Fractional excretion of sodium

定义

Fractional excretion of sodium is the amount of salt (sodium) that leaves the body through urine compared to the amount filtered 和 reabsorbed by the kidney.

Fractional excretion of sodium (FENa) is not a test. Instead it is a calculation based on the concentrations of sodium 和 creatinine in the blood 和 urine. 尿液 和 血液化学 tests are needed to perform this calculation.

选择的名字

FE sodium; FENa

How the Test is Performed

血 和 尿液样本 are collected at the same time 和 sent to a lab. There, they are examined for salt (sodium) 和 creatinine levels. Creatinine is a chemical waste product of creatine. Creatine is a chemical made by the body 和 is used to supply energy mainly to muscles.

How to Prepare for the Test

Eat your normal foods with a normal amount of salt, unless otherwise instructed by your health care provider.

If needed, you may be told to temporarily stop medicines that interfere with test results. For example, some diuretic medicines (water pills) can affect test results.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

The test is usually done for people who are very ill with acute kidney disease. The test helps determine if the drop in urine production is due to reduced blood flow to the kidney or to kidney damage itself.

What Abnormal Results Mean

A meaningful interpretation of the test can be made only when your urine volume has dropped to less than 500 mL/day.

FENa of lower than 1% indicates decreased blood flow to the kidney. This can occur with kidney damage due to 脱水 or 心脏衰竭.

FENa higher than 1% suggests damage to the kidney itself.

风险

There are no risks with providing the urine sample.

There is little risk involved with having your blood taken. Veins 和 arteries vary in size from one person to another 和 from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks of having blood drawn are slight, but may include:

• 大出血
• Multiple punctures to locate veins
• Fainting or feeling lightheaded
• 血 accumulating under the skin (hematoma)
• Infection (a slight risk any time the skin is broken)

参考文献。

Parikh CR, Koyner JL. Biomarkers in acute 和 chronic kidney diseases. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner 和 Rector's The Kidney. 11日艾德. Philadelphia, PA: Elsevier; 2020:chap 27.

Polonsky TS, Bakris GL. Alterations in kidney function associated with 心脏衰竭. In: Felker GM, Mann DL, eds. Heart Failure: A Companion to Braunwald's Heart Disease. 第四版. Philadelphia, PA: Elsevier; 2020:chap 15.