THE URINE
Preliminary Considerations.--The urine is an aqueous solution of
various organic and inorganic substances. It is probably both a
secretion and an excretion. Most of the substances in solution are
either waste-products from the body metabolism or products derived
directly from the foods eaten. Normally, the total amount of solid
constituents carried off in twenty-four hours is about 60 gm., of
which the organic substances make up about 35 gm. and the inorganic
about 25 gm.
The chief organic constituents are urea and uric acid. Urea
constitutes about one-half of all the solids, or about 30 gm. in
twenty-four hours.
The chief inorganic constituents are the chlorids, phosphates, and
sulphates. The chlorids, practically all in the form of sodium
chlorid, constitute one-half, or about 13 gm., in twenty-four hours.
Certain substances appear in the urine only in pathologic conditions.
The most important of these are proteids, sugars, acetone and related
substances, bile, hemoglobin, and the diazo substances.
In addition to the substances in solution all urines contain various
microscopic structures.
While, under ordinary conditions, the composition of urine does not
vary much from day to day, it varies greatly at different hours of the
same day. It is evident, {48} therefore, that _no quantitative test
can be of value unless a sample of the mixed twenty-four-hour urine be
used_. The patient should be instructed to void all the urine during
the twenty-four hours into a clean vessel kept in a cool place, to mix
it well, to measure the whole quantity, and to bring four to eight
ounces for examination. When it is desired to make only qualitative
tests, as for albumin or sugar, a "sample" voided at random will
answer. It should be remembered, however, that urine passed about
three hours after a meal is most likely to contain pathologic
substances. That voided first in the morning is least likely to
contain them.
The urine must be examined while fresh. Decomposition sets in rapidly,
especially in warm weather, and greatly interferes with all the
examinations. Decomposition may be delayed by adding five grains of
boric acid (as much of the powder as can be heaped upon a ten-cent
piece) for each four ounces of urine. Formalin, in proportion of one
drop to four ounces, is also an efficient preservative, but if larger
amounts be used, it may give reactions for sugar and albumin, and is
likely to cause a precipitate which greatly interferes with the
microscopic examination.
Normal and abnormal pigments, which interfere with certain of the
tests, can be removed by filtering the urine through animal charcoal,
or precipitating with a solution of acetate of lead and filtering.
A suspected fluid can be identified as urine by detecting any
considerable quantity of urea in it (p. 66). Traces of urea may,
however, be met with in ovarian cyst fluid, while urine from very old
cases of hydronephrosis may contain little or none.
{49} Clinical examination of the urine may conveniently be considered
under four heads: I. Physical examination. II. Chemic examination.
III. Microscopic examination. IV. The urine in disease.
I. PHYSICAL EXAMINATION
1. Quantity.--The quantity passed in twenty-four hours varies greatly
with the amount of liquids ingested, perspiration, etc. The normal may
be taken as 1000 to 1500 c.c., or 40 to 50 ounces.
The quantity is increased (polyuria) during absorption of large serous
effusions and in many nervous conditions. It is usually much increased
in chronic interstitial nephritis, diabetes insipidus, and diabetes
mellitus. In these conditions a permanent increase in amount of urine
is characteristic--a fact of much value in diagnosis. In diabetes
mellitus the urine may, though rarely, reach the enormous amount of 50
liters.
The quantity is decreased (oliguria) in severe diarrhea; in fevers; in
all conditions which interfere with circulation in the kidney, as
poorly compensated heart disease; and in the parenchymatous forms of
nephritis. In uremia the urine is usually very greatly decreased and
may be entirely suppressed (anuria).
2. Color.--This varies considerably in health, and depends largely
upon the quantity of urine voided. The usual color is yellow or
reddish-yellow, due to the presence of several pigments, chiefly
urochrome. In recording the color Vogel's scale (see _Frontispiece_)
is very widely used, the urine being filtered and examined by
transmitted light in a glass three or four inches in diameter.
The color is sometimes greatly changed by abnormal {50} pigments.
Blood-pigment gives a red or brown, smoky color. Urine containing bile
is yellowish or brown, with a yellow foam when shaken. It may assume a
greenish hue after standing, owing to oxidation of bilirubin into
biliverdin. Ingestion of small amounts of methylene-blue gives a pale
green; large amounts give a marked blue. Santonin produces a yellow;
rhubarb, senna, cascara, and some other cathartics, a brown color;
these change to red upon addition of an alkali, and if the urine be
alkaline when voided may cause suspicion of hematuria. Thymol gives a
yellowish-green. Following poisoning from phenol and related drugs the
urine may have a normal color when voided, but becomes olive-green to
brownish-black upon standing. Urine which contains melanin, as
sometimes in melanotic sarcoma and, very rarely, in wasting diseases,
also becomes brown or black upon long standing.
3. Transparency.--Freshly passed normal urine is clear. Upon standing,
a faint cloud of mucus, leukocytes, and epithelial cells settles to
the bottom. Abnormal cloudiness is usually due to presence of
phosphates, urates, pus, blood, or bacteria.
_Amorphous phosphates_ are precipitated in neutral or alkaline urine.
They form a white cloud and sediment which disappear upon addition of
an acid.
_Amorphous urates_ are precipitated only in acid urine. They form a
white or pink cloud and sediment ("brick-dust deposit") which
disappear upon heating.
_Pus_ resembles amorphous phosphates to the naked eye. Its nature is
easily recognized with the microscope, or by adding a strong solution
of caustic soda to the sediment, which is thereby transformed into a
gelatinous mass (Donné's test).
{51} _Blood_ gives a reddish or brown, smoky color, and may be
recognized with the microscope or by tests for hemoglobin.
_Bacteria_, when present in great numbers, give a uniform cloud which
cannot be removed by ordinary filtration. They are detected with the
microscope.
The cloudiness of decomposing urine is due mainly to precipitation of
phosphates and multiplication of bacteria.
4. Reaction.--Normally, the mixed twenty-four-hour urine is slightly
acid in reaction, the acidity being due to acid salts, not to free
acids. Individual samples may be slightly alkaline, especially after a
full meal. The reaction is determined by means of litmus paper.
Acidity is increased after administration of certain drugs, and
whenever the urine is concentrated from any cause, as in fevers. A
very acid urine may cause frequent micturition because of its
irritation. This is often an important factor in the troublesome
enuresis of children.
The urine always becomes alkaline upon long standing, owing to
decomposition of urea with formation of ammonia. If markedly alkaline
when voided, it usually indicates such "ammoniacal decomposition" in
the bladder, which is the rule in chronic cystitis, especially that
due to paralysis or obstruction. Alkalinity due to ammonia (_volatile
alkalinity_) can be distinguished by the fact that litmus paper turned
blue by the urine again becomes red upon gentle heating. _Fixed
alkalinity_ is due to alkaline salts, and is often observed during
frequent vomiting, after the crisis of pneumonia, in various forms of
anemia, after full meals, and after administration of certain drugs,
especially salts of vegetable acids.
5. Specific Gravity.--The normal average is about {52} 1.017 to 1.020.
Samples of urine taken at random may go far above or below these
figures, hence a sample of the mixed twenty-four-hour urine should
always be used.
Pathologically, it may vary from 1.001 to 1.060. It is _low_ in
chronic interstitial nephritis, diabetes insipidus, and many
functional nervous disorders. It is _high_ in fevers and in
parenchymatous forms of nephritis. In any form of nephritis a sudden
fall without a corresponding increase in quantity of urine may
foretell approaching uremia. It is _highest_ in diabetes mellitus. A
high specific gravity when the urine is not highly colored should lead
one to suspect this disease. A normal specific gravity does not,
however, exclude it.
[Illustration: FIG. 14.--Squibb's urinometer with thermometer and
cylinder.]
