Urine Potassium (K⁺)

Sample for Urine potassium (K⁺)

1. Collect 24 hours of urine.
2. Procedure to collect 24-hour urine: Discard the first sample and note the time.
3. Collect the rest of the urine for 24 hours and urinate the last sample into the container.
4. Refrigerate the urine during collection.

Indications for Urine potassium (K⁺)

1. This study is done on renal and adrenal disorders.
2. This is done for water and acid-base balance.
3. This is done in support of hypercalcemia.

Precautions for Urine potassium (K⁺)

1. Potassium in the diet will affect the urinary potassium level.
2. Drugs that increase the potassium level are diuretics, salicylates, and glucocorticoids.
3. Licorice increases potassium excretion in the urine.

Pathophysiology of Urine potassium (K⁺)

1. Potassium is the major cation within the cells (Intracellular).
   1. 98% of the potassium (K⁺) is found in the ICW (intracellular water) space.
   2. In the extracellular water space (ECW), the concentration of potassium is only 3.5 to 5 mmol/L.
   3. The concentration reaches about 150 to 160 mmol/L.
2. Total body potassium (K⁺) in an adult male is about 50 mmol/Kg of body weight.

3. Potassium concentration depends upon the following:
   1. Aldosterone.
   2. Glucocorticoids.

Kidneys’ role in Potassium (K⁺) regulation:

1. Kidneys are important for the regulation of the K⁺ level.
2. Kidneys can not reabsorb the potassium.
3. Intake of potassium is balanced by the kidneys by the excretion of potassium in the urine.
4. Proximal tubules reabsorb all the K⁺.
   1. Aldosterone additional K⁺ is excreted into the urine in exchange for Na⁺.
   2. The distal nephron is the main determinant of urinary K⁺ excretion.

5. Even if an excess of K⁺ is taken, this is still excreted in the urine except in patients with renal failure, where the K⁺ level may enter the toxic level. This is an active process that depends upon ATPase activity.

6. This is the amount of potassium excreted in the urine.

Potassium (K⁺) level in Alkalosis:

1. In the case of Alkalosis, there is increased secretion of Potassium in the urine.

Potassium (K+) in acidosis:

1. In the case of acidosis, there is decreased secretion of potassium in the urine.

Urine Potassoim (K⁺)  important facts:

1. Urine potassium (K⁺) concentration is important in the differential diagnosis of hypokalemia.
   1. Urine potassium (K⁺)  concentration <20 mmol/L with hypokalemia is suggestive of inadequate intake of potassium (K⁺)  or nonurinary loss.
   2. While urine potassium (K⁺) level of >20 mmol/L is consistent with urinary loss.
2. Urine K⁺ >30 meq/day is inappropriate in hypokalemic patients and strongly suggests a hyperaldosteronism state.
   1. Spot urine test K⁺ > Na⁺ is also suggestive.
3. Urine K⁺ <30 meq/day reflects renal  K⁺ retention as seen in diuretic use or gastrointestinal loss.
4. Urine potassium (K⁺) has little value in the differential diagnosis of hyperkalemia.

Causes of Potassium (K+) depletion:

1. Potassium (K⁺) depletion occurs when the potassium (K⁺) output exceeds intake.
2. A small amount of potassium (K⁺) is lost in the stool in normal conditions.

Causes of potassium (K⁺) retention in the body:

1. Potassium (K⁺) accumulates in the body when the intake of potassium (K+) increases the output because of some abnormality in the potassium (K⁺) homeostasis.
2. Under normal conditions, kidneys can compensate for the imbalance.
3. High potassium (K⁺) intake leads to potassium retention only when the kidney’s functions are disturbed.

NORMAL  Urine Potassium (K⁺)

Source 1

• Values vary with diet.

Source 2

• 25 to 100 meq / L / day (25 to 100 mmol/day).
  • Values vary with diet.

Increased urine Potassium (K+) level is seen in the:

1. Diuretic therapy.
2. Cortisone therapy.
3. Drugs like penicillin and carbenicillin
4. Thiazides.
5. Chronic renal failure.
6. Starvation.
7. Hyperaldosteronism.
8. Renal tubular acidosis.
9. Cushing’s syndrome.
10. Alkalosis.
11. Excessive intake of licorice.

Decreased Urine Potassium (K⁺) level is seen in:

1. Diazoxide.
2. Amiloride.
3. I/V glucose infusion.
4. Dehydration.
5. Malnutrition.
6. Diarrhea.
7. Vomiting.
8. Malabsorption.
9. Addison disease.
10. Acute renal failure where urinary K will be low, but the patient will have hyperkalemia.

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