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Physical Characteristics
Physical characteristics evaluated during a routine urinalysis include color, appearance, and specific gravity.

COLOR.-The normal color of urine varies from straw to light amber. Diluted urine is generally pale; concentrated urine tends to be darker. The terms used to describe the color of urine follow.

Light straw
Dark straw

Light amber
Dark amber
The color of urine may be changed by the presence of blood, drugs, or diagnostic dyes. Examples are:

red or red-brown (smokey appearance), caused by the presence of blood.

yellow or brown (turning greenish with yellow foam when shaken), caused by the presence of bile.
olive green to brown-black, caused by phenols (an extremely poisonous compound, used as an antimicrobial agent).
milky white, caused by chyle. (Chyle, which consists of lymph and droplets of triglyceride, is a milky fluid taken up by lacteal vessels from the food in the intestine during digestion.)

* dark orange, caused by Pyridium(r) (a topical analgesic used in the treatment of urinary tract infections).
blue-green, caused by methylene blue (used as a stain or dye for various diagnostic tests).

APPEARANCE.-Urine's appearance may be reported as clear, hazy, slightly cloudy, cloudy, or very cloudy. Some physicians prefer the term "turbidity" instead of "transparency," but both terms are acceptable.

Freshly passed urine is usually clear or transparent. However, urine can appear cloudy when substances such as blood, phosphates, crystals, pus, or bacteria are present. A report of transparency is of value only if the specimen is fresh. After standing, all urine becomes cloudy because of decomposition, salts, and the action of bacteria. Upon standing and cooling, all urine specimens will develop a faint cloud composed of mucus, leukocytes, and epithelial cells. This cloud settles to the bottom of the specimen container and is of no significance.

SPECIFIC GRAVITY.-The specific gravity of the specimen is the weight of the specimen compared to an equal volume of distilled water. The specific gravity varies directly with the amount of solids dissolved in the urine and normally ranges from 1.015 to 1.030 during a 24-hour period.

The first morning specimen of urine is more concentrated and will have a higher specific gravity than a specimen passed during the day. A high fluid intake may reduce the specific gravity to below 1.010. In the presence of disease, the specific gravity of a 24-hour specimen may vary from 1.001 to 1.060.

Specific gravity is measured with an index refractometer, available as standard equipment at most duty stations. See figure 7-22. The index refracto- meter may be held manually or mounted on a stand like a microscope. The specific gravity of urine is determined by the index of light refraction through solid material.

Measure the specific gravity with an index refractometer in the following manner:

1. Hold the index refractometer in one hand. Use the other hand and an applicator stick to place a drop of urine on the glass section beneath the coverglass.

2. Hold the refractometer so that the light reflects on the glass section, and look into the ocular end. Read the number that appears where the light and dark lines meet. This is the specific gravity.

Chemical Characteristics
Chemical characteristics evaluated during a routine urinalysis include pH, protein, glucose, ketones, and blood. Some laboratories also include tests for bilirubin, urobilinogen, and nitrite, depending on the test strip used. Currently, most medical facilities use the Multistix(r) and Color Chart, which detects pH, protein, glucose, ketones, blood, bilirubin, and urobilinogen. The Multistix is a specially prepared multitest strip. The strip is simply dipped into the urine specimen and compared to the color values for the various tests on the accompanying chart. The color chart also indicates numerical pH values, which should be reported.


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