Alternative Names: Urinary chloride

How the test is performed:

A spot urinary chloride test or a 24-hour urine chloride sample may be needed.

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. A 24-hour urine test is performed as follows:

• On day 1, urinate into the toilet when you get up in the morning.
• Afterwards, collect all urine in a special container for the next 24 hours.
• On day 2, urinate into the container when you get up in the morning.
• Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

In infants, thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For boys, the entire penis can be placed in the bag and the adhesive attached to the skin. For girls, the bag is placed over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to prepare for the test:

No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel:

The test involves only normal urination, and there is no discomfort.

Why the test is performed:

Cl- is the major extracellular negative ion in the body. Its main purpose is to maintain electrical neutrality, mostly as a counter-ion to sodium. It often accompanies sodium losses and excesses. It also affects acid-base balance. That is, as CO2 (carbon dioxide) increases, bicarbonate moves from inside the cells to the outside. Then, to maintain electrical neutrality, more chloride tends to enter cells.

Because of its relationship with other electrolytes, urinary chloride results can be used to help assess volume status, salt intake, causes of hypokalemia, and to aid in the diagnosis of renal tubular acidosis.

Normal Values:

The normal range is 20 to 250 mEq/day. This range is highly dependent on salt intake and the state of the individual's hydration. Normal value ranges may vary slightly among different laboratories.

Note: mEq/day = milliequivalents per day

What abnormal results mean:

Increased urine chloride excretion may be caused by:

• Increased salt intake
• Postmenstrual diuresis
• Pharmacologic diuresis
• Salt-losing nephritis
• Adrenocortical insufficiency

Decreased urine chloride excretion may occur with:

• Decreased salt intake
• Adrenocortical hyperfunction
• Extrarenal fluid loss (such as diarrhea, vomiting, sweating, and gastric suction)
• Salt retention

What the risks are:

There are no risks.

Special considerations:

There are certain drugs that may interfere with this test. Drugs that may decrease urinary chloride excretion include acetazolamide and NSAIDs. Drugs that may increase urinary chloride excretion include: corticosteroids, loop diuretics, and thiazide diuretics.