Laboratory Tests of UrineNo patient health evaluation is complete without the findings of laboratory tests of blood and Urine.
The doctor or his assistant may give special instructions about food and water intake well in advance of the time for delivering a urine specimen because those factors can
influence the chemical makeup of the sample. The time of day of the
collection also can affect the composition of the urine sample ; urine voided early in the morning is likely to be more acid in content, while urine collected after a meal may be
more alkaline. Thus, for a routine physical, the doctor may advise that a urine sample be taken at his office inumber the morning. But that nothing be eaten since the previous evening meal.
The doctor also may want not the first, but the second specimen of the day. In some cases, depending upon the patient's complaint, the doctor may request a collection of all the urine voided during a period of 12 or 24 hours.
WHAT ARE THE CHEMICAL CONTENT OF A URINE ?A typical urine sample is, of course, mostly water. But it also may contain about two dozen identifiable minerals and other chemicals, including sodium, potassium, calcium, sulfur, ammonia, urea, and several different acids. A urine sample can range in color from pale straw to dark amber, depending upon the concentration,
It also can be other colors, including orange or blue, Or even colorless
depending upon foods eaten, medications taken, diseases, or exposure to toxic substances.
WHAT ARE THE APPEARANCE AND ACIDITY OF URINE ?The urine sample's general appearance,
including color, is noted by the laboratory technician. The sample also is tested for acidity or alkalinity, normal urine being just slightly on the acid side of neutral. Urine
that is definitely acidic can be a sign of a variety of disorders, including certain metabolic problems. Urine that is markedly on the alkaline side of neutral also can suggest a number of possible disorders, including an infection of the urinary tract.
Alkalinity could also be caused by certain
medications, or even by the parent's use of large doses of bicarbonate of soda. Foods rich in protein can make the urine more acidic, while citrus fruits and some vegetabies may tend to make a patient's
urine more alkaline.
WHAT THE URINE SHOWS ?
A thorough analysis of a person's urine
can turn up some clues to the condition
of almost every part of the body and verify or rule out the presence of myriad physical disorders. The specific gravity of the urine, for example, can indicate the general health of the urinary tract ; protein (albumin) tests may tell something about the condition of the kidneys and prostate and, in a pregnant women, indicate toxemia ; glucose (sugar
in the urine could suggest diabetes ; the presence of ketone bodies could be a sign of metabolic disorders ; bilirubin (bile) in the urine could be a sign of liver disease, and so on.Various urine tests check for the presence of red blood cells or white
blood cells, tissue cells from the lining of organs, various hormones, traces of drugs taken. Fat bodies, parasites, indications of renal calculi (kidney stones), and a variety of bits of tissue, often microscopic, called
casts. One kind of cast might be a sign ofheart failure or shock, another might be a warning of heavy metal poisoning, a third might indicate a kidney infection.