The specific gravity is most conveniently estimated by means of the
urinometer--Squibb's is preferable (Fig. 14). It is standardized for a
temperature of 77° F., and the urine should be at or near that
temperature. Care should be taken that the urinometer does not touch
the side of the tube, and that air-bubbles are removed from the
surface {53} of the urine. With most instruments the reading is taken
from the bottom of the meniscus.
One frequently wishes to ascertain the specific gravity of quantities
of fluid too small to float an urinometer. A simple device for this
purpose, which requires only about 3 c.c. and is very satisfactory in
clinical work, has been designed by Saxe (Fig. 15). The urine is
placed in the bulb at the bottom, the instrument is floated in
distilled water, and the specific gravity is read off from the scale
upon the stem.
[Illustration: FIG. 15.--Saxe's urinopyknometer and jar for same.]
6. Total Solids.--An estimation of the total amount of solids which
pass through the kidneys in twenty-four hours is, in practice, one of
the most useful of urinary {54} examinations. The normal for a man of
150 pounds is about 60 grams, or 950 grains. The principal factors
which influence this amount are body weight (except with excessive
fat), diet, exercise, and age, and these should be considered in
making an estimation. After about the forty-fifth year it becomes
gradually less; after seventy-five years it is about one-half the
amount given.
In disease, the amount of solids depends mainly upon the activity of
metabolism and the ability of the kidneys to excrete. An estimation of
the solids, therefore, furnishes an important clue to the functional
efficiency of the kidneys. The kidneys bear much the same relation to
the organism as does the heart: they cause no direct harm so long as
they are capable of performing the work required of them. When,
however, through either organic disease or functional inactivity, they
fail to carry off their proportion of the waste-products of the body,
some of these products must either be eliminated through other organs,
where they cause irritation and disease, or be retained within the
body, where they act as poisons. The great importance of these poisons
in production of distressing symptoms and even organic disease is not
well enough recognized by most practitioners. Disappearance of
unpleasant and perplexing symptoms as the urinary solids rise to the
normal under proper treatment is often most surprising.
When, other factors remaining unchanged, the amount of solids
eliminated is considerably above the normal, increased destructive
metabolism may be inferred.
The total solids can be estimated roughly, but accurately enough for
most clinical purposes, by multiplying the last two figures of the
specific gravity of the mixed {55} twenty-four-hour urine by the
number of ounces voided and to the product adding one-tenth of itself.
This gives the amount in grains. Häser's method is more widely used
but is less convenient. The last two figures of the specific gravity
are multiplied by 2.33. The product is then multiplied by the number
of cubic centimeters voided in twenty-four hours and divided by 1000.
This gives the total solids in grams.
7. Functional Tests.--Within the past few years much thought has been
devoted to methods of more accurately ascertaining the functional
efficiency of the kidneys, especially of one kidney when removal of
the other is under consideration. The most promising of the methods
which have been devised are cryoscopy, the methylene-blue test, and
the phloridzin test. It is doubtful whether, except in experienced
hands, these yield any more information than can be had from an
intelligent consideration of the specific gravity and the
twenty-four-hour quantity, together with a microscopic examination.
They are most useful when the urines obtained from separate kidneys by
segregation or ureteral catheterization are compared. The reader is
referred to larger works upon urinalysis for details.
_Cryoscopy_, determination of the freezing-point, depends upon the
principle that the freezing-point of a fluid is depressed in
proportion to the number of molecules in solution. To have any value,
the freezing-point of the urine must be compared with that of the
blood, since it is not so much the number of molecules contained in
the urine as the number which the kidney has failed to carry off and
has left in the blood, that indicates its insufficiency.
{56} In the _methylene-blue test_ of Achard and Castaigne a solution
of methylene-blue is injected intramuscularly, and the time of its
appearance in the urine is noted. Normally, it appears in about thirty
minutes. When delayed, renal "permeability" is supposed to be
interfered with.
The _phloridzin test_ consists in the hypodermic injection of a small
quantity of phloridzin. This substance is transformed into glucose by
the kidneys of healthy persons. In disease, this change is more or
less interfered with, and the amount of glucose recoverable from the
urine is taken as an index of the secretory power of the kidneys.
In applying these tests for "permeability," "secretory ability," etc.,
one must remember that the conditions are abnormal, and that there is
no evidence that the kidneys will behave with the products of
metabolism as they do with the substances selected for the tests, and
also that the tests throw unusual work upon the kidneys, which in some
cases may be harmful.
II. CHEMIC EXAMINATION
A. NORMAL CONSTITUENTS
The most important are chlorids, phosphates, sulphates including
indican, urea, and uric acid.
1. Chlorids.--These are derived from the food, and are mainly in the
form of sodium chlorid. The amount excreted normally is 10 to 15 grams
in twenty-four hours. It is much affected by the diet.
Excretion of chlorids is diminished in nephritis and in fevers,
especially in pneumonia and inflammations leading to the formation of
large exudates. In nephritis the {57} kidneys are less permeable to
the chlorids, and it is probable that the edema is due largely to an
effort of the body to dilute the chlorids which have been retained. In
fevers the diminution is due largely to decrease of food. In pneumonia
chlorids are constantly very low, and in some cases are absent
entirely. Following the crisis they are increased. In inflammations
leading to formation of large exudates--_e.g._, pleurisy with
effusion--chlorids are diminished, because a considerable amount
becomes "locked up" in the exudate. During absorption chlorids are
liberated and appear in the urine in excessive amounts.
[Illustration: FIG. 16.--The Purdy electric centrifuge.]
_Quantitative Estimation_.--The best method for clinical purposes is
the centrifugal method.
{58} _Purdy's Centrifugal Methods_.--As shown by the late Dr. Purdy,
the centrifuge offers an important means of making quantitative
estimations of a number of substances in the urine. Results are easily
and quickly obtained, and are probably accurate enough for all
clinical purposes.
[Illustration: FIG. 17.--Water-motor centrifuge.]
In general, the methods consist in precipitating the substance to be
estimated in a graduated centrifuge tube, and applying a definite
amount of centrifugal force for a definite length of time, after which
the percentage of precipitate is read off upon the side of the tube.
Albumin, if present, must be previously removed by boiling and
filtering. Results are in terms of _bulk of precipitate_, which must
not be confused with _percentage by weight_. The weight percentage can
be found by referring to Purdy's tables, given later. In this, as in
all quantitative urine work, percentages mean little in themselves;
the actual {59} amount eliminated in twenty-four hours should always
be calculated.
The centrifuge should have an arm with radius of 6¾ inches when in
motion, and should be capable of maintaining a speed of 1500
revolutions a minute. The electric centrifuge is to be recommended,
although good work can be done with a water-power centrifuge, or,
after a little practice, with the hand centrifuge. A speed indicator
is desirable with electric and water-motor machines, although one can
learn to estimate the speed by the musical note.
[Illustration: FIG. 18.--Purdy's tubes for the centrifuge: _a_,
Percentage tube; _b_, sediment tube.]
* * * * *
Estimation of Chlorids.--Fill the graduated tube to the 10 c.c. mark
with urine; add 15 drops strong nitric acid and then silver nitrate
solution (dram to the ounce) to the 15 c.c. mark. Mix by inverting
several times. Let stand a few minutes for a precipitate to form, and
then revolve in the centrifuge for three minutes at 1200 revolutions a
minute. Each one-tenth cubic centimeter of precipitate equals 1 per
cent. by bulk. The normal is about 10 per cent. This may be converted
into terms of chlorin or sodium chlorid by means of the table upon
page 60. Roughly speaking, the percentage of chlorin by weight is
about one-twelfth the bulk-percentage.
