Physical Examination of Urine
All routine urinalysis should begin with a physical examination of the urine sample. This examination includes assessment of volume, odor, and appearance (color and turbidity).

Volume
Urinary volume is dependent upon fluid intake; amount of solutes to be excreted, primarily sodium and urea; loss of body fluids by normal processes, such as perspiration and respiration, and abnormal processes, such as diarrhea; and cardiovascular and renal function. Although the volume of a random specimen is clinically insignificant, the volume of specimen received should be recorded for purposes of ********ation and standardization.
Urine volumes can be measured two ways: volumetrically and gravimetrically. That is, the volume is measured with a volumetric cylinder, or the volume is estimated by weighing the urine sample in a tared container and assuming that 1g = 1mL of urine.

Odor
Non-pathological, fresh urine has an inoffensive odor. One usually determines the odor of the urine sample by placing ones nose near the orifice of the sample container , moving the air from the container to your nose by gently wafting with your hand, and gently breathing the fumes.

Appearance (color and turbidity)
Color—The color of urine is related, to a large degree, by its degree of concentration. The color of non-pathological urine varies widely from colorless to deep yellow; the more concentrated the urine, the deeper the color. The color of urine is usually described after visual inspection with common color terms. Very often color charts will be available to report the colors in a consistent fashion.
A good clinical history can resolve possible causes of an unusual urine color.

Turbidity—Normally freshly voided urine is clear. When urine is allowed to stand, amorphous crystals, usually urates, may precipitate and cause urine to be cloudy. The turbidity of urine should always be recorded and microscopically explained.
Specific gravity—A hydrometer (urinometer) and a suitable container may be used to determine specific gravity.


Many laboratories may also be equipped with refractometers that can relate density of a solution to specific gravity. Refractometers work on the principle that light passing from a transparent medium of one density to a medium of another density, will change its velocity and therefore the direction in which the beam of light is moving.


This change in direction, or the bending, of light is called refraction. The refractivity of a solution is dependent, in great part, on the total mass of solids dissolved in that solution. The refractive index scale can be calibrated to measure the specific gravity of most urine sample, that is up to 1.036 g/mL .

An indirect colorimetric method for estimating specific gravity is available on reagent strips ("urine dipsticks"). This method uses a pad that contains a complex, pre-treated electrolyte that undergoes a pH change based on the ionic concentration of the urine. This change results in a change of color of the pad. For the Multistix SG-10, specific gravity is measured using an apparent pKachange in the presence of an indicator (dyes) whose colors vary from deep blue-green at low ionic strength to green and yellow-green at higher ionic concentration. This estimate of specific gravity is rapid, simple, and requires no special equipment.
The falling drop method is a direct method of measuring specific gravity that is usually used with automated instruments, such as the Clinitek Auto 2000 (Ames Division, Miles Laboratories, Inc., Elkhart , IN). The CliniTek2000 uses a specially designed column containing silicone oil. Specific gravity is calculated from the time it takes for a drop of urine to fall between two optical gates.
Osmolality—Osmolality is usually measured by an osmometer, most frequently by a freezing point osmometer. Osmolalityis a measure of the number of particles per unit mass, whereas the specific gravity is a reflection of the density (mass per unit volume) of the suspended particles.
Clinical Significance—Primary kidney function includes the ability to produce, in the appropriate circumstances, either a concentrated urine (osmolality>850 mOsm/kg) or a dilute urine (osmolality<100 mOsm/kg). A random urine whose osmolality>600 mOsm/kg is presumptive evidence of an ability to concentrate urine. The urine osmolality thus is part of the mechanism of maintaining water balance. In the presence of excess free water, the kidneys will produce a dilute urine, while in periods of water lack, a concentrated urine is produced.
Loss of concentrating ability is often one of the earliest signs of kidney disease, clinically evidenced as nocturia (needing to void at night) and polyuria (increased volume of [usually dilute] urine).


