Examination of the Urine, then, is made for several different purposes: (1) to ascertain whether the kidneys are doing their work properly; (2) to find if the kidneys, or any part of the urinary tract, are either temporarily or permanently diseased; (3) to be able to judge from the various substances in the urine whether there is any abnormal process taking place in the body.
Tests.—In the examination of the urine for the above purposes, certain definite tests are made. These tests differentiate between the abnormal and the normal.
(1) Color.
(2) Amount in twenty-four hours.
(3) Odor.
(4) Specific gravity.
(5) Reaction, acid or alkaline.
(6) Albumen, indican, acetone bodies.
(7) Sugar.
(8) Microscopic examination for casts, cells, bacteria, etc.
The Color of normal urine varies, especially with the amount voided.
The variations in color range from the pale straw color of individuals who are voiding large quantities to the deep lemon or amber of those who void much less.
Pathological conditions are indicated to a certain extent by the color of the urine. Fevers heighten the color, small quantities of blood cause a smoky appearance, while bile changes the color of the urine to a greenish yellow.
Precipitates in the Urine.—When the urine has been allowed to stand for a time there is sometimes a brick-red deposit due to the precipitate of urates. This disappears upon heating and is not an evidence of any diseased condition.
Turbidity of Urine.—The turbidity of fresh urine then is the only kind which need be considered, since standing in the cold often brings about this condition, due to the growth of bacteria and deposits of both phosphates and urates.
Requirements in Testing Urine.—Urine to be tested should be fresh, and when it is not possible to make the examination at once it should be preserved with chloroform, or some other harmless preservative, until ready to use.
Bacteria in Urine.—The changes due to bacterial growth in the urine are manifested not only by the turbid character of the urine but also by the odor of ammonia.