PRESERVATION OF SPECIMENS
To delay decomposition, use
1. Refrigeration. All specimens not being ex-
amined immediately should be refrigerated.
2. Toluene. Simply add enough toluene to
form a thin film on the surface of the
specimen. This film will prevent air from
reaching the urine. False positives are
seldom encountered with this preservative.
Remember that the toluene is on the sur-
face, and all test samples must be pipetted
from BENEATH the surface.
3. Thymol. A small lump, floating on the sur-
face, will preserve a urine specimen for
several days. Enough thymol may dissolve
to produce false positives for albumin. Do
not use more that 0.1g of thymol per 100
ml of urine.
Other common preservatives are formalde-
hyde, boric acid, hydrochloric acid, and chloro-
form. The preservative used must be identified on
the label of the container. If no preservative is
used, it should be so stated.
Volume (For 24-Hour Specimen or When
The normal daily urine volume for adults
ranges from 800 to 2000 ml, averaging about 1,500
ml. The amount of urine excreted in 24 hours
varies with fluid intake and the amount of water
lost through perspiration, respiration, and bowel
activity. Diarrhia or profuse sweating will reduce
urinary output; a high protein diet tends to in-
crease it. Daytime urine output is normally two
to four times greater than nighttime output.
The normal color of urine varies from straw
to light amber. Diluted urines are generally pale;
concentrated urines tend to be darker. The terms
used to describe the color of urine are:
2. Light straw
4. Dark straw
5. Light amber
7. Dark amber
The color of urine may be changed by the
presence of blood, drugs, or diagnostic dyes. Ex-
1. Red or red-brown (smokey appearance),
due to the presence of blood.
2. Yellow or brown (turning greenish with
yellow foam when shaken), due to the
presence of bile.
3. Olive green to brown-black, caused by
4. Milky appearance, caused by chyle.
5. Dark orange,
due to treatment with
6. Blue-green, due to methylene blue.
Urine may be reported as clear, hazy, slightly
cloudy, cloudy, or very cloudy. Some physicians
prefer the term turbidity to transparency,
but both terms are acceptable.
Freshly passed urine is usually clear or
transparent. In certain conditions it may be cloudy
due to the presence of blood, phosphates, crystals,
pus, bacteria, etc. A report of transparency is of
value only if the specimen is fresh. After standing,
all urine becomes cloudy due to 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
and is of no significance.
Normal urine is slightly acid but will become
more alkaline upon standing. The pH ranges from
4.6 to 8.0. The acidity of urine is influenced by
many factors, such as a diet high in protein or
fat, fasting and starvation, and acid therapy.
Alkaline urine may be produced by cystitis,
pyelonephritis, and sulfonamide therapy.
It is essential that an alkaline urine be main-
tained during treatment with sulfonamides, since
these compounds are precipitated as crystals in
acid solution. The crystals will cause damage to
the uriniferous tubules. Sodium bicarbonate is
generally used as an alkalizer.
Reaction to pH, protein, glucose, ketones,
bilirubin, blood, nitrite, and urobilinogen in urine
may be determined by the use of the Multistix and