Activity 1.1
Physical Examination of Urine
Instructions
1. Practice the procedure(s) for performing a physical examination of urine, specific gravity by refractometer and specific gravity by urinometer following the step-by-step procedure and using the worksheet(s).
2. Demonstrate your understanding of this lesson by:
o Completing a written examination successfully,
o Performing the procedure(s) for the physical examination of urine, specific gravity by refractometer, and specific gravity by urinometer satisfactorily for the instructor. All steps must be completed as listed.
Note: Consult manufacturers' directions or textbook reference before using instruments or performing tests.
Materials and Equipment
• Gloves
• Hand disinfectant
• Puncture-proof container for sharps
• Clear plastic conical centrifuge tubes
• Test tube rack
• Fresh urine sample
• Dropping pipet
• Refractometer or urinometer
• Distilled water
• Urinalysis report form or worksheet
• Soft tissue or soft paper towels
• Biohazard container
• 10% chlorine bleach solution or other surface disinfectant
• Urine control solutions


Procedure
Record in the comment section any problems encountered while practicing the procedure (or have a fellow student or the instructor evaluate your performance).
1. Wash hands and put on gloves.
2. Assemble equipment and materials.
3. Obtain a fresh urine specimen. If specimen has been refrigerated, allow it to reach room temperature before proceeding with tests.
4. Record the specimen identification on the worksheet (or report form).
5. Mix the urine gently by swirling and pour approximately 10 mL into a clear, conical centrifuge tube.
6. Observe the color of the urine (straw, yellow, red, etc.) and record on the worksheet.
7. Notice the odor of the urine. If unusual, record in "odor" comment section.
8. Observe and record the appearance or transparency of the urine (clear, slightly cloudy, turbid).
9. Measure the specific gravity using both the refractometer and urinometer (see procedures).
10. Discard urine sample properly.
11. Disinfect and clean equipment and return to proper storage.
12. Clean work area with disinfectant.
13. Remove and discard gloves appropriately.
14. Wash hands with hand disinfectant.


Activity 1.2
Measuring Specific Gravity: The Urinometer Method
Materials and Equipment
• Gloves
• Hand disinfectant
• Puncture-proof container for sharps
• Clear plastic conical centrifuge tubes
• Test tube rack
• Fresh urine sample
• Dropping pipet
• Urinometer
• Distilled water
• Urinalysis report form or worksheet
• Soft tissue or soft paper towels
• Biohazard container
• 10% chlorine bleach solution or other surface disinfectant
• Urine control solutions


Procedure
1. Pour 40-50 mL of distilled water into the glass cylinder (approximately three-fourths full).
2. Insert urinometer gently, with spinning motion.
3. Read the specific gravity from the scale on the stem of the urinometer as it stops spinning and record. (Specific gravity of water should be 1.000.)
4. Rinse equipment and dry with laboratory tissue and repeat steps with urine specimen and or QC controls, recording result(s).
5. Discard urine sample properly.
6. Disinfect and clean equipment and return to proper storage.
7. Clean work area with disinfectant.
8. Remove and discard gloves appropriately.
9. Wash hands with hand disinfectant.


Activity 1.3
Measuring Specific Gravity: The Refractometer Method
Materials and Equipment
• Gloves
• Hand disinfectant
• Puncture-proof container for sharps
• Clear plastic conical centrifuge tubes
• Test tube rack
• Fresh urine sample
• Dropping pipet
• Refractometer
• Distilled water
• Urinalysis report form or worksheet
• Soft tissue or soft paper towels
• Biohazard container
• 10% chlorine bleach solution or other surface disinfectant
• Urine control solutions


Procedure
1. Wash hands and put on gloves.
2. Assemble equipment and materials.
3. Obtain a fresh urine specimen. If specimen has been refrigerated, allow it to reach room temperature before proceeding with tests.
4. Record the specimen identification on the worksheet (or report form).
5. Mix the urine gently by swirling and pour approximately 10 mL into a clear, conical centrifuge tube.
6. Place one drop of distilled water on the glass plate of the refractometer and close gently.
7. Look through ocular and read the specific gravity from the scale. For water, the specific gravity should read 1.000. (If it does not, calibrate with the screwdriver provided with the refractometer).
8. Wipe the water from the glass plate, place one drop of urine control solution on the plate and close gently.
9. Look through the ocular, read the specific gravity from the scale, and record the control value.
10. Clean the glass plate with disinfectant and dry with a soft tissue.
11. Repeat steps 8-9 with a urine specimen(s), recording result(s).
12. Discard urine sample(s) properly.
13. Disinfect and clean equipment and return to proper storage.
14. Clean work area with disinfectant.
15. Remove and discard gloves appropriately.
16. Wash hands with hand disinfectant.