THE PHYSIOLOGY AND PATHOLOGY OF THE URINE Daily quantity.—During the first three or four days of life the secre tion of urine is extremely small. This is not by any means solely due to the lack of nourishment, for babies suckled by a nurse and artificially fed infants, both of whom receive relatively plenty of liquid, behave exactly the same as those who are nursed at the mother's breast. The considerable individual variations in the urinary secretion during the first days of life, as shown in the comparative table of Reusing, are remarkable.
In comparing the quantity of the urine and the quantity of nutri ment, and in computing the proportion of the percentage, we find that the sucking babe has no continuous increase in the daily quantity, but tolerably irregular variations. It seems pretty well established that the nursling during its first days of life secretes relatively little of the water introduced, while thc quantity of the urine of the artificially fed babe attains both absolutely ancl relatively high quantities. This will be illustrated by the figures given by Reusing.
But even in the artificially nourished babe, the increase of urinary secretion does not exactly correspond to the increased supply of food.
Premature infants secrete minimal quantities of urine, but we do not have many subjects. In the later months of the first year, for the healthy babe the law becomes valid that 100 Gm. of nourishment produce 68 c.c. of urinary secretion. This law was discovered by Cam ercr, and confirmed by Czerny and Keller. In regard to the quantities of urine secreted by healthy infants after the first year, Camerer has fully informed us by exact examinations conducted through mauy years.
They show that the increase in the quantity of the urine is not exactly in proportion to the nutritive supply, but lags behind it. It is of course not possible to formulate a rule for the quantity of urine at every stage of life: a mixed diet, as well as individual peculiarities, will cause a variation in the proportions. The table prepared by IIolt which takes cognizance of the examinations of Schabanowa, Cruse, Camerer, Pollack, illartin-Ruge, Berti, Schiff, and Herter, has therefore only a relative value. According to Holt the daily quantities of urine arc: In the first 24 hours up to GO In the second 24 hums 10-90 From third to 6th day 90-250 From 7th day to 2 ms 1.50-400 From 2 ms. to fith month 210-500 From fith month to 2nd year 250-600 From 2nd to 5th year 500—S00 From 5th to Sth year 600-1200 From Sth to 14th year 1000-1500 -Very different pathological conditions produce changes in the quan tity of the urine. It must therefore be most emphatically stated that the observations of Camerer are valid only for the healthy child, and even slight disturbances may change the proportion between the quan tity of urine and the quantity of nutriment. Granular atrophy (con tracted kidney), diabetes mellitus and insipidus, which may begin even in the nursling, will result in the excretion of especially large quantities of urine. It may de very difficult to establish by uranalysis the dif ference between granular atrophy (contracted kidney) and diabetes insipidus. Hypersecretion and low specific gravity are characteristic! of both diseases, and renal casts may be equally lacking in the contracted kidney during infancy.
Frequency of Urination.—In the newborn the bladder is emptied as a rule immediately after delivery (Bendix). The younger the child, the oftener the bladder is emptied, but it is possible by training to bring about an early control over the sphincter. According to Holt a child of two years can retain its urine for from 2-6 hours during sleep; a normal child of three years may sleep for S to 9 Flours without wetting itself, and while awake may retain the urine for intervals of 2 to 3 hours.
Physical Properties.—The color of the urine of healthy infants is generally a pale straw-yellow, perhaps a little more intense up to the sixth to tenth day, but still lighter in color than the urine of adults. The concentration (or specific gravity) generally influences the depth of the color. The reaction of the urine is strongly acid during the first fen- days, especially, according to Flensburg, during the period of inward infarction. The urine of the newborn either does not normally turn the plane of polarized light to the left, or else does so quite feebly. Ac cording to ('zerny and T:eller, the specific gravity of the healthy infant varies according to the state of nutrition, from 1.011 to 1.012. "As soon as the supply of liquid and the excretion of the urine have reached the normal quantity, the specific gravity sinks to 1.003-1.004, and remains at this level till the end of the first year." Holt gives the following summary of the specific gravity at the vari ous periods of life:— 1st-3rd day 1 010-1.012 4th-lOth day 1 001-1.00S 10th day-Oth month 1 004-1.010 6th month-2nd year 1 006-1 012 2nd-Sth year 100S-1.016 Sth-14th year 1 002-1.020 High specific gravity as a rule is associated with scanty secretion of urine; low specific gravity with abundant flow of water, and if an unusual quantity of urine is combined with a high specific gravity, the suspicion should at once arise that diabetes mellitus may be present, which is not so rare during infancy as many have supposed. On the other hand, the combination for a considerable time of a large quantity with low specific gravity, must arouse the suspicion of beginning renal disorder, since it is well known that in such a disorder the capacity of the kidney to concentrate the urine is the first thing to suffer.
The osmotic analysis has not up to this time acquired either great theoretical or practical importance in pediatrics. The comprehensive examination of Sommerfeld and Roder have shown that the freezing point of the urine is lower in babies than it is in adults, but that it varies between tolerably wide limits according to the method of feeding. The variations are widest in breast-fed babies. The values of the urine of infants must be considered extraordinarily high in comparison with the amount of crystalline matter. Roder and Sommeifeld leave the question open whether the appearance of dissociation is the im portant factor, or whether the high value is to be attributed to the presence of ether, and as yet unrecognized substances. This problem can only be determined by an electrolytic examination. In the infec tious diseases, which are often complicated by renal disease, the lowering of the freezing point, and the molecular concentration permit us, even before pathological elements are capable of demonstration, to suspect the beginning of darnage to the kidney (Labb6).
The urine voided immediately after birth, is, according to Flens burg, almost clear. Specimens passed later than this are generally turbid, and this condition will continue till the eleventh day. But if the urine does not become clear after the tenth day, we should suspect the presence of some pathological condition. The turbidness is present in urine containing infarcts, as well as in specimens free from uric acid. In the former there are found, according to some authors, not only uric acid and uric aeid salts, but also hyaline and epithelial casts. The question as to whether casts appear in the physiological urine of the newborn or not is still undecided.