Kamel K S, Ethier J H, Richardson R M, Bear R A, Halperin M L
Department of Medicine, St. Michael's Hospital, Toronto, Ont., Canada.
Am J Nephrol. 1990;10(2):89-102. doi: 10.1159/000168062.
The purpose of this review is to provide an update on the use of the urine electrolyte and osmolality measurements in patients with disorders of fluid, electrolytes, and/or acid-base metabolism. It is critical to appreciate that there are no 'normal values' for these parameters, only 'expected values' relative to clinical situations. Pitfalls in the interpretation of each electrolyte in the urine are also provided. To detect a mild to moderate degree of reduction of the 'effective' intravascular volume, both urine sodium (Na) and chloride (Cl) concentrations should be measured. Pitfalls in this assessment are abnormal renal and adrenal function and the use of diuretics. Insights into the etiology of the low 'effective' intravascular volume can be deduced by comparing the urine Na, potassium (K), and Cl concentrations. The urine net charge (Cl vs. Na + K) is the most reliable way to estimate the urine ammonium concentration short of its direct measurement, an assay that is not provided by most laboratories. This measurement is important in the differential diagnosis of hyperchloremic metabolic acidosis. To examine the renal response to hypokalemia or hyperkalemia, the two components of K excretion (K secretion and urine flow rate) should be examined separately. The former is evaluated using the transtubular K, concentration gradient. The urine osmolality is used to assess antidiuretic hormone action and the osmolality of the renal medulla and to determine the etiology of polyuria and/or hypernatremia. The urine osmolality can also be used to assess the ammonium concentration, using the urine osmolal gap, and to detect unusual urine osmoles.
本综述的目的是更新尿液电解质和渗透压测量在液体、电解质及/或酸碱代谢紊乱患者中的应用情况。必须认识到，这些参数没有“正常值”，只有相对于临床情况的“预期值”。文中还介绍了尿液中各电解质解读的陷阱。为检测“有效”血管内容量的轻度至中度减少，应同时测量尿钠（Na）和氯（Cl）浓度。该评估的陷阱包括肾功能和肾上腺功能异常以及利尿剂的使用。通过比较尿Na、钾（K）和Cl浓度，可推断出低“有效”血管内容量的病因。尿净电荷（Cl与Na + K之比）是在无法直接测量尿铵浓度（大多数实验室不提供该检测）的情况下估算尿铵浓度最可靠的方法。该测量在高氯性代谢性酸中毒的鉴别诊断中很重要。为检查肾脏对低钾血症或高钾血症的反应，应分别检查钾排泄的两个组成部分（钾分泌和尿流率）。前者使用跨肾小管钾浓度梯度进行评估。尿渗透压用于评估抗利尿激素的作用和肾髓质的渗透压，并确定多尿和/或高钠血症的病因。尿渗透压还可用于利用尿渗透压间隙评估铵浓度，并检测异常的尿渗透溶质。
