Phosphorus P (24 hour urine)

Phosphorus (P) The second most common mineral in the human body after calcium. It represents 1% of body weight, which means that the adult human body has about 600-700 g of phosphorus. The largest amounts of phosphorus are found in skeletal bone (85% in the form of hydroxyapatite), the rest in the muscles, nerves and blood.

Phosphorus plays an extremely important role in bone formation as well as in maintaining skeletal strength. It is also important for maintaining water-electrolyte balance in the body.

Its absorption takes place through the intestinal epithelium and its homeostasis depends on the kidneys, therefore, changes in phosphate levels are most often caused by impaired renal function.

The kidneys filter excess phosphate from the blood and excrete it in the urine. Consequently, in case of renal pathology, a large amount of phosphate accumulates in the urine.

When to take a phosphorus test?

Determination of urinary phosphorus is recommended to assess renal function, phospho-calcium balance, and nephrolithiasis.

How to prepare for the test?

Patient training is not required.

Study material / urine collection rule

24-hour urine. At 7 o'clock in the morning the patient urinates and does not store this urine, and during the next urination he collects the whole volume of urine in a plastic container (2-3 liter urine container) until 7 o'clock in the morning of the next day (24 hours); The patient should transfer 100 ml of urine from this container (e.g. with a syringe) to a disposable plastic cup for urine and should be stored at 2-8 ° C before the test (1-1,5 h).

Possible interpretation of the results

Concentration of phosphorus in urine increases:

• Primary hyperparathyroidism;
• Vitamin D deficiency;
• Renal tubular acidosis;
• Use of diuretics.

Concentration of phosphorus in urine decreases:

• Hypoparathyroidism;
• Pseudohypoparathyroidism;
• Vitamin D poisoning.

A diet rich in potassium reduces the excretion of phosphates by the kidneys, leading to hyperphosphatemia.

Resources

https://www.synevo.ro/shop/fosfor-urinar/
https://www.webmd.com/kidney-stones/urine-phosphate-test