Potassium, Urine

Synonym/acronym: Urine K⁺.

Common use

To evaluate electrolyte balance, acid-base balance, and hypokalemia.

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	17–54 mEq/24 hr or mmol/24 hr	17–54 mmol/24 hr
Female	8–37 mEq/24 hr or mmol/24 hr	8–37 mmol/24 hr
10–14 yr
Male	22–57 mEq/24 hr or mmol/24 hr	22–57 mmol/24 hr
Female	18–58 mEq/24 hr or mmol/24 hr	18–58 mmol/24 hr
Adult–older adult	26–123 mEq/24 hr or mmol/24 hr	26–123 mmol/24 hr

Note: Reference values depend on potassium intake and diurnal variation. Excretion is significantly higher at night.Potassium excretion declines in older adults due to the decline in aldosterone levels, decline in renal function, and effects of commonly prescribed medications that inhibit the renin-angiotensin-aldosterone system.

Description

Electrolytes dissociate into electrically charged ions when dissolved. Cations, including potassium, carry a positive charge. Body fluids contain approximately equal numbers of anions and cations, although the nature of the ions and their mobility differs between the intracellular and extracellular compartments. Both types of ions affect the electrical and osmolar functions of the body. Electrolyte quantities and the balance among them are controlled by oxygen and carbon dioxide exchange in the lungs; absorption, secretion, and excretion of many substances by the kidneys; and secretion of regulatory hormones by the endocrine glands. Potassium is the most abundant intracellular cation. It is essential for the transmission of electrical impulses in cardiac and skeletal muscle. It also functions in enzyme reactions that transform glucose into energy and amino acids into proteins. Potassium helps maintain acid-base equilibrium, and it has a significant and inverse relationship to pH: A decrease in pH of 0.1 increases the potassium level by 0.6 mEq/L.

Abnormal potassium levels can be caused by a number of contributing factors, which can be categorized as follows:

Altered renal excretion: Normally, 80% to 90% of the body’s potassium is filtered out through the kidneys each day (the remainder is excreted in sweat and stool); renal disease can result in abnormally high potassium levels.
Altered dietary intake: A severe potassium deficiency can be caused by an inadequate intake of dietary potassium.
Altered cellular metabolism: Damaged red blood cells (RBCs) release potassium into the circulating fluid, resulting in increased potassium levels.

Regulating electrolyte balance is one of the major functions of the kidneys. In normally functioning kidneys, urine potassium levels increase when serum levels are high and decrease when serum levels are low to maintain homeostasis. The kidneys respond to alkalosis by excreting potassium to retain hydrogen ions and increase acidity. In acidosis, the body excretes hydrogen ions and retains potassium. Analyzing these urinary levels can provide important clues to the functioning of the kidneys and other major organs. Urine potassium tests usually involve timed urine collections over a 12- or 24-hr period. Measurement of random specimens also may be requested.

This procedure is contraindicated for

N/A

Indications

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

Potential diagnosis

Increased in

Albright-type renal disease (related to excessive production of cortisol)
Cushing’s syndrome (excessive corticosteroids, especially aldosterone levels, will increase urinary excretion of potassium)
Diabetic ketoacidosis (insulin deficiency forces potassium into the extracellular fluid; excess potassium is excreted in the urine)
Diuretic therapy (related to potassium-wasting effects of the medications)
Hyperaldosteronism (excessive aldosterone levels will increase urinary excretion of potassium)
Starvation (onset) (cells involved in providing energy through tissue breakdown release potassium into circulation)
Vomiting (elevated urine potassium is a hallmark of bulimia)

Decreased in

(reduced aldosterone levels will diminish excretion of potassium by the kidneys)

Critical findings

N/A

Interfering factors

Drugs and substances that can cause an increase in urine potassium levels include acetazolamide, acetylsalicylic acid, ammonium chloride, bendroflumethiazide, carbenoxolone, chlorthalidone, clopamide, corticosteroids, cortisone, diapamide, dichlorphenamide, diuretics, ethacrynic acid, fludrocortisone, furosemide, hydrochlorothiazide, hydrocortisone, intra-amniotic saline, mefruside, niacinamide, some oral contraceptives, thiazides, torsemide, triflocin, and viomycin.
Drugs that can cause a decrease in urine potassium levels include anesthetic agents, felodipine, and levarterenol.
A dietary deficiency or excess of potassium can lead to spurious results.
Diuretic therapy with excessive loss of electrolytes into the urine may falsely elevate results.
All urine voided for the timed collection period must be included in the collection, or else falsely decreased values may be obtained. Compare output records with volume collected to verify that all voids were included in the collection.
Potassium levels are subject to diurnal variation (output being highest 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 electrolyte balance.
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, gastrointestinal, 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 ingestion of 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.
Nutritional Considerations: Potassium is present in all plant and animal cells, making dietary replacement simple to achieve in the potassium-deficient patient.
Observe the patient for signs and symptoms of fluid volume excess related to excess potassium intake, fluid volume deficit related to active loss, or risk of injury related to an alteration in body chemistry. Symptoms include dehydration, diarrhea, vomiting, or prolonged anorexia. Instruct the patient in electrolyte replacement therapy and changes in dietary intake that affect electrolyte levels, as ordered.
Increased potassium levels may be associated with dehydration. Evaluate the patient for signs and symptoms of dehydration. Dehydration is a significant and common finding in geriatric patients and other patients in whom renal function has deteriorated.
Patients receiving digoxin or diuretics should have potassium levels monitored carefully because cardiac arrhythmias can occur.
Increased urine potassium levels may be associated with the formation of kidney stones. Educate the patient, if appropriate, on the importance of drinking a sufficient amount of water when kidney stones are suspected.
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, BUN, calcium, calculus kidney stone panel, carbon dioxide, chloride, cortisol, creatinine, DHEAS, glucose, insulin, ketones, lactic acid, magnesium, osmolality, phosphorus, potassium, renin, sodium, and UA.
Refer to the Endocrine, Gastrointestinal, and Genitourinary systems tables at the end of the book for related tests by body system.