Sodium, Urine

Synonym/acronym: Urine Na⁺.

Common use

To assist in evaluating for acute renal failure, acute oliguria, and to assist in the differential diagnosis of hyponatremia.

Specimen

Urine (5 mL) from an unpreserved random or timed specimen collected in a clean plastic collection container.

Normal findings

(Method: Ion-selective electrode)

Age	Conventional Units	SI Units (Conventional Units × 1)
6–10 yr
Male	41–115 mEq/24 hr or mmol/24 hr	41–115 mmol/24 hr
Female	20–69 mEq/24 hr or mmol/24 hr	20–69 mmol/24 hr
10–14 yr
Male	63–177 mEq/24 hr or mmol/24 hr	63–177 mmol/24 hr
Female	48–168 mEq/24 hr or mmol/24 hr	48–168 mmol/24 hr
Adult–older adult	27–287 mEq/24 hr or mmol/24 hr	27–287 mmol/24 hr

Values vary markedly depending on dietary intake and hydration state.

Description

Sodium balance is dependent on a number of influences in addition to dietary intake, including aldosterone, renin, and atrial natriuretic hormone levels. Regulating electrolyte balance is a major function of the kidneys. In normally functioning kidneys, urine sodium levels increase when serum levels are high and decrease when serum levels are low to maintain homeostasis. Analyzing these urinary levels can provide important clues to the functioning of the kidneys and other major organs. There is diurnal variation in excretion of sodium, with values lower at night. Urine sodium tests usually involve timed urine collections over a 12- or 24-hr period. Measurement of random specimens may also be requested.

This procedure is contraindicated for

N/A

Indications

Determine potential cause of renal calculi
Evaluate known or suspected endocrine disorder
Evaluate known or suspected renal disease
Evaluate malabsorption disorders

Potential diagnosis

Increased in

Adrenal failure (inadequate production of aldosterone results in decreased renal sodium absorption)
Dehydration (related to decreased water excretion, which results in higher concentration of the urine constituents)
Diabetes (increased glucose levels result in hypertonic extracellular fluid; dehydration from excessive urination can cause hemoconcentration)
Diuretic therapy (medication causes sodium to be lost by the kidneys)
Excessive intake
Renal tubular acidosis (related to diabetes)
Salt-losing nephritis (related to diminished capacity of the kidneys to reabsorb sodium)
Syndrome of inappropriate antidiuretic hormone secretion (related to increased reabsorption of water by the kidneys, which results in higher concentration of the urine constituents)

Decreased in

(overproduction of aldosterone and other corticosteroids stimulate renal absorption of sodium decreasing urine sodium levels)

(decreased renal blood flow related to diminished cardiac output)

(related to decreased intestinal absorption; a decrease in blood levels will cause sodium to be retained by the kidneys and will lower urine sodium levels)

(excessive loss of sodium through sweat; sodium will be retained by the kidneys)

(premenstrual)

Critical findings

N/A

Interfering factors

Drugs that may increase urine sodium levels include acetazolamide, acetylsalicylic acid, amiloride, ammonium chloride, azosemide, benzthiazide, bumetanide, calcitonin, chlorothiazide, clopamide, cyclothiazide, diapamide, dopamine, ethacrynic acid, furosemide, hydrocortisone, hydroflumethiazide, isosorbide, levodopa, mercurial diuretics, methyclothiazide, metolazone, polythiazide, quinethazone, spironolactone, sulfates, tetracycline, thiazides, torasemide, triamterene, trichlormethiazide, triflocin, verapamil, and vincristine.
Drugs that may decrease urine sodium levels include aldosterone, anesthetics, angiotensin, corticosteroids, cortisone, etodolac, indomethacin, levarterenol, lithium, and propranolol.
Sodium levels are subject to diurnal variation (output being lowest at night), which is why 24-hr collections are recommended.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist in evaluating kidney function.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s endocrine and genitourinary systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
Review the procedure with the patient. Provide a nonmetallic urinal, bedpan, or toilet-mounted collection device. Address concerns about pain and explain that there should be no discomfort during the procedure.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Usually a 24-hr time frame for urine collection is ordered. Inform the patient that all urine must be saved during that 24-hr period. Instruct the patient not to void directly into the laboratory collection container. Instruct the patient to avoid defecating in the collection device and to keep toilet tissue out of the collection device to prevent contamination of the specimen. Place a sign in the bathroom to remind the patient to save all urine.
Instruct the patient to void all urine into the collection device and then to pour the urine into the laboratory collection container. Alternatively, the specimen can be left in the collection device for a health care staff member to add to the laboratory collection container.
Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

Potential complications: N/A
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection.

Random Specimen (Collect in Early Morning)

Clean-Catch Specimen
Instruct the male patient to (1) thoroughly wash his hands, (2) cleanse the meatus, (3) void a small amount into the toilet, and (4) void directly into the specimen container.
Instruct the female patient to (1) thoroughly wash her hands; (2) cleanse the labia from front to back; (3) while keeping the labia separated, void a small amount into the toilet; and (4) without interrupting the urine stream, void directly into the specimen container.
Indwelling Catheter
Put on gloves. Empty drainage tube of urine. It may be necessary to clamp off the catheter for 15 to 30 min before specimen collection. Cleanse specimen port with antiseptic swab, and then aspirate 5 mL of urine with a 21- to 25-gauge needle and syringe. Transfer urine to a sterile container.
Timed Specimen
Obtain a clean 3 L urine specimen container, toilet-mounted collection device, and plastic bag (for transport of the specimen container). The specimen must be refrigerated or kept on ice throughout the entire collection period. If an indwelling urinary catheter is in place, the drainage bag must be kept on ice.
Begin the test between 6 and 8 a.m., if possible. Collect first voiding and discard. Record the time the specimen was discarded as the beginning of the timed collection period. The next morning, ask the patient to void at the same time the collection was started and add this last voiding to the container. Urinary output should be recorded throughout the collection time.
If an indwelling catheter is in place, replace the tubing and container system at the start of the collection time. Keep the container system on ice during the collection period, or empty the urine into a larger container periodically during the collection period; monitor to ensure continued drainage, and conclude the test the next morning at the same hour the collection was begun.
At the conclusion of the test, comparethe quantity of urine with the urinary output record for the collection; if the specimen contains less than what was recorded as output, some urine may have been discarded, invalidating the test.
Include on the collection container’s label the amount of urine, test start and stop times, and any foods or medications that can affect test results.
General
Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
Instruct the patient to resume usual diet, fluids, medications, and activity, as directed by the HCP.
Nutritional Considerations: If appropriate, educate patients with low sodium levels that the major source of dietary sodium is found in table salt. Many foods, such as milk and other dairy products, are also good sources of dietary sodium. Most other dietary sodium is available through the consumption of processed foods. Patients on low-sodium diets should be advised to avoid beverages such as colas, ginger ale, sports drinks, lemon-lime sodas, and root beer. Many over-the-counter medications, including antacids, laxatives, analgesics, sedatives, and antitussives, contain significant amounts of sodium. The best advice is to emphasize the importance of reading all food, beverage, and medicine labels.
Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include ACTH, aldosterone, anion gap, ANP, BNP, blood gases, BUN, calcium, calculus kidney stone panel, carbon dioxide, chloride, chloride sweat, cortisol, creatinine, DHEAS, echocardiography, glucose, insulin, ketones, lactic acid, lung perfusion scan, magnesium, osmolality, potassium, renin, sodium, and UA.
Refer to the Endocrine and Genitourinary system tables at the end of the book for related tests by body system.