Urine concentration test

定义

A urine concentration test measures the ability of the kidneys to conserve or excrete water.

选择的名字

水装 test; 水不足 test

How the Test is Performed

对于这个测试， specific gravity of urine, 尿电解质和/或 尿液同渗重摩 are measured before and after one or more of the following:

• 水装. Drinking large amounts of water or receiving fluids through a vein.
• 水不足. Not drinking fluids for a certain amount of time.
• 抗利尿激素管理. Receiving antidiuretic hormone (ADH), which should cause the urine to become concentrated.

After you provide a urine sample, it is tested right away. For urine specific gravity, the health care provider uses a dipstick made with a color-sensitive pad. The dipstick color changes and tells the provider the specific gravity of your urine. The dipstick test gives only a rough result. For a more accurate specific gravity result or measurement of 尿电解质 or osmolality, your provider will send your urine sample to a lab.

If needed, your provider will ask you to collect your urine at home over 24 hours. Your provider will tell you how to do this. Follow instructions exactly.

How to Prepare for the Test

Eat your normal diet for several days before the test. Your provider will give you instructions for water loading or water deprivation.

Your provider will ask you to temporarily stop any medicines that may affect the test results. Be sure to tell your provider about all the medicines you take, including dextran and sucrose. DO NOT stop taking any medicine before talking to your provider.

Also tell your provider if you recently received intravenous dye (contrast medium) for an imaging test such as a CT or MRI scan. The dye can also affect test results.

考试的感觉如何

The test involves only normal urination. 没有不适.

Why the Test is Performed

This test is most often done if your doctor suspects central diabetes insipidus. The test can help tell that disease from nephrogenic diabetes insipidus.

This test may also be done if you have signs of syndrome of inappropriate ADH (SIADH).

正常的结果

In general, normal values for specific gravity are as follows:

• 1.005 to 1.030 (normal specific gravity)
• 1.001 after drinking excessive amounts of water
• 多于1.030 after avoiding fluids
• Concentrated after receiving ADH

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Increased urine concentration may be due to conditions, such as:

• Glucose (a type of sugar) in the urine
• 心脏衰竭
• Loss of body fluids (dehydration) from diarrhea or excessive sweating
• Narrowing of the kidney artery (renal arterial stenosis)
• Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
• 呕吐

Decreased urine concentration may indicate:

• 尿崩症
• 喝太多液体
• 肾功能衰竭 (loss of ability to reabsorb water)
• Severe kidney infection (pyelonephritis)

风险

There are no risks with this test.

参考文献

福加齐GB，加里加利G. 验尿. In: Feehally J, Floege J, Tonelli M, Johnson RJ, eds. Comprehensive Clinical Nephrology. 6日艾德. Philadelphia, PA: Elsevier; 2019:chap 4.

莱利RS，麦克弗森RA. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24日艾德. Philadelphia, PA: Elsevier; 2022:chap 29.