The importance of the kidney functions has been clearly demonstrated. Urine, which is the fluid secreted by these organs, is one of the most important sources of information, not only as to the manner in which the body utilizes food in health, but as an index to certain pathological conditions, the processes of which are more or less indicated by the products excreted in the urine.

Function of the Kidneys.—The kidneys, as has already been stated, furnish a means by which the greater part of the waste products of the body are eliminated and in addition to this function they adjust the salts in the body. In an early chapter the function of the salts in food was explained. A certain amount of these substances, we know, is absolutely necessary to carry on the work in the body, but harm comes when a surplus is retained in excess of that which can be used in performing the various processes. Consequently the function of the kidneys to adjust the salts balance is by no means their least important one.

Elimination of the Toxins.—The toxic substances manufactured in the body and those resulting from bacterial action upon unabsorbed proteins are likewise eliminated in the urine. Thus it can be readily understood how necessary it is to keep these organs in good repair, that they may continue their work in an efficient manner.

It is necessary from a pathological standpoint for the nurse to understand the making of some of the simpler tests, that she may simplify her own work and that of the physician. Excretion of Carbon Dioxide and Water.—We have already spoken of the combinations of carbon and hydrogen compounds. These substances being oxidized, the carbon dioxide produced is eliminated by way of the lungs and the water is excreted partly by way of the lungs and skin, but chiefly by way of the kidneys.

Oxidation and Excretion of Nitrogenous Substances.—When the nitrogenous substances are oxidized, the used-up oxygen products are eliminated by the kidneys in the form of urea and more or less highly oxidized substances, such as ammonia and other salts, purin bases, and creatinin.

Uric Acid, the chief of the oxidation products of nucleoproteins, is produced in the body and from food, and is always in the urine, being one of its normal constituents. It is only when this substance is in excess in the urine that a pathological condition is indicated.

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.

The Amount of Urine.—The amount of urine voided in twenty-four hours varies with the individual in health as well as in disease. Many individuals void a great quantity during the twenty-four hours, chiefly because they drink a great quantity of water and other beverages. The average amount of urine passed in twenty-four hours by an adult, or a child over eight years, is from 1000 to 2000 c.c. It represents from 60% to 70% of the amount of water ingested.

Collecting the Urine for Testing.—In measuring the urine it is necessary to begin collecting it after the bladder has been emptied the first thing in the morning. The patient should void just before the end of the twenty-four-hour period to be sure that the amount formed by the kidneys during this time is accounted for.

Diseases in Which Urine Is Diminished.—In certain diseases the amount of urine passed is diminished. This is found to be true in diarrhea and dysentery, when water is lost in the feces, in hemorrhage from any part of the body and from vomiting. It is likewise at times the case after abdominal operations and in nervous conditions, such as hysteria. The urine is diminished when there is an organic obstruction in the urinary tract and certain obstructive diseases of the heart, the lungs and the liver. In these latter cases, there is seen to be a retention or suppression of urine. In both acute and chronic nephritis and in certain fevers, the bladder at times must be emptied by means of a catheter. At other times, the condition is relieved as far as possible by limiting certain articles of food in the diet. At any rate, these points must be kept in mind when examining the urine.

Effect of Food upon the Urine.—The odor of normal urine is changed after eating certain foods, such as onions and asparagus. In disease, the odor of urine has a distinct value as a means of diagnosis; cystitis gives a foul odor, certain bacteria bringing about a decomposition in the urine and giving rise to an odor of putrefaction. In cases where there is a fistula connecting the bladder and rectum, the urine has a fecal odor.

Specific Gravity of Normal Urine.—The density or specific gravity of urine means the weight of any volume of urine as compared with that of equal volume of distilled water. The specific gravity of normal urine varies from 1012 to 1024, that is, in a thousand cubic centimeters of urine there are found from 11 to 18 grams of solid material. In health it is necessary to know the amount of urine passed in twenty-four hours, to be able to judge whether the amount of solids is too high or too low.

Specific Gravity of Diabetic Urine.—In conditions like diabetes mellitus, where there is a wastage of sugar taking place in the body—that is, instead of being oxidized to carbon dioxide and water and glucose, the sugar is passing into the urine without completing its oxidation—the specific gravity rises in these cases to 1030 and over, showing distinctly that a greater amount of solid material is in the urine than is present normally. In chronic Bright’s disease and diabetes insipidus, the specific gravity is low.

Method of Determining Specific Gravity.—The specific gravity is determined by the use of an instrument known as a urinometer. The urine is poured into a tube and the urinometer is dropped into it. The different figures are marked upon the stem of the instrument and it is a simple matter to read off the figures of the level to which the stem sinks.

Reaction to Litmus.—In a former chapter it was stated that normal urine was, as a rule, acid, that is, it turns blue litmus red. Certain diseases render the urine alkaline. A like result is brought about upon the ingestion of sodium citrate or bicarbonate of soda. Urine which stands and becomes decomposed is alkaline in reaction, due to the bacterial action, with the production of ammonia.

