LEARNING OBJECTIVE: Recall the three types of urine specimens, the methods used to preserve urine specimens, and the procedure for performing a urinalysis.

Since the physical and chemical properties of normal urine are constant, abnormalities are easily detected. The use of simple tests provides the physician with helpful information for the diagnosis and management of many diseases. This section deals with the three types of urine specimens, methods used to preserve urine specimens, the procedure for performing a routine and microscopic examination of urine specimens, and some of the simpler interpretations of the findings.

URINE SPECIMENS
Urine specimens for routine examinations must be collected in aseptically clean containers. Unless circumstances warrant, avoid catheterization because it may cause a urinary tract infection. Specimens of female patients are likely to be contaminated with albumin and blood from menstrual discharge, or with albumin and pus from vaginal discharge. For bacteriologic studies, care must be taken to ensure that the external genitalia have been thoroughly cleansed with soap and water. The patient must void the initial stream of urine into the toilet or a suitable container and the remainder directly into a sterile container. All urine specimens should either be examined when freshly voided, or refrigerated to prevent decom- position of urinary constituents and to limit bacterial growth. In the following sections, we will cover three types of urine specimens: random, first morning, and 24-hour.

Random Urine Specimen
A random urine specimen is urine voided without regard to the time of day or fasting state. This sample is satisfactory for most routine urinalyses. It is the least valid specimen, since test results may reflect a particular meal or fluid intake.

First Morning Urine Specimen
The first morning urine specimen is the first urine voided upon rising. It is the best sample for routine urinalysis, because it is usually concentrated and more likely to reveal abnormalities. If positive results are obtained from the first morning specimen, the physician may order a 24-hour specimen for quantitative studies.

Twenty-Four Hour Urine Specimen
The 24-hour urine specimen measures the exact output of urine over a 24-hour period. Use the following steps to collect this specimen.

1. Have patient empty bladder early in the morning and record time. Discard this urine.

2. Collect all urine voided during next 24 hours.
3. Instruct patient to empty bladder at 0800 the following day (end of 24-hour period). Add this urine to pooled specimen.

Refrigerate specimen during collection, and, depending on the test being performed, add a preservative to the first specimen voided.

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. Diarrhea or profuse sweating reduces urinary output; a high-protein diet tends to increase it. Daytime urine output is normally two to four times greater than nighttime output.

PRESERVATION OF URINE SPECIMENS
To delay decomposition of urine, use the following methods of preservation:

Refrigeration
Preservatives
-Hydrochloric acid
-Boric acid
-Glacial acetic acid
Other preservatives used include formaldehyde, toluene, and thymol. The preservative used must be identified on the label of the container. If no preservative is used, this, too, should be noted.

NOTE: Before adding a preservative to a urine specimen, contact the laboratory performing the test to find out what preservative to use and the quantity to add. Preservative requirements vary from laboratory to laboratory.

ROUTINE URINE EXAMINATION
A routine urinalysis includes the examination of physical characteristics, chemical characteristics, and microscopic structures in the sediment. A sample for urinalysis (routine and microscopic) should be at least 15 ml in volume (adult), and either a random or first morning specimen. Children may only be able to provide a small volume, but 10-15 ml is preferred.