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What is the importance of Urinalysis?
- 1. For hospital admissions and physical examinations.
- 2. One of the most useful indicators of health and disease.
- 3. Especially helpful in the detection of renal or metabolic disorders.
Parameters of Routine Urinalysis
- 1. Specimen Evaluation
- 2. Physical Examination
- 3. Chemical Examination
- 4. Microscopic Examination of the Urine Sediment
What is responsible for the amber yellow color of urine?
It is due largely to the pigment urochrome and to small amounts of urobilin and uroerythrin.
Cause and Remarks: Colorless Urine
- Cause: Very dilute urine
- Remarks: Polyuria, diabetes insipidus
Cause and Remarks: Cloudy urine
- Phosphates, carbonates - Soluble in dil. HAc
- Urates, uric acid - Dissolve at 60C and in alkali
- Leukocytes - Insoluble in dil. HAc
- Red cells (smoky) - Lyse in dil. HAc
- Bacteria, yeasts - Insoluble in dil. HAc
- Spermatozoa, prostatic fluid - Insoluble in dil. HAc
- Mucin, mucous threads - May be flocculent
- Calculi, gravel, clumps, pus, tissue - Phosphates, oxalates
- Fecal contamination - Rectovesical fistula
- Radiographic dye - In acid urine
Cause and Remarks: Milky urine
- Many neutrophils (pyuria) - Insoluble in dil. HAc
- Lipiduria (opalescent) - Nephrosis, crush injury - sol. in ether
- Chyluria (milky) - Lymphatic obstruction - sol. in ether
- Emulsified paraffin - Vaginal creams
Cause and Remarks: Yellow urine
- Cause: Acriflavine
- Remarks: Green fluorescence
Cause and Remarks: Yellow-Orange urine
- Concentrated urine - Dehydration, fever
- Urobilin in excess - No yellow foam
- Bilirubin - Yellow foam is sufficient bilirubin
Cause and Remarks: Yellow-Green urine
- Cause: Bilirubin-biliverdin
- Remarks: Yellow foam
Cause and Remarks: Yellow-Brown urine
- Cause: Bilirubin-biliverdin
- Remarks: "Beer" brown, yellow foam
Cause and Remarks: Red urine
- Hemoglobin - (+) rgt. strip for blood
- Erythrocytes - (+) rgt. strip for blood
- Myoglobin - (+) rgt. strip for blood
- Porphyrin - may be colorless
- Fuscin, aniline dye - Foods, candy
- Beets - Yellow alkaline, genetic
- Menstrual contamination - clots, mucus
Cause and Remarks: Red-Purple urine
- Cause: Porphyrins
- Remarks: may be colorless
Cause and Remarks: Red-Brown urine
- Hemoglobin on standing
- Methemoglobin - acid pH
- Myoglobin - Muscle injury
- Bilifuscin (dipyrrole) - Result of unstable hemoglobin
Cause and Remarks: Brown-Black urine
- Methemoglobin - Blood, acid pH
- Homogentisic acid - On standing, alkaline
- Melanin - alkaptonuria, on standing, rare, small intestine, infections
Cause and Remarks: Blue-Green urine
- Indicans - small intestine, infxns
- Pseudomonas infxns
- Chlorophyll - mouth deodorants
Function of the pH of urine
Reflection of the ability of the kidney to maintain normal hydrogen ion concentration in plasma and extracellular fluid.
2 Methods for measuring urine pH
1. Potentiometric method - accurate method but not practical for routine screening.
- 2. Indicator paper strips:
- a. litmus paper - much too crude for lab use
- b. nitrazine paper - range: pH 4.5 - 7.7
Function of sp. gravity, osmolality and refractive index
Test the kidney's function of maintaining fluid and osmolar balance.
Methods for measuring sp. gravity of Urine
1. hydrometer (urinometer)
Formula: Fahrenheit - Centigrade
C = 5/9 (F-32)
Formula: True specific gravity
True Sp. Gravity = [(Temp. of urine - temp. of calibration) / 3] * 0.001 + Sp. gravity reading
2 Qualitative Determination tests for Protein
- 1. Heat and Acetic acid
- 2. Bromphenol method (dipstick)
Principle of Heat and HAc for Protein
All methods for detection of protein, primarily albumin, depend on the precipitation of the protein by chemicals and heat. The degree of turbidity produced is proportional to the quantity of protein present. The coagulated protein is compared with untreated urine, and a rough estimate of the amount of protein is obtained. As the tests depend on the turbidity in the urine solution, URINE MUST BE CLEAR BEFORE USE.
Protein - Heat and HAc - Rgt. used
3 drops of 10% HAc (in 10 ml urine)
Protein - Heat & HAc - results
- Negative (no cloudiness)
- Trace (5-15 mg/dl)
- 1+ (25-50 mg/dl)
- 2+ (about 100 mg/dl)
- 3+ (about 200 - 300 mg/dl)
- 4+ (>500 mg/dl)
Principle of Bromphenol Method (dipstick) for Protein
This test is based on the phenomenon of "protein error of indicators" to produce a visible colorimetric reaction. At a fixed pH certain indicators will have one color in the presence of protein and another color in the absence of protein.
The citrate buffer protein provides a hydrogen ion concentration of approx. pH 3. At this pH, tetrabromphenol blue has a yellow color, whereas at the same pH in the presence of increasing amounts of protein, the indicator will have green to blue color.