24 Hour Urine Phosphorus
- evaluation of endocrine disorders
- evaluation of kidney disease
- evaluation of kidney stones
- 900-1300 mg/24 hours
- Over a wide range of dietary intakes, roughly two thirds of ingested phosphorus is absorbed into the bloodstream. The maintenance of the phosphorus balance is achieved largely through renal exceretion. Proximal tubular reabsorption of inorganic phosphate is normally about 90% of the filtered load. Parathyroid hormone depresses the renal tubular reabsorption of inorganic phosphate.
- In the ACA method, inorganic phosphate combines with molybdate (MoO4) in acid solution to form a complex which is reduced by p- methylaminophenol sulfate ( PAMPS) & bisulfite. The 340 nm absorbance of the reduced phosphomolybdate solution is proportional to the inorganic phosphorus concentration & is measured using a two-filter (340-383 nm) end-point technique.
- Most of the phosphorus absorbed from the intestines of adults who are in phosphorus balance is excreted in the urine. About 90% of plasma phosphorus is filterable by the glomeruli. Ordinarily about 85% to 95% of the filtered phosphate is reabsorbed. Parathyroid hormone inhibits renal tubular reabsorption of phosphate. Whether phosphate is secreted by the renal tubules is uncertain.
- In chronic renal failure there is impaired excretion of phosphate, and progressive hyperphosphatemia occurs. This results in a fall in the plasma calcium concentration ( hypocalcemia), giving rise to secondary hyperparathyroidism. The elevated parathyroid hormone level causes calcium resorption from bones & normocalcemia or hypercalcemia may result.
- vitamin D-resistant rickets
- vitamin D toxicity
- renal tubular damage
- 2 mL aliquot of a 24-hour urine collection. Proper 24 hour urine collection procedure should be followed, & collection container should be refrigerated at 2-6 C during collection. Upon receipt in the work area, it should be well-mixed & measured in a graduated cylinder. The total volume should be recorded.
More General Terms
- Kaplan, Lawrence A. & Pesce, Amadeo J., Clinical Chemistry: Theory, Analysis, & Correlation, 2nd Edition, The C.V. Mosby Company, St. Louis, MO, 1989, pp. 357, 881-883.
- Henry, John Bernard, M.D., Clinical Diagnosis & Management by Laboratory Methods, 18th Edition, W.B. Saunders Company, Philadelphia, PA, 1991, pp. 154.
- ACA IV Discrete Clinical Chemistry Analyzer Instrument Manual, Volume 3A, Chapter 6: Test Methodology, PHOS 32.
- Clinical Guide to Laboratory Tests, 4th edition, HB Wu ed, WB Saunders, Philadelphia, 2006
- WebMD: Phosphate in Urine 
- Panel of 8 tests Laboratory Test Directory ARUP: 
- Panel of 29 tests Laboratory Test Directory ARUP: 
24 hour urine phosphorus (inorganic phosphate)