{60} TABLE FOR THE ESTIMATION OF CHLORIDS AFTER CENTRIFUGATION
_Showing the bulk-percentage of silver chlorid (AgCl) and the
corresponding gravimetric percentages and grains per fluidounce of
sodium chlorid (NaCl) and chlorin (Cl).--(Purdy.)_
Bulk-percentage | Percentage | Gr. Per | Percentage | Gr. Per
of AgCl. | NaCl. | Oz. NaCl. | Cl. | Oz. Cl.
----------------+------------+-----------+------------+--------
¼ | 0.03 | 0.15 | 0.02 | 0.1
½ | 0.07 | 0.31 | 0.04 | 0.19
¾ | 0.1 | 0.47 | 0.06 | 0.28
1 | 0.13 | 0.62 | 0.08 | 0.38
1¼ | 0.16 | 0.78 | 0.1 | 0.48
1½ | 0.19 | 0.93 | 0.12 | 0.57
1¾ | 0.23 | 1.09 | 0.14 | 0.67
2 | 0.26 | 1.24 | 0.16 | 0.76
2¼ | 0.29 | 1.41 | 0.18 | 0.85
2½ | 0.32 | 1.56 | 0.2 | 0.96
2¾ | 0.36 | 1.71 | 0.22 | 1.04
3 | 0.39 | 1.87 | 0.24 | 1.13
3¼ | 0.42 | 2.02 | 0.26 | 1.23
3½ | 0.45 | 2.18 | 0.28 | 1.32
3¾ | 0.49 | 2.35 | 0.3 | 1.42
4 | 0.52 | 2.49 | 0.32 | 1.51
4¼ | 0.55 | 2.64 | 0.34 | 1.61
4½ | 0.58 | 2.8 | 0.35 | 1.7
4¾ | 0.62 | 2.96 | 0.37 | 1.8
5 | 0.65 | 3.11 | 0.39 | 1.89
5½ | 0.71 | 3.42 | 0.43 | 2.09
6 | 0.78 | 3.73 | 0.47 | 2.27
6½ | 0.84 | 4.05 | 0.51 | 2.46
7 | 0.91 | 4.35 | 0.55 | 2.62
7½ | 0.97 | 4.67 | 0.59 | 2.84
8 | 1.04 | 4.98 | 0.63 | 3.02
8½ | 1.1 | 5.29 | 0.67 | 3.22
9 | 1.17 | 5.6 | 0.71 | 3.4
9½ | 1.23 | 5.91 | 0.75 | 3.6
10 | 1.3 | 6.22 | 0.79 | 3.79
10½ | 1.36 | 6.53 | 0.83 | 3.97
11 | 1.43 | 6.84 | 0.87 | 4.16
11½ | 1.49 | 7.2 | 0.91 | 4.35
12 | 1.56 | 7.46 | 0.95 | 4.54
12½ | 1.62 | 7.78 | 0.99 | 4.73
13 | 1.69 | 8.09 | 1.02 | 4.92
13½ | 1.75 | 8.4 | 1.06 | 5.11
14 | 1.82 | 8.71 | 1.1 | 5.29
14½ | 1.88 | 9.02 | 1.14 | 5.49
15 | 1.94 | 9.33 | 1.18 | 5.67
15½ | 2.01 | 9.65 | 1.22 | 5.86
16 | 2.07 | 9.94 | 1.26 | 6.06
16½ | 2.14 | 10.27 | 1.3 | 6.24
17 | 2.2 | 10.51 | 1.34 | 6.43
17½ | 2.27 | 10.87 | 1.38 | 6.62
18 | 2.33 | 11.2 | 1.42 | 6.81
18½ | 2.4 | 11.51 | 1.46 | 7.0
19 | 2.46 | 11.82 | 1.5 | 7.19
19½ | 2.53 | 12.13 | 1.54 | 7.38
20 | 2.59 | 12.44 | 1.58 | 7.56
----------------+------------+-----------+------------+--------
Bulk-percentage to be read on the side of the tube.
* * * * *
2. Phosphates.--Phosphates are derived largely from the food, only a
small proportion resulting from metabolism. The normal daily output of
phosphoric acid is about 2.5 to 3.5 gm.
The urinary phosphates are of two kinds: _alkaline_, which make up
two-thirds of the whole, and include the {61} phosphates of sodium and
potassium; and _earthy_, which constitute one-third, and include the
phosphates of calcium and magnesium. Earthy phosphates are frequently
thrown out of solution in neutral and alkaline urines, and as
"amorphous phosphates" form a very common sediment. This sediment
seldom indicates an excessive excretion of phosphates.
_Quantitative estimation_ does not furnish much of definite clinical
value. The centrifugal method is the most convenient.
* * * * *
TABLE FOR THE ESTIMATION OF PHOSPHATES AFTER CENTRIFUGATION
_Showing bulk-percentages of uranyl phosphate (H[UO_{2}]PO_{4}) and
the corresponding gravimetric percentages and grains per ounce of
phosphoric acid (P_{2}O_{5}).--(Purdy.)_
Bulk-percentage | Percentage | Gr. Per Oz.
of H(UO_{2})PO_{4}. | P_{2}O_{5}. | P_{2}O_{5}.
--------------------+-------------+------------
½ | 0.02 | 0.1
1 | 0.04 | 0.19
1½ | 0.045 | 0.22
2 | 0.05 | 0.24
2½ | 0.055 | 0.26
3 | 0.06 | 0.29
3½ | 0.065 | 0.31
4 | 0.07 | 0.34
4½ | 0.075 | 0.36
5 | 0.08 | 0.38
6 | 0.09 | 0.43
7 | 0.1 | 0.48
8 | 0.11 | 0.53
9 | 0.12 | 0.58
10 | 0.13 | 0.62
11 | 0.14 | 0.67
12 | 0.15 | 0.72
13 | 0.16 | 0.77
14 | 0.17 | 0.82
15 | 0.18 | 0.86
16 | 0.19 | 0.91
17 | 0.2 | 0.96
18 | 0.21 | 1.0
19 | 0.22 | 1.06
20 | 0.23 | 1.1
21 | 0.24 | 1.15
22 | 0.25 | 1.2
23 | 0.26 | 1.25
24 | 0.27 | 1.3
25 | 0.28 | 1.35
--------------------+-------------+------------
Bulk-percentage to be read from graduation on the side of the tube.
Purdy's Centrifugal Method.--Take 10 c.c. urine in the graduated tube,
add 2 c.c. of 50 per cent. acetic acid, and 3 c.c. of 5 per cent.
uranium nitrate solution. Mix; let stand a few minutes, and revolve
for three minutes at 1200 revolutions. {62} The bulk of precipitate is
normally about 8 per cent. The percentage of phosphoric acid by weight
is, roughly, one-eighty-fifth of the bulk-percentage.
* * * * *
3. Sulphates.--The urinary sulphates are derived partly from the food,
especially meats, and partly from body metabolism. The normal output
of sulphuric acid is about 1.5 to 3 gm. daily.
Quantitative estimation of the total sulphates yields little of
clinical value.
* * * * *
Purdy's Centrifugal Method.--Take 10 c.c. urine in the graduated tube
and add barium chlorid solution to the 15 c.c. mark. This consists of
barium chlorid, 4 parts; strong hydrochloric acid, 1 part; and
distilled water, 16 parts. Mix; let stand a few minutes, and revolve
for three minutes at 1200 revolutions a minute. The normal bulk of
precipitate is about 0.8 per cent. The percentage by weight of
sulphuric acid is about one-fourth of the bulk-percentage.
TABLE FOR THE ESTIMATION OF SULPHATES AFTER CENTRIFUGATION
_Showing the bulk-percentages of barium sulphate (BaSO_{4}) and the
corresponding gravimetric percentages and grains per fluidounce of
sulphuric acid (SO_{3}).--(Purdy.)_
Bulk-percentage | Percentage | Gr. Per Oz.
of BaSO_{4}. | SO_{3}. | SO_{3}.