Albumen in the Urine.—The presence of albumen in the urine is important, since normal urine does not contain this material in quantities sufficient to be recognized by ordinary tests. Hence in disease its presence is an indication of pathological processes taking place either in the kidney or the urinary passages. The chief abnormal condition indicated by the presence of albumen in the urine is nephritis. Traces of albumen may occur in patients with fever or a heart weakness. Blood and pus in the urine likewise indicate albumen. When the nephritic condition is chronic, the kidneys themselves are diseased and the presence of albumen may be in traces only, while during the acute attack large quantities may be passed, but the urine will clear up after a time.

Benedict’s Qualitative Sugar Test.—Boil 5 c.c. of Benedict’s solution; add 8 drops of urine to be examined; hold the tube over the flame and allow to boil vigorously for 3 minutes and set aside to cool of itself. In the presence of sugar the entire solution will be filled with a precipitate which may be greenish, yellow, or red, according to the amount of sugar present. When the percentage of sugar is low (under 0.3%) the precipitate will form only upon the cooling of the solution. If there is no sugar present, the solution will either remain clear or show a slight turbidity, due to the precipitation of urates. The nurse must remember that to be useful the test must be made accurately. There must never be more than 10 drops of urine and 8 drops is the usual quantity. The boiling must be vigorous and the solution allowed to cool spontaneously.

Fehling’s Test for Sugar.—Fehling’s alkaline solution and Fehling’s copper solution must be kept in separate bottles until ready for use. Then about 2 c.c. of Fehling’s alkaline solution is poured into a test tube and 2 c.c. of Fehling’s copper solution is added. This is diluted with hydrant water to 8 c.c. Half of this quantity is sufficient for the test. The upper half of the solution is boiled over flame (gently agitated while heating), and while still boiling a few drops of urine are added. If no change appears, it is boiled again and a few drops more of urine are added. If a reddish precipitate appears, sugar is present. The chemical reaction taking place is the reduction of copper sulphate to cuprous oxide. Sometimes a partial reduction occurs when urates are in excess, but once having seen the real reduction, a partial one cannot mislead the examiner.

Haines’s Test.—Pour 1 teaspoonful of Haines’s solution into a test tube and boil gently over a Bunsen burner; add 6 or 8 drops of urine and again heat to boiling. A yellow or red precipitate will indicate the presence of glucose.

QUANTITATIVE TEST FOR SUGAR

Benedict’s Test.[110]—The simple quantitative test for sugar is the one devised by Benedict. This is simpler than the polariscopic examination and better suited for ordinary use.

Place 5 c.c. of Benedict’s quantitative solution in a small dish, add a little less than one-fourth of a teaspoonful of sodium carbonate and one-eighth of a teaspoonful of talcum and add 10 c.c. of water. Dilute urine (1 part urine to 9 parts water) except where the qualitative test showed a low percentage of sugar, that is, when the precipitate turns green instead of yellow, in which case it will be unnecessary to dilute the urine. Place dish over burner and bring the contents to a boil. Pour the urine into a graduated pipette. Now add the urine drop by drop to the contents in the dish until the blue color entirely disappears. This test should be done over several times to assure an accurate calculation. The calculation is made as follows: 5 c.c. of Benedict’s quantitative copper solution are reduced by 0.01 gram of glucose, consequently the quantity of undiluted urine required to reduce 5 c.c. Benedict’s solution contains 0.01 gram of glucose.

Example; 1500 c.c. urine in 24 hours. 5 c.c. used to reduce (decolorized) Benedict’s solution.

1500 × 0.002 (0.2 per cent.) = 3 grams of sugar in 24 hours.

Example: If the urine had been diluted with 9 parts water, in other words, 10 times, the calculation would be 5 c.c. diluted urine = 0.5 c.c. actual urine.

1500 × 0.02 (2 per cent.) = 30 grams of sugar in 24 hours.

Hill and Eckman perform the Benedict’s quantitative test as follows:[111]

Measure with a pipette 25 c.c. Benedict’s solution into a porcelain dish, add 5 or 10 grams approximately of solid sodic carbonate, heat to boiling, and while boiling, run in urine until a white precipitate forms, then add urine more slowly until the last trace of blue disappears. The urine should be diluted so that not less than 10 c.c. will be required to amount of sugar which 25 c.c. of reagent is capable of oxidizing.

Calculation: 5 divided by number of cubic centimeters of urine run in equals per cent. of sugar.

