Urine 24 hours Urea, Urine Urea Nitrogen/24 Hours

Sample

1. The test sample is urine.
2. Collected urine for 24 hours.
3. The urine sample is stable at 4 to 8 °C for 4 days or preserves with thymol to avoid bacterial action.
   1. Discard the first urine sample and note the time. Add the last sample of urine to the container.
   2. 10 grams of boric acid can be used as preservative/24 hours.

Indications

1. This test is mainly used to:
   1. Determine protein metabolism.
   2. It determines the amount of protein needed by severely ill patients.
   3. It gives information about kidney function.
   4. It can monitor kidney disease.
   5. Patients with confirmed or suspected protein digestion and absorption problems.
   6. Patients on long-term enteral nutrition or parenteral nutrition.

Pathophysiology

1. Urea formula =     
2. Urea is the major excretory product of protein metabolism.

3. Urea is a low molecular weight substance and is easily excreted by glomeruli and is mostly excreted in the urine.
4. The kidneys excrete urea, so the excretion of urea can reflect kidney function.
   1. It is synthesized in the liver, carried to the kidney, filtered through the glomeruli, mostly into the urine.

5. 40% is reabsorbed by passive diffusion.
6. The rate of absorption depends upon:
   1. Urine flow rate.
   2. The degree of hydration.
7. 10 % of urea is excreted through:
   1. GI tract.
   2. Skin.
8. Blood urea level depends upon:
   1. Renal function and perfusion.
   2. The protein content of the diet.
   3. Amount of protein catabolism.

Normal

Source 1

Urine urea nitrogen

• 12 to 20 g/day (428.4 to 714 mmol/day).

Another source

• 6 to 7 G /24 hours ( 60 to 90 mg/dL )
• Another reference says:
  • 7 to 20 g /total volume
  • 12 to 24 g /24 hours.
• This also depends upon the protein intake.

The decreased urine urea level is seen in:

1. Malnutrition.
2. Too little amount of protein in the diet.
3. Kidney dysfunction.
4. Increased reabsorption.

The increased level is seen in:

1. Excessive protein intake.
2. Increased protein catabolism.
   

   Normal urine picture:

   Physical features	Chemical features	Microscopic findings
   Color = Pale yellow or amber Appearance = Clear to slightly hazy pH = 4.5 to 8.0 Specific gravity = 1.015 to 1.025	Blood = Negative Glucose = Negative Ketones= Negative Protein = Negative Bilirubin = Negative Urobilinogen = Negative (±) Leucocyte esterase = Negative Nitrite for bacteria = Negative	RBCs = Rare or Negative WBC = Rare or Negative Epithelial cells = Few Cast = Negative (Occasional hyaline) Crystal = Negative (Depends upon the pH of the urine) Bacteria = Negative

    

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