----------------+------------+------------
1/8 | 0.04 | 0.19
1/4 | 0.07 | 0.34
3/8 | 0.1 | 0.48
1/2 | 0.13 | 0.62
5/8 | 0.16 | 0.77
3/4 | 0.19 | 0.91
7/8 | 0.22 | 1.06
1 | 0.25 | 1.1
1¼ | 0.31 | 1.49
1½ | 0.37 | 1.78
1¾ | 0.43 | 2.06
2 | 0.49 | 2.35
2¼ | 0.55 | 2.64
2½ | 0.61 | 2.93
2¾ | 0.67 | 3.22
3 | 0.73 | 3.5
3¼ | 0.79 | 3.79
3½ | 0.85 | 4.08
3¾ | 0.91 | 4.37
4 | 0.97 | 4.66
4¼ | 1.03 | 4.94
4½ | 1.09 | 5.23
4¾ | 1.15 | 5.52
5 | 1.21 | 5.81
----------------+------------+------------
Bulk-percentage to be read from graduation on the side of the tube.
* * * * *
{63} Nine-tenths of the sulphuric acid is in combination with various
mineral substances (mineral or preformed sulphates). One-tenth is in
combination with certain aromatic substances, mostly products of
albuminous putrefaction in the intestine (conjugate sulphates). Among
these aromatic substances are indol, phenol, and skatol. By far the
most important of the conjugate sulphates and representative of the
group is potassium indoxyl sulphate.
Potassium indoxyl sulphate, or indican, is derived from indol. Indol
is absorbed and oxidized into indoxyl, which combines with potassium
and sulphuric acid and is thus excreted. Under normal conditions the
amount in the urine is small. It is increased by a meat diet.
Pathologically, an increase of indican always indicates abnormal
albuminous putrefaction somewhere in the body. It is noted in:
(_a_) _Diseases of the Small Intestine_.--This is by far the most
common source. Intestinal obstruction gives the largest amounts of
indican. It is also much increased in intestinal
indigestion--so-called "biliousness"; in inflammations, especially in
cholera and typhoid fever; and in paralysis of peristalsis such as
occurs in peritonitis. Simple constipation and diseases of the _large_
intestine alone do not increase the amount of indican.
(_b_) _Diseases of the stomach_ associated with deficient hydrochloric
acid, as chronic gastritis and gastric cancer. Diminished hydrochloric
acid favors intestinal putrefaction.
(_c_) _Decomposition of exudates_ anywhere in the body, as in empyema,
bronchiectasis, and large tuberculous cavities.
{64} _Detection of indican_ depends upon its decomposition and
oxidation of the indoxyl set free into indigo-blue.
* * * * *
Obermayer's Method.--In a test-tube take equal parts of the urine and
Obermayer's reagent and add a small quantity of chloroform. Mix by
inverting a few times; avoid shaking violently. If indican be present
in excess, the chloroform, which sinks to the bottom, will assume an
indigo-blue color. The depth of color indicates the comparative amount
of indican if the same proportions of urine and reagents are always
used. The indican in normal urine may give a faint blue by this
method. Urine of patients taking iodids gives a reddish-violet color,
which disappears upon addition of a few drops of strong sodium
hyposulphite solution. Bile-pigments, which interfere with the test,
must be removed (p. 48).
_Obermayer's reagent_ consists of strong hydrochloric acid (sp. gr.,
1.19), 1000 parts, and ferric chlorid, 2 parts. This makes a yellow,
fuming liquid which keeps well.
* * * * *
4. Urea.--From the standpoint of physiology urea is the most important
constituent of the urine. It is the principal waste-product of
metabolism, and constitutes about one-half of all the solids
excreted--about 30 gm. in twenty-four hours. It represents 85 to 90
per cent. of the total nitrogen of the urine, and its quantitative
estimation is a simple, though not very accurate, method of
ascertaining the state of nitrogenous excretion. Normally, the amount
is greatly influenced by exercise and diet.
Pathologically, urea is increased in fevers, in diabetes, and
especially during resolution of pneumonia and absorption of large
exudates. Other factors being equal, the amount of urea indicates the
activity of metabolism. In {65} this connection the relation between
the amounts of urea and the chlorids is important. The amount of urea
is normally about twice that of the chlorids. If the proportion is
much increased above this, increased tissue destruction may be
inferred, since other conditions which increase urea also increase
chlorids.
[Illustration: FIG. 19.--Crystals of nitrate of urea (upper half) and
oxalate of urea (lower half) (after Funke).]
Urea is decreased in diseases of the liver with destruction of liver
substance. It may or may not be decreased in nephritis. In the early
stages of chronic nephritis, when diagnosis is difficult, it is
usually normal. In the late stages, when diagnosis is comparatively
easy, it is decreased. Hence estimation of urea is of little help in
the diagnosis of this disease, especially when, as is so frequently
the case, a small quantity of urine taken at random is used. When,
however, the diagnosis is established, estimations made at frequent
intervals under the same conditions of diet and exercise are of much
value, _provided a sample of the mixed twenty-four-hour urine be
used_. A steady decline {66} is a very bad prognostic sign, and a
sudden marked diminution is usually a forerunner of uremia.
The presence of urea can be shown by allowing a few drops of the fluid
to partially evaporate upon a slide, and adding a small drop of pure
colorless nitric acid or saturated solution of oxalic acid. Crystals
of urea nitrate or oxalate (Fig. 19) will soon appear and can be
recognized with the microscope.
_Quantitative Estimation_.--The hypobromite method, which is generally
used, depends upon the fact that urea is decomposed by sodium
hypobromite with liberation of nitrogen. The amount of urea is
calculated from the volume of nitrogen set free. The improved Doremus
apparatus (Fig. 20) is the most convenient.
[Illustration: FIG. 20.--Doremus Hinds' ureometer.]
* * * * *
Pour some of the urine into the smaller tube of the apparatus, then
open the stopcock and quickly close it so as to fill its lumen with
urine. Rinse out the larger tube with water and fill it and the bulb
with 25 per cent. caustic soda solution. Add to this 1 c.c. of bromin
by means of a medicine-dropper and mix well. This prepares a fresh
solution of sodium hypobromite with excess of caustic soda, which
serves to absorb the carbon dioxid set free in the decomposition of
urea. When handling bromin, keep an open vessel of ammonia near to
neutralize the irritant fumes.
Pour the urine into the smaller tube, and then turn the stopcock so as
to let as much urine as desired (usually 1 c.c.) run slowly into the
hypobromite solution. When bubbles have ceased to rise, read off the
height of the fluid in the large {67} tube by the graduations upon its
side. This gives the amount by weight of urea in the urine added, from
which the amount excreted in twenty-four hours can easily be
calculated. If the urine contains much more than the normal amount, it
should be diluted.
To avoid handling pure bromin, which is disagreeable, Rice's solutions
may be employed:
(_a_) Bromin, 31
Potassium bromid, 31
Distilled water, 250.
(_b_) Caustic soda, 100
Distilled water, 250.
One part of each of these solutions and two parts of water are mixed
and used for the test. The bromin solution must be kept in a tightly
stoppered bottle or it will rapidly lose strength.
* * * * *
5. Uric Acid.--Uric acid is the most important of a group of
substances, called _purin bodies_, which are derived chiefly from the
nucleins of the food and from metabolic destruction of the nuclei of
the body. The daily output of uric acid is about 0.4 to 1 gm. The
amount of the other purin bodies together is about one-tenth that of
uric acid. Excretion of these substances is greatly increased by a
diet rich in nuclei, as sweetbreads and liver.
