concentration of other solutes which may serve as effective osmoles in the urine.
为了根据尿溶质对体液张力的影响来评估它们，有必要考虑：就细胞外液-细胞内液的液体转移而言，该溶质是否作为一种有效的渗透分子，即使它是一种具有渗透活性的粒子，其在体内蓄积的能力，以及它所源自的体内粒子的原始数量。因此，尿素可以被排除，因为它是一种无效的渗透分子，只需考虑尿中的阳离子和阴离子。关于前者，在这个分析中必须区分饮食中钾与内源性钾的比例，因为它们的作用不同。关于尿阴离子，当尿氯的排泄伴有铵（即相当于碳酸氢盐增加）时，它对“有意义的粒子”的丢失没有贡献。因此，在本文开头引用的例子中，如果所有尿钾都来自饮食，并且所有生成的碳酸氢盐都原样保留，那么高渗尿的排泄可能不会改变体液张力。最后，有必要综合细胞外液容量（钠平衡）、钾平衡、酸碱平衡和跨腔室液体转移的调节，以了解肾脏维持张力的整体反应。虽然测量尿渗透压（评估髓质生理学、抗利尿激素作用、水重吸收、浓缩能力）有一定作用，但在体液张力紊乱的情况下，有必要评估尿钠浓度以及尿中可能作为有效渗透分子的其他溶质的浓度。