Fermentation Test for Quantity of Sugar in Urine.—If the urine is 70° F. (room) temperature when the specific gravity is taken at both the beginning and end of the test, it will assure accuracy. To 100 c.c. of urine of known specific gravity, add one-fourth of fresh yeast cake thoroughly broken up. Mix thoroughly and set aside at a temperature between 85° and 95° F. for twenty-four hours, after which time test with Benedict’s or Fehling’s solutions. If reduction is obtained, it will be necessary to allow the fermentation to continue until it is complete. When no further reduction is obtained, the specific gravity is taken after the urine has reached a temperature of 76°. The difference in the specific gravity at the beginning and end of the test multiplied by 0.23 gives the percentage of sugar in the urine.

The following formulas represent the various solutions used in the above test:

Benedict’s Qualitative Solution

Fehling’s Solution

Haines’s Solution

Benedict’s (Quantitative) Solution

Dissolve the carbonate, citrate, and sulphocyanide with the aid of heat and enough water to make 800 c.c. of mixture. (Filter, if necessary.) Weigh exactly the copper sulphate crystals and dissolve in 100 c.c. of water, now add it to the first solution; stirring constantly. Add the ferrocyanide solution; cool and dilute to exactly 1 liter.

50 mg. (0.050 gm.) of sugar will reduce 25 c.c. of the above solution.

Gerhardt’s Ferric Chloride Reaction for Diacetic Acid.—To 10 c.c. of fresh urine, add carefully a few drops at a time of undiluted aqueous solution of ferric chloride U.S.P. A precipitate of ferric phosphates first forms, but upon the addition of a few more drops of the same solution it is dissolved. A Burgundy red (red wine) color is obtained in the presence of diacetic acid. The depth of this color is indicative of the quantity of acid present. Joslin[112] records the intensity of the reaction as follows, +, ++, +++, or ++++.

According to Joslin, it must be remembered that similar reaction is obtained in the urine of individuals taking salicylates, antipyrin, cyanates, or acetates, but it is a simple process to differentiate between the color produced as a result of diacetic acid and that produced by the above-mentioned drugs. If the solution is boiled for two minutes, the color from diacetic acid will disappear, owing to the unstableness of that substance, while that from the drugs will remain unchanged.

Test for Acetone.—Pour 5 c.c. of urine to be tested into a test tube, add a crystal of sodium nitroprusside, acidify with glacial acetic acid, shake well, and then make alkaline with ammonium hydrate. The presence of acetone is indicated by a purple color.

TESTS FOR ALBUMEN

The heat test[113] is the simplest. This consists of first filtering the urine through filter paper, then pouring some of the clear urine into a test tube, holding the test tube in a flame so that only the upper layer boils, then adding a few drops of 2% solution of acetic acid and boiling again. If there is albumen present, a very faint, or a heavy cloudiness (precipitate of coagulated albumen) forms on boiling and persists or becomes heavier on the addition of a few drops of dilute acetic acid (2%) and boiling again. If a precipitate occurs at the first boiling, but clears up again entirely on adding acetic acid, it is not albumen but harmless phosphates or carbonates.

HELLER’S TEST FOR ALBUMEN

Into a test tube pour a few drops of nitric acid, filter the urine and allow a small quantity of it to trickle from a pipette down the side of a test tube until it comes in contact with the acid. If albumen is present a distinctly formed white ring is seen at the zone of contact.

TEST FOR INDICAN

This material is found in cases of obstinate constipation and in other intestinal disturbances where the passage of the food mass in the small intestines is delayed and the putrefactive bacteria exert their activities upon the unabsorbed protein.

Test.—Mix equal quantities of urine and fresh hydrochloric acid and add drop by drop fresh concentrated solution of chloride of lime (5 to 1,000). Indican is indicated by the appearance of a blue color.

SUMMARY

Urinalysis represents one of the most important means for determining the health of an individual, since it is the urine that shows those substances produced in the body as a result of the breaking down of the body tissues and protein foods.

Composition of Normal Urine must be familiar to the nurse in order that she may recognize any change taking place in the urine of her patient which may indicate pathological conditions in the body.

The Specific Gravity of urine is one of the points by means of which the presence of certain substances more or less abnormal in character is determined.

Other Points, such as color, odor, quantity, reaction, and chemical composition, likewise show any deviation from the normal in the individual.

Urine Tests are necessary to determine the composition of the secretion. The character of these tests and the methods used in making them form an essential part in the training of the nurse.

Tests for the presence of albumen, sugar, and possibly indican in the urine, should be made by the nurse. The latter substance represents the extent of putrefaction taking place in the body and for this reason should be included in the urine tests.

Collecting the Urine for testing is important. The amount includes all that has been voided throughout the entire twenty-four hours beginning after the bladder has been emptied on the first morning and ending after the first specimen has been voided on the morning of the second day.

Preserving the Urine for testing is usually necessary, especially during the warm weather. The specimens should be collected in a wide-mouthed sterile glass jar. This should be kept in a cold place. Some harmless preservative such as chloroform should be added to assure its keeping.

PROBLEMS

(a) Outline tests used in urinalysis; state when they are used.

(b) List the equipment needed for making the simple tests.

(c) Make tests in laboratory and list results in note-book.