Uric acid exists in the urine in the form of urates, which in
concentrated urines are readily thrown out of solution and constitute
the familiar sediment of "amorphous urates." This, together with the
fact that uric acid is frequently deposited as crystals, constitutes
its chief interest to the practitioner. It is a very common error to
consider these deposits as evidence of excessive excretion.
Pathologically, the greatest increase of uric acid occurs {68} in
leukemia, where there is extensive destruction of leukocytes, and in
diseases with active destruction of the liver and other organs rich in
nuclei. Uric acid is decreased before an attack of gout and increased
afterward, but its etiologic relation is still uncertain. An increase
is also noted in the uric-acid diathesis and in diseases accompanied
by respiratory insufficiency.
_Quantitative Estimation_.--The following are the best methods for
ordinary clinical purposes, although no great accuracy can be claimed
for them.
[Illustration: FIG. 21.--Ruhemann's uricometer.]
* * * * *
Cook's Method for Purin Bodies.--In a centrifuge tube take 10 c.c.
urine and add about 1 gm. (about 1 c.c.) sodium carbonate and 1 or 2
c.c. strong ammonia. Shake until the soda is dissolved. The earthy
phosphates will be precipitated. Centrifugalize thoroughly and pour
off all the clear fluid into a graduated centrifuge tube. Add 2 c.c.
ammonia and 2 c.c. ammoniated silver nitrate solution. Let stand a few
minutes, and revolve in the centrifuge until the bulk of precipitate
_remains constant_. Each one-tenth cubic centimeter of sediment
represents 0.001176 gm. purin bodies. This amount may be regarded as
uric acid, since this substance usually constitutes nine-tenths of the
purin bodies and the clinical significance is the same.
_Ammoniated silver nitrate solution_ is prepared by dissolving 5 gm.
of silver nitrate {69} in 100 c.c. distilled water, and adding ammonia
until the solution clouds and again becomes clear.
Ruhemann's Method for Uric Acid.--The urine must be slightly acid.
Fill Ruhemann's tube (Fig. 21) to the mark _S_ with the indicator,
carbon disulphid, and to the mark _J_ with the reagent. The carbon
disulphid will assume a violet color. Add the urine, a small quantity
at a time, closing the tube with the glass stopper and shaking
vigorously after each addition, until the disulphid loses every trace
of its violet color and becomes pure white. This completes the test.
The figure in the right-hand column of figures corresponding to the
top of the fluid gives the amount of uric acid in parts per thousand.
The presence of diacetic acid interferes with the test.
_Ruhemann's reagent_ consists of iodin and potassium iodid, each 1.5
parts; absolute alcohol, 15 parts; and distilled water, 185 parts.
* * * * *
B. ABNORMAL CONSTITUENTS
Those substances which appear in the urine only in pathologic
conditions are of much more interest to the clinician than are those
which have just been discussed. Among them are: proteids, sugars, the
acetone bodies, bile, hemoglobin, and the diazo substances. The
"pancreatic reaction" and detection of drugs in the urine will also be
discussed under this head.
1. Proteids.--Of the proteids which may appear in the urine,
serum-albumin and serum-globulin are the most important. Mucin,
albumose, and a few others are found occasionally, but are of less
interest.
(1) Serum-albumin and Serum-globulin.--These two proteids constitute
the so-called "urinary albumin." They usually occur together, have
practically the same {70} significance, and both respond to all the
ordinary tests for "albumin."
Their presence, or _albuminuria_, is probably the most important
pathologic condition of the urine. It is either _accidental_ or
_renal_. The physician can make no greater mistake than to regard all
cases of albuminuria as indicating kidney disease.
_Accidental_ or _false albuminuria_ is due to admixture with the urine
of albuminous fluids, such as pus, blood, and vaginal discharge. The
microscope will usually reveal its nature.
_Renal albuminuria_ refers to albumin which has passed from the blood
into the urine through the walls of the kidney tubules or the
glomeruli. It probably never occurs as a physiologic condition, the
so-called "functional albuminuria" being due to obscure or slight
pathologic changes.
Renal albuminuria may be referred to one or more of the following
causes. In practically all cases it is accompanied by tube-casts.
(_a_) _Changes in the blood_ which render its albumin more diffusible,
as in severe anemias, purpura, and scurvy. Here the albumin is small
in amount.
(_b_) _Changes in circulation in the kidney_, either anemia or
congestion, as in excessive exercise, chronic heart disease, and
pressure upon the renal veins. The quantity of albumin is usually, but
not always, small. Its presence is constant or temporary, according to
the cause. Most of the causes, if continued, will produce organic
changes in the kidney.
(_c_) _Organic Changes in the Kidney_.--These include the inflammatory
and degenerative changes commonly grouped {71} together under the name
of nephritis, and also renal tuberculosis, neoplasms, and cloudy
swelling due to irritation of toxins and drugs. The amount of albumin
eliminated in these conditions varies from minute traces to 20 gm., or
even more, in the twenty-four hours, and, except in acute processes,
bears little relation to the severity of the disease. In acute and
chronic parenchymatous nephritis the quantity is usually very large.
In chronic interstitial nephritis it is small--frequently no more than
a trace. It is small in cloudy swelling from toxins and drugs, and
variable in renal tuberculosis and neoplasms. In amyloid disease of
the kidney the quantity is usually small, and serum-globulin may be
present in especially large proportion, or even alone. Roughly
distinctive of serum-globulin is the appearance of an opalescent cloud
when a few drops of the urine are dropped into a glass of distilled
water.
_Detection of albumin_ depends upon its coagulation by chemicals or
heat. There are many tests, but none is entirely satisfactory, because
other substances as well as albumin are precipitated. The most common
source of error is mucin. The tests given here are widely used and can
be recommended. They make no distinction between serum-albumin and
serum-globulin. They are given as nearly as possible in order of their
delicacy.
It is very important that urine to be tested for albumin be rendered
clear by filtration or centrifugation. This is too often neglected in
routine work. When ordinary methods do not suffice, it can usually be
cleared by shaking up with a little magnesium carbonate and filtering.
* * * * *
(1) Trichloracetic Acid Test.--The reagent consists of a saturated
aqueous solution of trichloracetic acid to which {72} magnesium
sulphate is added to saturation. A simple saturated solution of the
acid may be used, but addition of magnesium sulphate favors
precipitation of globulin, and by raising the specific gravity, makes
the test easier to apply.
Take a few c.c. of the reagent in a test-tube or conical test glass,
hold the tube or glass in an inclined position, and run the urine
gently in by means of a pipet, so that it will form a layer on top of
the reagent without mixing with it. If albumin be present, a white,
cloudy ring will appear where the two fluids come in contact. The ring
can be seen most clearly if viewed against a black background, and one
side of the tube or conical glass may be painted black for this
purpose.
[Illustration: FIG. 22.--Horismascope: adding the reagent.]
This is an extremely sensitive test, but, unfortunately, both mucin
and albumose respond to it; urates when abundant may give a confusing
white ring, and the reagent is {73} comparatively expensive. It is not
much used in routine work except as a control to the less sensitive
tests.
A most convenient instrument for applying this or any of the contact
tests is sold under the name of "horismascope" (Fig. 22).
(2) Robert's Test.--The reagent consists of pure nitric acid, 1 part,
and saturated aqueous solution of magnesium sulphate, 5 parts. It is
applied in the same way as the preceding test.
Albumin gives a white ring, which varies in density with the amount
present. A similar white ring may be produced by albumose and resinous
drugs. White rings or cloudiness in the urine above the zone of
contact may result from excess of urates or mucus. Colored rings near
the junction of the fluids may be produced by urinary pigments, bile,
or indican.
Robert's test is one of the best for routine work, although the
various rings are apt to be confusing to the inexperienced. It is more
sensitive than Heller's test, of which it is a modification, and has
the additional advantage that the reagent is not so corrosive.
