To delay decomposition, use
1. Refrigeration. All specimens not being examined 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 surface, and all test samples must be pipetted from BENEATH the surface.
3. Thymol. A small lump, floating on the surface, 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 formaldehyde, boric acid, hydrochloric acid, and chloroform. The preservative used must be identified on the label of the container. If no preservative is used, it should be so stated.
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 increase 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. Examples are:
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 phenols.
4. Milky appearance, caused by chyle.
5. Dark orange, due to treatment with Pyridium.
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 maintained 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