Urine examinations in patients, Study notes of Biochemistry

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STUDY OF NORMAL

CONSTITUENTS OF URINE

By Sandipkumar Kanazariya

Physical Characteristics

Features Characteristic Reason

Volume 800-2500 ml/day Average 1500 ml /day

Quantity of Fluid & Food intake, Climate Change, Physical Exercise Appearance Fresh Sample - Clear & Transparent

On standing, Urine appears Turbid. Bacterial Action converts urine Urea to Ammonia. This makes urine Alkaline leading to precipitation of Phosphate, Oxalates and Urates. Color Fresh Sample – Straw / Amber color

Presence of Pigment Urochrom imparts color to the urine. Odor Aromatic Odor Presence of Volatile Organic Acids. On standing, urine gives ammonical smell due to conversion of urine Urea in Ammonia by Bacterial Action. pH Range : (4.8 – 7.5) Average 6.0 (Acidic)

Protein Diet makes more Acidic Urine. Diet Rich in fruits and vegetables makes Alkaline Urine. On standing Urine becomes Alkaline due to Ammonia Formation. Specific Gravity

1.012 – 1.024 Fluid Intake and Specific Gravity has Reciprocal Relationship.

• Now, Calibrated specific gravity at 20 oC =
• i. For every 3 oC rise in temperature add 0. as a correction factor from observed specific gravity.
• ii. For every 3 oC fall in temperature subtract 0.001 as a correction factor from observed specific gravity.

• Calibrated temperature= 20 oC for every 3 oC rise in temperature, correction factor =0.
• Room temperature=32 oC for 12 oC correction factor = 0.001 x 4 = 0.
• Rise temperature=12 oC
• Corrected or true specific gravity at 32 oC = Observed specific gravity + Correction Factor = 1.010 + 0.004 = 1.

Chemical composition

• Normal urine contains both organic & inorganic constituents.
• Inorganic constituent includes Na+, Cl-, K+, Ca++ , Mg, SO4-, NH 3 & traces of bicarbonate ions.
• Organic constituent includes urea, uric acid, creatinine, urobilinogen, hippuric acid, indican, ethereal sulphate etc.

TESTS OF ORGANIC

CONSTITUENTS

1. Sodium Hypobromide Test

Test Observation Inference

To 2 ml of urea solution in a test tube, add 5 drops of 40% sodium hydroxide + 8- 10 drops of bromine water.

Brisk effervescence of Nitrogen gas is observed

Urea is Confirmed. Normal Urine Contains Urea.

2. Specific Urease Test

• When urea is treated with the enzyme urease, it is converted to ammonia and corbonic acid. Under the pH of the reaction conditions, they are converted to ammonium carbonate.
• The pH of the solution goes above 8.5 when urea is converted to ammonium carbonate. At this pH, phenolphthalein gives pink colour.

B. Test for uric acid

• Uric acid is a reducing agent in alkaline condition. it reduces phosphotungstic acid to tungsten blue.

3. Benedict’s Uric Acid Reagent Test/

Phosphotungstic acid reduction test

Test Observation Inference

To 2 ml of uric acid solution, add 5 drops of Benedict’s uric acid reagent, followed by 5 drops of 20% Na2CO3.

Blue colour is obtained

Uric acid is confirmed. Normal urine contains uric acid.

4. Jaffe’s Test

Test Observation Inference

To 2ml Creatinine solution + 2 ml saturated picric acid solution + 1 ml of 10% NaOH.

Orange colour is obtained

Creatinine is Confirmed. Normal Urine Contains Creatinine.

INORGANIC

CONSTITUENTS