(3) Purdy's Heat Test.--Take a test-tube two-thirds full of urine, add
about one-sixth its volume of saturated solution of sodium chlorid and
5 to 10 drops of 50 per cent. acetic acid. Mix, and boil the upper
inch. A white cloud in the heated portion shows the presence of
albumin.
This is a valuable test for routine work. It is simple, sufficiently
accurate for clinical purposes, and has practically no fallacies.
Addition of the salt solution, by raising the specific gravity,
prevents precipitation of mucin. Albumose may produce a white cloud
which disappears upon boiling and reappears upon cooling.
(4) Heat and Nitric Acid Test.--This is one of the oldest of the
albumin tests, and, if properly carried out, one of the best. Boil a
small quantity of filtered urine in a test-tube and add about
one-twentieth its volume of concentrated nitric {74} acid. A white
cloud or flocculent precipitate (which usually appears during the
boiling, but if the quantity be very small only after addition of the
acid) denotes the presence of albumin. A similar white precipitate,
which disappears upon addition of the acid, is due to earthy
phosphates. The acid should not be added before boiling, and the
proper amount should always be used; otherwise, part of the albumin
may fail to be precipitated or may be redissolved.
* * * * *
_Quantitative Estimation_.--The gravimetric, which is the most
reliable method, is too elaborate for clinical work. Both Esbach's,
which is very widely used, and the centrifugal method give fair
results.
* * * * *
(1) Esbach's Method.--The urine must be clear, of acid reaction, and
not concentrated. Always filter before testing, and, if necessary, add
acetic acid and dilute with water. Esbach's tube (Fig. 23) is
essentially a test-tube with a mark _U_ near the middle, a mark _R_
near the top, and graduations ½, 1, 2, 3, etc., near the bottom. Fill
the tube to the mark _U_ with urine and to the mark _R_ with the
reagent. Close with a rubber stopper, invert slowly several times, and
set aside in a cool place. At the end of twenty-four hours read off
the height of the precipitate. This gives the amount of albumin in
_grams per liter, and must be divided by 10 to obtain the percentage_.
[Illustration: FIG. 23.--Esbach's albuminometer, improved form.]
_Esbach's reagent_ consists of picric acid, 1 gm., citric acid, 2 gm.,
and distilled water, to make 100 c.c.
(2) Purdy's Centrifugal Method.--This is detailed in the accompanying
table. The percentage by weight is approximately one-fiftieth of the
bulk percentage.
{75} PURDY'S QUANTITATIVE METHOD FOR ALBUMIN IN URINE (CENTRIFUGAL)
_Table showing the relation between the volumetric and gravimetric
percentage of albumin obtained by means of the centrifuge with radius
of six and three-quarter inches; rate of speed, 1500 revolutions per
minute; time, three minutes._
VOLUMETRIC | PERCENTAGE BY | GRAINS PER
PERCENTAGE BY | WEIGHT OF | FLUIDOUNCE
CENTRIFUGE. | DRY ALBUMIN. | DRY ALBUMIN.
--------------+---------------+-------------
¼ | 0.005 | 0.025
½ | 0.01 | 0.05
¾ | 0.016 | 0.075
1 | 0.021 | 0.1
1¼ | 0.026 | 0.125
1½ | 0.031 | 0.15
1¾ | 0.036 | 0.175
2 | 0.042 | 0.2
2¼ | 0.047 | 0.225
2½ | 0.052 | 0.25
2¾ | 0.057 | 0.275
3 | 0.063 | 0.3
3¼ | 0.068 | 0.325
3½ | 0.073 | 0.35
3¾ | 0.078 | 0.375
4 | 0.083 | 0.4
4¼ | 0.089 | 0.425
4½ | 0.094 | 0.45
4¾ | 0.099 | 0.475
5 | 0.104 | 0.5
5½ | 0.111 | 0.55
6 | 0.125 | 0.6
6½ | 0.135 | 0.65
7 | 0.146 | 0.7
7½ | 0.156 | 0.75
8 | 0.167 | 0.8
8½ | 0.177 | 0.85
9 | 0.187 | 0.9
9½ | 0.198 | 0.95
10 | 0.208 | 1.0
10½ | 0.219 | 1.05
11 | 0.229 | 1.1
11½ | 0.24 | 1.15
12 | 0.25 | 1.2
12½ | 0.26 | 1.25
13 | 0.271 | 1.3
13½ | 0.281 | 1.35
14 | 0.292 | 1.4
14½ | 0.302 | 1.45
15 | 0.313 | 1.5
15½ | 0.323 | 1.55
16 | 0.333 | 1.6
16½ | 0.344 | 1.65
17 | 0.354 | 1.7
17½ | 0.365 | 1.75
18 | 0.375 | 1.8
18½ | 0.385 | 1.85
19 | 0.396 | 1.9
19½ | 0.406 | 1.95
20 | 0.417 | 2.0
20½ | 0.427 | 2.05
21 | 0.438 | 2.1
21½ | 0.448 | 2.15
22 | 0.458 | 2.2
22½ | 0.469 | 2.25
23 | 0.479 | 2.3
23½ | 0.49 | 2.35
24 | 0.5 | 2.4
24½ | 0.51 | 2.45
25 | 0.521 | 2.5
25½ | 0.531 | 2.55
26 | 0.542 | 2.6
26½ | 0.552 | 2.65
27 | 0.563 | 2.7
27½ | 0.573 | 2.75
28 | 0.583 | 2.8
28½ | 0.594 | 2.85
29 | 0.604 | 2.9
29½ | 0.615 | 2.95
30 | 0.625 | 3.0
30½ | 0.635 | 3.05
31 | 0.646 | 3.1
31½ | 0.656 | 3.15
32 | 0.667 | 3.2
32½ | 0.677 | 3.25
33 | 0.687 | 3.3
33½ | 0.698 | 3.35
34 | 0.708 | 3.4
34½ | 0.719 | 3.45
35 | 0.729 | 3.5
35½ | 0.74 | 3.55
36 | 0.75 | 3.6
36½ | 0.76 | 3.65
37 | 0.771 | 3.7
37½ | 0.781 | 3.75
38 | 0.792 | 3.8
38½ | 0.801 | 3.85
39 | 0.813 | 3.9
39½ | 0.823 | 3.95
40 | 0.833 | 4.0
40½ | 0.844 | 4.05
41 | 0.854 | 4.1
41½ | 0.865 | 4.15
42 | 0.875 | 4.2
42½ | 0.885 | 4.25
43 | 0.896 | 4.3
43½ | 0.906 | 4.35
44 | 0.917 | 4.4
44½ | 0.927 | 4.45
45 | 0.938 | 4.5
45½ | 0.948 | 4.55
46 | 0.958 | 4.6
46½ | 0.969 | 4.65
47 | 0.979 | 4.7
47½ | 0.99 | 4.75
48 | 1.0 | 4.8
_Test_.--Three cubic centimeters of 10 per cent. solution of
ferrocyanid of potassium and 2 cubic centimeters of 50 per cent.
acetic acid are added to 10 cubic centimeters of the urine in the
percentage tube and _stood aside for ten minutes_, then placed in the
centrifuge and revolved at rate of speed and time as stated at head of
the table. If albumin is excessive, dilute the urine with water until
volume of albumin falls below 10 per cent. Multiply result by the
number of dilutions employed before using the table.
* * * * *
{76} (2) Mucin (Nucleo-albumin).--Traces of the substances which are
loosely classed under this name are present in normal urine; increased
amounts are observed in irritations and inflammations of the mucous
membrane of the urinary tract. They are of interest chiefly because
they may be mistaken for albumin in most of the tests. If the urine be
diluted with water and acidified with acetic acid, the appearance of a
white cloud indicates the presence of mucin.
