Urine Analysis

A complete urine analysis includes taking the specific gravity of the urine, testing its reaction, determining the total quantity of solids and the percentages of the various solids, such as urea, extractives, and salts. As a rule, nurses need to know only the tests for substances, such as albumin, glucose, acetone, and diacetic acid, which, in certain diseases, it is necessary to keep track of from day to day, but a few other tests are described here since it is interesting to know how the data contained in the urine-analysis reports sent from the laboratory are obtained.

The method of testing the specific gravity of liquids was described in Chapter III. and the manner of ascertaining their reaction was mentioned in Chapter XIV.

Methods of determining the total quantity of solids. Stir the specimen of urine, or else shake the flask containing it, so that if any sediment has precipitated it will become mixed with the liquid portion of the urine. Then pour 25 c.c., or other definite measure, of the urine into an evaporating dish, place this in a water bath over a flame, and let it remain until the water of the urine has evaporated and the residue is perfectly dry. Weigh the dish with the residue and deduct the weight of the former from the total. The amount remaining will be the weight of the residue and will show the quantity of solid matter in the amount of urine taken.

When only an approximate estimate of the total solids is required, it is often calculated by multiplying the two last figures of the specific gravity by 2.33. Thus, if the urine has a specific gravity of 1.025, there

will be 58.25 grains of solid matter contained in 1000 grains of the urine; since 25 X 2.33 = 58.25.

A test for acetone.-To 10 c.c. of urine, in a test tube, add about 20 drops of concentrated NaOH and 5 drops of a 5% solution of sodium nitroprussid. If acctone is present, the mixture becomes red and the red changes to purple upon the addition of an excess (i.e., a larger quantity than there is of the mixture) of glacial acetic acid.

A test for diacetic acid.-Add, drop by drop, some ferric chlorid solution to about 5 c.c. of the urine until a precipitate ceases to form; filter the mixture, to remove the precipitate, and add some more ferric chlorid to the filtrate. If diacetic acid is present a deep red color will develop. As other substances, such as those excreted after taking salicylic acid and similar drugs, give the same reaction, the solution is boiled, and if the color is due to diacetic acid, it will disappear, the acid being thereby changed to acetone, but color due to the other substances will be permanent.

Albumin tests.-The heat test for albumin was described on page 284. The Heller test, another of the tests in common use, is as follows: Pour about 3 c.c. of concentrated nitric acid into a test tube and, with a pipet, add, slowly, so as to avoid mixing the two liquids, about 3 c.c. of filtered urine. A white ring at the junction of the fluids shows the presence of albumin in the urine.

Tests for glucose.-Several of the common tests for glucose were given in Chapter XVIII.

A test for indican.-Put about 4 to 6 drops of a 1% solution of potassium permanganate into a test tube, add between 1 and 2 c.c. of chloroform, then 10 c.c.

of hydrochloric acid, and lastly 10 c.c. of the urine. Invert the test tube two or three times so as to thoroughly mix its contents and allow it to stand for about 5 minutes. If indican is present in the urine, it will be broken down by the hydrochloric acid and oxidized by the potassium permanganate to indigo, which is dissolved in the chloroform and gives a blue color, the shade of which varies with the amount of indican present, being very pale if there is only a slight trace.

A test for bile.-One of the tests for bile very commonly used is that known as Gmelin's test, which is as follows: To 5 c.c. of concentrated HNO3, in a test tube, add 2 to 3 c.c. of urine, pouring the latter down the side of the tube so that the two liquids will not become mixed. If bile is present, circles of various colors will form where the liquids come in contact.

A test for blood (Heller's test).-Add enough NaOH to 10 c.c. of urine to make the latter decidedly alkaline, boil this, and then let it stand. If blood is present the alkali converts the pigment into hematin which is precipitated as a red deposit. As there are other substances sometimes present in urine that give the same reaction, filter the liquid and pour a little acetic acid over the precipitate. If this consists of substances other than hematin, it will be entirely dissolved; hematin may be slightly, but it will not be wholly, dissolved.

A test for pus.-Before testing urine for pus, let it stand undisturbed so that any sediment present will fall to the bottom, then pour off as much of the overlying liquid as possible without disturbing the sediment, and to the latter add some concentrated

NaOH or KOH solution or some strong NH OH. If there is pus in the sediment, it will be converted into a viscid mass. If mucus is present, it will be curded, but it will not assume the tough, gelatinous appearance that the pus does.

GLOSSARY

Alloy, a mixture of two or more metals of differing nature and value.

Anhydrid, an oxid which unites with water to form an acid; a substance formed from a compound, especially an acid, by the loss of a molecule of water.

Anion, a negative ion.

Anneal, to render a substance less brittle by heating it to a high temperature and then cooling it slowly.

Anode, the positive pole of an electric cell.

Apposition, in contact with.

Arbitrarily, depending on the will of an umpire, judge, etc.

Binary, composed of two elements.

Calcareous, pertaining to or of the nature of lime.

Cathode, the negative pole of an electric cell.

Cation, an electro-positive ion.

Caustic, corrosive.

Colloid, glutinous; resembling glue; a non-crystalline substance. Commercial, as ordinarily furnished by dealers.

Conifers, trees that bear cones.

Decomposition, the separation of a substance into simpler

parts.

Deflagration, sudden, rapid burning.

Deflected, bent from a straight line; turned aside.

Degeneration, changing from a higher to a lower form.

Dehydration, removal of water from a substance.

Deliquescence, see page 222.

Detergent, cleansing.

Diaphragm, a partition, such as a membrane stretched between two cavities.

Dissociation, partial decomposition.

Ductile, pliant; easily stretched.