Basic Routine Urinalysis and Its Role in the Diagnosis of Kidney Diseases

Specimen for urinalysis

1. The best specimen for routine urinalysis is the first, early morning urine.

2. The mid-stream urine should be collected in a clean, dry and sterile container or specimen bottle.

3. Contaminations with blood, stool, soil, water and other contaminants should be avoided.

4. The specimen should be tested within a period of an hour to ensure reliability of results.

5. If the specimen could not be tested immediately, it should be preserved at refrigerated temperatures. (2- 8 degrees centigrade ) A preservative could be added for other tests needing 24-hour urine samples. ( toluene)

Urinalysis procedure

There are three phases of urinalysis, the physical, chemical and the microscopic examinations.

Physical examination

1. Color - the color of the urine is noted. Normal color is from light yellow to amber.

2. Odor - normal odor of urine is aromatic.

3. Transparency - normal urine is clear. Non-pathologic turbidity can be seen in the presence of amorphous sediments.

4. Specific gravity - specific gravity differs according to the type of specimen. A 24-hr urine specimen has a higher specific gravity than a random urine sample, because of the higher concentration of urinary sediments present in the 24-hr urine sample.

Chemical examination

This can include several parameters, like bilirubin, nitrites, ketone bodies, urobilinogen, pH, blood and many more. The two most common parameters are protein (albumin) and sugar (glucose) which should be both negative.

A positive protein indicates a condition which could be pathologic, while a positive sugar can indicate diabetes mellitus.

Microscopic examination

1. The urine is mixed thoroughly.

2. It is then centrifuged at 2,500 rpm for 5- 10 minutes.

3. The supernatant fluid is discarded leaving a few drops at the bottom of the tube.

4. This is placed in a clean, dry glass slide and covered with a cover slip.

5. The slide is then examined under the microscope. Scan with the low power objective (LPO) and then focus suspicious looking sediments under the high
power objective (HPO).

6. The sediments seen are then reported according to standard reporting.

Routine urinalysis basically rules out upper and lower urinary tract infections. One negative sample should not be considered conclusive. Three early morning urine samples should be examined before a diagnosis could be made. Of course, the history of the patient, physical symptoms and other laboratory result should be taken into consideration. At times, an X-ray, IVP or blood test could be useful for a clinician or doctor to arrive at an accurate diagnosis.