(3) Albumoses.--These are intermediate products in the digestion of
proteids. They have been observed in the urine in febrile and
malignant diseases and chronic suppurations, but their clinical
significance is indefinite. The following is a simple test: Mix equal
parts of the urine, which has been strongly acidified with acetic
acid, and a saturated solution of sodium chlorid. A white cloud, which
appears upon moderate heating and disappears upon boiling, shows the
presence of albumose. If the cloud increases upon boiling, albumin is
present and should be removed by filtering while hot. The cloud due to
albumose will reappear as the filtrate cools.
2. Sugars.--Various sugars may at times be found in the urine. Glucose
is by far the most common, and is the only one of clinical importance.
Levulose, lactose, and some others are occasionally met with.
(1) Glucose (Dextrose).--It is probable that traces of glucose, too
small to respond to the ordinary tests, are present in the urine in
health. Its presence in appreciable amount constitutes "glycosuria."
_Transitory_ glycosuria is unimportant, and may occur in many
conditions, as after general anesthesia and {77} administration of
certain drugs, in pregnancy, and following shock and head injuries.
_Persistent_ glycosuria has been noted in brain injuries involving the
floor of the fourth ventricle. As a rule, however, persistent
glycosuria is diagnostic of diabetes mellitus, of which disease it is
the essential symptom. The amount of glucose eliminated in diabetes is
usually considerable, and is sometimes very large, reaching 500 gm.,
or even more in twenty-four hours, but it does not bear any uniform
relation to the severity of the disease. Glucose may, on the other
hand, be almost or entirely absent temporarily.
_Detection of Glucose_.--If albumin be present in more than traces, it
must be removed by boiling and filtering.
* * * * *
(1) Haines' Test.--Take about 1 dram of Haines' solution in a
test-tube, boil, and add 6 or 8 drops of urine. A heavy yellow or red
precipitate, which settles readily to the bottom, shows the presence
of sugar. Neither precipitation of phosphates as a light flocculent
sediment nor simple decolorization of the reagent should be mistaken
for a positive reaction.
This is probably the best of the copper tests, all of which depend
upon the fact that in strongly alkaline solutions glucose reduces
copper oxid to lower grades of oxidation. They are somewhat
inaccurate, because they make no distinction between glucose and less
common forms of sugar; because certain normal substances when present
in excess, especially uric acid and creatinin, may reduce copper, and
because many drugs--_e.g._, chloral, chloroform, copaiba, acetanilid,
benzoic acid, morphin, sulphonal, salicylates--are eliminated as
copper-reducing substances. To minimize these fallacies dilute the
urine if it be concentrated, do not add more than the specified amount
of urine, and do not boil after the urine is added.
{78} _Haines' solution_ is prepared as follows: completely dissolve 30
gr. pure copper sulphate in ½ oz. distilled water, and add ½ oz. pure
glycerin; mix thoroughly, and add 5 oz. liquor potassæ. The solution
keeps well.
(2) Fehling's Test.--Two solutions are required--one containing 34.64
gm. pure crystalline copper sulphate in 500 c.c. distilled water; the
other, 173 gm. Rochelle salt and 100 gm. potassium hydroxid in
500 c.c. distilled water. Mix equal parts of the two solutions in a
test-tube, dilute with 3 or 4 volumes of water, and boil. Add the
urine a little at a time, heating, but not boiling, between additions.
In the presence of glucose a heavy red or yellow precipitate will
appear. The quantity of urine should not exceed that of the reagent.
[Illustration: FIG. 24.--Crystals of phenylglucosazone from diabetic
urine--Kowarsky's test. X500.]
(3) Phenylhydrazin Test.--_Kowarsky's Method_.--In a test-tube take 5
drops pure phenylhydrazin, 10 drops glacial acetic acid, and 1 c.c.
saturated solution of sodium chlorid. A curdy mass results. Add 2 or
3 cc. urine, boil for at least two minutes, and set aside to cool.
Examine the sediment with the microscope, using a two-thirds
objective. If glucose {79} be present, characteristic crystals of
phenylglucosazone will be seen. These are yellow, needle-like crystals
arranged mostly in clusters or in sheaves (Fig. 24). When traces only
of glucose are present, the crystals may not appear for one-half hour
or more. Best crystals are obtained when the fluid is cooled very
slowly. It must not be agitated during cooling.
This is an excellent test for clinical work. It requires slightly more
time than Haines' test, but more than compensates for this by
increased accuracy. It is fully as sensitive as Haines', and has
practically no fallacies excepting levulose, which is a fallacy for
all tests but the polariscope. Other carbohydrates which are capable
of forming crystals with phenylhydrazin are extremely unlikely to do
so when the test is applied directly to the urine by the method just
detailed. Even if not used routinely, this test should always be
resorted to when Haines' test gives a positive reaction in doubtful
cases.
* * * * *
_Quantitative Estimation_.--In quantitative work Fehling's solution,
for so many years the standard, has been largely displaced by Purdy's,
which avoids the heavy precipitate that so greatly obscures the
end-reaction in Fehling's method. The older method is still preferred
by many, and both are, therefore, given. Should the urine contain much
glucose, it must be diluted before making any quantitative test,
allowance being made for the dilution in the subsequent calculation.
Albumin, if present, must be removed by acidifying a considerable
quantity of urine with acetic acid, boiling, and filtering. The
precipitate should then be washed with water and the washings added to
the urine to bring it to its original volume.
* * * * *
(1) Purdy's Method.--Take exactly 35 c.c. of Purdy's solution in a
flask or beaker, add twice its volume of distilled {80} water, heat to
boiling, and, still keeping the solution hot, add the urine very
slowly from a buret until the blue color entirely disappears. Read off
the amount of urine added; considering the strength of Purdy's
solution, it is readily seen that this amount of urine contains 0.02
gm. of glucose, from which the amount in the twenty-four-hour urine,
or the percentage, can easily be calculated. Example: Suppose that
2.5 c.c. of urine discharged the blue color of 35 c.c. of Purdy's
solution. This amount of urine, therefore, contains exactly 0.02 gm.
glucose, and the percentage is obtained from the
equation: 2.5:100 :: 0.02:_x_, and _x_ equals 0.8 per cent. If, then,
the twenty-four-hour quantity of urine were 3000 c.c., the
twenty-four-hour elimination of glucose would be found as follows:
100:3000 :: 0.8:_x_, and _x_ equals 24 gm.
It will be found that after the test is completed the blue color
slowly returns. This is due to reoxidation, and should not be mistaken
for incomplete reduction.
A somewhat simpler application of this method, which is accurate
enough for clinical purposes, is as follows: Take 8¾ c.c. (roughly,
9 c.c.) of Purdy's solution in a large test-tube, dilute with an equal
volume of water, heat to boiling, and, while keeping the solution hot
but not boiling, add the urine drop by drop from a medicine-dropper
until the blue color is entirely gone. Toward the end add the drops
very slowly, not more than 4 or 5 a minute. Divide 10 by the number of
drops required to discharge the blue color; the quotient will be the
percentage of glucose. If 20 drops were required, the percentage would
be 10÷20 = 0.5 per cent. It is imperative that the drops be of such
size that 20 of them will make 1 c.c. Test the dropper with urine, not
water. If the drops are too large, draw out the tip of the dropper; if
too small, file off the tip.
_Purdy's solution_ consists of pure crystalline copper sulphate,
4.752 gm.; potassium hydroxid, 23.5 gm.; ammonia (U.S.P.; sp. gr.,
0.9), 350 c.c.; glycerin, 38 c.c.; distilled water, to make {81}
1000 c.c. Dissolve the copper sulphate and glycerin in 200 c.c. of the
water by aid of gentle heat. In another 200 c.c. of water dissolve the
potassium hydroxid. Mix the two solutions, and when cool, add the
ammonia. Lastly, bring the whole up to 1000 c.c. with distilled water.
