Variations occur not only in the quantity of water passed from the kid neys, but also in the amount of solid matters excreted. Thus, in febrile diseases the urine is not only more concentrated from deficiency of water, but it is richer in urea and uric acid, although poorer in chlorides. In health the quantity of urea passed by a child is relatively greater than it is in the adult. According to TJhle, children between three and six years of age pass in the twenty-four hours one gramme of urea for each kilogramme of their weight. This fact is important as indicating the active metamorpho sis of the protein compounds of the body which occurs in early life.
It has been said that the water of a young child in perfect health is quite clear. In the normal state it is also slightly acid. Very slight causes will give rise to an increase in the amount of acid secreted, and the water is then apt to be thick with lithates. As in older persons, the turbidity generally occurs as the urine cools on standing ; but sometimes it is turbid while still warm, and may even be passed thick from the bladder. Infants, especially, sometimes alarm their mothers by voiding water thick and milky-looking from a profuse secretion of urate of soda. The appearance of a deposit of lithates may be due to two causes :—To increased secretion of the salts, and to excess of acid in the water. Young children who are habitually overfed continually pass water loaded with 'Abates ; and if they are taking inordinate quantities of fermentable material in their food, the amount of acid is also greater than normal. Thus, both the causes which conduce to turbidity of urine are present. During convalescence from acute disease in a child, when it is our object to further the return of flesh and strength by an ample supply of nourishing food, and at the same time to avoid overburdening the digestive organs by an excess of nutritive ma terial, the state of the water offers a very good index as to whether the necessary quantity has been exceeded. If the child is eating too much, his water becomes at once thick with lithates, and warns us to make some reduction in the quantity, or alteration in the quality of his meals.
Besides lithates, young children, and even infants, may pass free uric acid in their water. This subject will be considered afterwards (see Cal culus of Kidney).
The urine in infants is sometimes noticed to be very offensive. This is, due to a catarrhal condition of the bladder, and denotes rapid decomposi tion of the urea. Another symptom sometimes complained of by the mother is that the water is very dark in colour and causes stains on the diaper. This may be the consequence of the presence of bile-pigment in the urine.
Albumen is often found in the urine of children, but must not be looked upon as in every case indicating disease of the kidneys. It is seen in many inflammatory complaints and fevers, as in pneumonia, diphtheria, measles, typhoid fever, etc. In such cases it is probably dependent either upon an altered condition of the blood, when it is an expression of the general disturbance of the system induced by the illness, or upon an in fectious nephritis, which is found, according to H. Bouchard, in many
forms of acute specific fever. Again, a casual admixture of blood or pus with the urine may give rise to the presence of albumen, as in cases of ir ritation of the urinary passages by calculous concretions. Passive conges tion of the kidneys, such as takes place in many cases of heart disease and in some forms of bronchitis, may be a cause of the same symptom, and the albumen may be accompanied by epithelial and blood casts. But in these cases the presence of the albumen, and even of the casts, is no indication of organic disease of the kidneys. We are only justified in inferring the existence of renal disease when we find by the microscope hyaline or granular casts in conjunction with the albuminuria. A transient albuminuria is sometimes met with, and appears to be a result of some bodily derangement quite independent of renal disease. It may be found in school-boys who are preparing for examination. Dr. Kinnicutt at tributes it in many cases to a transient oxaluria or lithuria. It has also been seen in ague districts as a consequence of malaria. Intermittent al buminuria—albumen being abundant one day, absent the next—is usually due to an admixture of secretions, and should lead us to suspect a habit of masturbation.
As in older persons; the urine of children and even of infants may con tain blood. This may be poured out from any part of the urinary passages. When the source of the blood is the urethra or bladder, the two fluids are passed separately without mingling together. Thus, in a case of vesical calculus, the child passes first water and then a little blood from the bladder. When the two fluids are intimately blended, we are justified in concluding that the blood comes from the kidney. Renal hemorrhage is not very uncommon in young subjects, and may occur in large or in small quantity. When in large quantity—in quantity sufficient to give a dark red colour to the whole volume of urine—the blood may be usually ascribed to one of two causes ; either to hmorrhagic purpura, or to irritation of the kidney by calculous concretions. In the first case there are signs of haemorrhage from other mucous passages and into the skin. In the second, the child may complain of no pain, and appear, except for the hemorrhage, to be perfectly well. In smaller quantities, often enough merely to give a smoky tint to the urine, hmmaturia is seen in acute Bright's disease, in hemorrhagic measles, in scarlatina, diphtheria, and small-pox ; sometimes, also, in ague. Even after suppression of urine in children suffering from inflammatory diarrhoea, the renal secretion, when the function of the kidneys is restored, may contain blood. In fact, wherever albumen is present in the urine blood may be present as well. In all such cases the blood-corpuscles may be recognized by the microscope. Occasionally, es pecially in scarlatina before the appearance of albuminuria, the urine 'may contain the colouring matter of the blood, but without any of the corpuscles being discovered by microscopical examination.