Urine sodium measurement assesses acid-base balance, water balance, water poisoning, and dehydration.
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Sodium (Na) has the highest concentration of electrolytes measured in the blood. It is the principal cation in extracellular fluid. Sodium plays a vital role in acid-base balance and neuromuscular function. It maintains an inverse relationship with blood potassium levels. Usually, the body uses what is needed from sodium intake in the diet, and the excess is excreted in the urine. Several mechanisms regulate this balance. Any problem with any of the regulatory mechanisms can cause abnormal sodium levels in the blood. These mechanisms include the production of hormones that increase (natriuretic peptide) or decrease (aldosterone), the elimination of sodium in the urine, and the production of antidiuretic hormone (ADH) that prevents water loss. Another mechanism is thirst. When sodium levels rise in the blood, thirst is created, and the resulting water intake helps to return Sodium to blood levels.
The sodium concentration in the blood is closely related to the balance of body fluids. Its concentration stimulates the kidneys to compensate for changes in body fluid balance. For example, as the body's water increases, the sodium concentration decreases. This stimulates the kidneys to compensate through sodium retention and water excretion, which is accomplished through the action of aldosterone. If the body's water decreases, the blood's sodium concentration increases. This activates the secretion of the antidiuretic hormone, resulting in water retention.
Blood sodium is measured when the patient has symptoms of sodium imbalance or disorders associated with abnormal sodium levels. Hyponatremia is a state of reduced sodium levels in the blood. Signs of this imbalance include lethargy, confusion, abdominal cramps, anxiety, oliguria, rapid and weak pulse, headache, reduced skin tenderness, tremors, convulsions, and possibly coma. Hypernatraemia is a condition in which blood sodium levels are above normal. Signs of this imbalance include dry mucous membranes, fever, thirst, and anxiety.
Measuring sodium levels in a 24-hour urine collection is also crucial in determining the cause of abnormal blood sodium levels. It is also helpful in assessing adherence to patients with a low-sodium diet. Determining the sodium level in the urine helps in the differential diagnosis of conditions with low sodium concentration in the blood. If the cause of this abnormality is due to insufficient sodium intake, urine sodium levels will also be low. However, if the cause is due to kidney dysfunction, such as chronic kidney failure, the urine sodium level will be high.
Possible Interpretations of Pathological Values
- Increase: Hyponatremia as a result of renal salt loss, osmotic diuresis, renal failure with water retention, dehydration, fever, head trauma, hypernatremia, hyponatremia, kidney stone, nephrotic syndrome, salicylate toxicity, fasting, syndrome of inappropriate antidiuretic hormone secretion. Medications: Caffeine, calcitonin, cisplatin, diuretics, dopamine, heparin, lithium, niacin, sulfates, tetracycline, vincristine
- Decrease: Hyponatraemia associated with edema or tumor reduction due to extrinsic causes, acute renal failure, diarrhea, emphysema, fluid retention, malabsorption, pyloric obstruction, and celiac disease. Medications: Corticosteroids, diazoxide, epinephrine, propranolol
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. Between 70 to 80% of diagnostic decisions are based on laboratory tests. Correctly interpreting laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