This solution is of such strength that the copper in 35 c.c. will be
reduced by exactly 0.02 gm. of glucose.
(2) Fehling's Method.--Take 10 c.c. Fehling's solution (made by mixing
5 c.c. each of the copper and alkaline solutions described on page 78)
in a flask or beaker, add three or four volumes of water, boil, and
add the urine very slowly from a buret until the solution is
completely decolorized, heating but not boiling after each addition.
Fehling's solution is of such strength that the copper in 10 c.c. will
be reduced by exactly 0.05 gm. of glucose. Therefore, the amount of
urine required to decolorize the test solution contains just 0.05 gm.
glucose, and the percentage is easily calculated.
[Illustration: FIG. 25.--Einhorn's saccharimeter.]
(3) Fermentation Method.--This is convenient and satisfactory, its
chief disadvantage being the time required. It {82} depends upon the
fact that glucose is fermented by yeast with evolution of CO_{2}. The
amount of gas evolved is an index of the amount of glucose. Einhorn's
saccharimeter (Fig. 25) is the simplest apparatus.
The urine must be so diluted as to contain not more than 1 per cent.
of glucose. A fragment of fresh yeast cake about the size of a split
pea is mixed with a definite quantity of the urine measured in the
tube which accompanies the apparatus. It should form an emulsion free
from lumps or air-bubbles. The long arm of the apparatus is then
filled with the mixture. At the end of fifteen to twenty-four hours
fermentation will be complete, and the percentage of glucose can be
read off upon the side of the tube. The result must then be multiplied
by the degree of dilution. Since yeast itself sometimes gives off gas,
a control test must be carried out with normal urine and the amount of
gas evolved must be subtracted from that of the test.
* * * * *
(2) Levulose, or fruit-sugar, is very rarely present in the urine
except in association with glucose, and has about the same
significance. Its name is derived from the fact that it rotates
polarized light to the left. It behaves the same as glucose with all
the ordinary tests, and can be distinguished only by polarization.
(3) Lactose, or milk-sugar, is sometimes present in the urine of
nursing women and in that of women who have recently miscarried. It is
of interest chiefly because it may be mistaken for glucose. It reduces
copper, but does not ferment with yeast. In strong solution it can
form crystals with phenylhydrazin, but is extremely unlikely to do so
when the test is applied directly to the urine.
3. Acetone Bodies.--This is a group of closely related
substances--acetone, diacetic acid, and beta-oxybutyric {83} acid.
Acetone is derived from decomposition of diacetic acid, and this in
turn from beta-oxybutyric acid by oxidation. The origin of
beta-oxybutyric acid is not definitely known, but it is probable that
its chief, if not its only, source is in some obscure metabolic
disturbance with abnormal destruction of fats. The three substances
generally appear in the urine in the order mentioned. When the
disturbance is mild, acetone only appears; as it becomes more marked,
diacetic acid is added, and finally beta-oxybutyric acid appears. The
presence of beta-oxybutyric acid in the blood is probably the chief
cause of the form of auto-intoxication known as "acid intoxication."
(1) Acetone.--Minute traces, too small for the ordinary tests, may be
present in the urine under normal conditions. Larger amounts are not
uncommon in fevers, gastrointestinal disturbances, and certain nervous
disorders. Occurrence of acetonuria in pregnancy suggests death of the
fetus.
Acetonuria is practically always observed in acid intoxication, and,
together with diaceturia, constitutes its most significant diagnostic
sign. A similar or identical toxic condition, always accompanied by
acetonuria and often fatal, is now being recognized as a not
infrequent late effect of anesthesia, particularly of chloroform
anesthesia. This postanesthetic toxemia is more likely to appear, and
is more severe when the urine contains any notable amount of acetone
before operation, which suggests the importance of routine examination
for acetone in surgical cases.
Acetone is present in considerable amounts in many cases of diabetes
mellitus, and is always present in severe {84} cases. Its amount is a
better indication of the severity of the disease than is the amount of
sugar. A progressive increase is a grave prognostic sign.
[Illustration: FIG. 26.--A simple distilling apparatus.]
_Detection of Acetone_.--The urine may be tested directly, but it is
best to distil it after adding a little phosphoric or hydrochloric
acid to prevent foaming, and to test the first few cubic centimeters
of distillate. A simple distilling apparatus is shown in Fig. 26. The
test-tube may be attached to the delivery tube by means of a two-hole
rubber cork as shown, the second hole serving as air vent, or, what is
much less satisfactory, it may be tied in place with a string. Should
the vapor not condense well, the test-tube may be immersed in a glass
of cold water.
* * * * *
(1) Gunning's Test.--To a few cubic centimeters of urine or distillate
in a test-tube add a few drops of tincture of iodin {85} and of
ammonia alternately until a heavy black cloud appears. This cloud will
gradually clear up, and if acetone be present, iodoform, usually
crystalline, will separate out. The iodoform can be recognized by its
odor, especially upon heating (there is danger of explosion if the
mixture be heated before the black cloud disappears), or by detection
of the crystals microscopically. The latter, only, is safe, unless one
has an unusually acute sense of smell. Iodoform crystals are
yellowish, six-pointed stars or six-sided plates (Fig. 27).
[Illustration: FIG. 27.--Iodoform crystals obtained in several tests
for acetone by Gunning's method (X about 600).]
This modification of Lieben's test is less sensitive than the
original, but is sufficient for all clinical work; it has the
advantage that alcohol does not cause confusion, and especially that
the sediment of iodoform is practically always crystalline. When
applied directly to the urine, phosphates are precipitated and may
form star-shaped crystals which are very confusing to the
inexperienced.
(2) Lange's Test.--This is a modification of the well-known Legal
test. It is more sensitive and gives a sharper end-reaction. To a
small quantity of urine add about one-twentieth its volume (1 drop for
each 1 c.c.) of glacial acetic acid and a few drops of fresh
concentrated aqueous solution of {86} sodium nitroprussid, and gently
run a little ammonia upon its surface. If acetone be present, a purple
ring will form within a few minutes at the junction of the two fluids.
(3) Trommer's Test.--This new test has proved very satisfactory in the
hands of the writer. The urine need not be distilled. Alkalinize about
10 c.c. of the urine with 2 or 3 c.c. of 40 per cent. caustic soda
solution, add 10 or 12 drops of 10 per cent. alcoholic solution of
salicylous acid (salicyl aldehyd), heat the upper portion nearly to
the boiling-point, and keep at this temperature five minutes or
longer. In the presence of acetone a purplish-red color appears in the
heated portion.
* * * * *
(2) Diacetic acid occurs in the same conditions as acetone, but is
less frequent and has more serious significance. In diabetes its
presence is a grave symptom and often forewarns of approaching coma.
It rarely or never occurs without acetone.
_Detection_.--The urine must be fresh.
* * * * *
(1) Gerhardt's Test.--To a few cubic centimeters of the urine add
solution of ferric chlorid (about 10 per cent.) drop by drop until the
phosphates are precipitated; filter and add more of the ferric
chlorid. If diacetic acid be present, the urine will assume a
Bordeaux-red color which disappears upon boiling. A red or violet
color which does not disappear upon boiling may be produced by other
substances, as phenol, salicylates, and antipyrin.
(2) Lindemann's Test.--To about 10 c.c. of urine add 5 drops 30 per
cent. acetic acid, 5 drops Lugol's solution, and 2 or 3 c.c.
chloroform, and shake. The chloroform does not change color if
diacetic acid be present, but becomes reddish-violet in its absence.
This test is claimed by its advocates to be more sensitive and more
reliable than Gerhardt's.
* * * * *
{87} (3) Oxybutyric acid has much the same significance as diacetic
acid, but is of more serious import. There is no satisfactory clinical
test for it.