From the standpoint of treatment two varieties of acute nephritis may be recognized. In the one, dropsy is present in addition to marked changes in the composition of the urine. In the other dropsy is absent and unless uraemia or such complications as secondary inflammations develop, the main phenomena presented are the morbid changes in the urine. Although these two forms of nephritis are closely related, the one does not necessarily pass into the other, nor is the one necessarily a less dangerous malady than the other. In some cases of acute nephritis death may result from the severity of the local lesion without the development of any dropsy whatever, and on the other hand, in the dropsical cases, complete subsidence of all the pathological phenomena may take place in the course of time. In all forms of acute nephritis, however, the main indication in dietetic treatment is to diminish to the utmost the work of the kidney. Unfortunately, acute nephritis is of very uncertain duration, and hence the diet cannot be restricted to the full extent desirable for any very prolonged period. There is much to be said in favour of cutting off all food for twenty-four to thirty-six hours at the onset of a really acute nephritis unless this complication occurs in the course of some infective disease where the general strength of the patient has already been much diminished, and where it is not desirable therefore to further weaken him. In many cases the restriction to this extreme extent is not difficult owing to the great distaste for food and the presence of considerable nausea and vomiting. Such patients should simply be allowed water in moderate amount during the twenty-four or thirty-six hours during which the food is stopped. The bulk of cases of so-called acute nephritis are not of a sufficiently severe type to require this treatment, which is really mainly indicated in those severe cases of acute nephritis which are ushered in with almost complete suppression or, at any rate, with the secretion of a very scanty highly blood-stained urine. Although the water is beneficial from the point of view of flushing out the kidney and getting rid of the detritus, care must be taken not to administer it in excessive amount, as it is precisely in this form of acute nephritis that the excretion of water by the kidney is most seriously compromised. In cases of acute nephritis where dropsy is present and where usually the suppression of urine is not developed to such a high degree as in the first type of case, there is not the same necessity for cutting off all food. The diminution in the excretion of urine in the dropsical type of case is, in part, dependent on the development of the dropsy, and although no doubt the excretory activity of the kidney is more or less seriously impaired, yet it is not so extensively affected as in the first type of case.
In the anasarcous variety of acute nephritis and in the other less severe cases of acute nephritis, the diet should consist essentially of milk. It is desirable, however, not to give this in large quantities as it is essential to maintain the principle of cutting down the work of the kidney to as great an extent as possible. Three pints of milk per diem is probably about the minimum amount required by a normal adult, and even on this quantity it is impossible to maintain normal nutrition for any prolonged period. In acute nephritis, however, far smaller quantities than this may be given, at any rate for a time, as no great harm will result from a temporary cutting down of the diet below the normal quantity required. Hence the diet may be restricted with advantage to one pint or one pint and a half of milk in the twenty-four hours. In many cases there is such distaste for food and so much nausea that there is no advantage in attempting to increase the quantity or the kind of food given; but in others where these symptoms are not marked there can be no harm in giving food-stuffs such as carbo-hydrates and even fats which do not increase to any material extent the work of the kidney. Thus there is much to be said in favour of diluting the milk with barley-water or gruel, or even if the patient desires it allowing bread and butter in small quantities. Better results will be obtained by giving a moderate quantity of milk with the addition of small quantities of bread or of bread and butter than by increasing simply the quantity of milk. In those cases where dropsy is marked and where there is only diminution in the amount of urine rather than actual suppression some departure from the milk diet may be advisable, and such patients may take larger quantities of bread and butter, or even vegetable food, such as mashed potato, if they have sufficient appetite or desire and taste for such food. Several observers have obtained good results in the treatment of acute nephritis by giving a relatively dry diet of this type than by the indiscriminate administration of milk. Better results still are obtained if salt is entirely eliminated from the food. This, however, is difficult as it involves the necessity of special methods of preparation as, for example, production of a salt-free bread and the restriction of salt in the food is perhaps of more importance in the treatment of chronic than in the treatment of acute renal disease.
In all cases where the food given is fluid, as for example, milk and gruel, care should be taken that the total amount of fluid given in the twenty-four hours is not unduly large in cases where there is obvious difficulty in the excretion of water as shown either by the state of the urine, or by the presence of dropsy. Various fruits may be given even in acute renal disease, as very often they will give much relief by obviating thirst and by relieving the unpleasant taste in the mouth that is so often associated with the different forms of acute and chronic renal disease. Fruit juices are also of considerable nutritive value, and although many fruits contain diuretic substances it is not probable that these will produce any injurious effect in the small quantities that are likely to be taken in the course of such a malady as acute nephritis. The juice obtained from pine-apples, peaches, grapes, oranges, grape-fruit, are all useful. On the other hand, meat extracts, animal broths, beef-tea, should not be given. The nutritive value of many of these is very low unless they are made in such a fashion as to retain the protein constituents of the flesh, and if this be done there is no class of food-stuff that is more unsuitable for the treatment of acute renal disease. Such extracts are always rich in nitrogenous extractives and salts and as already stated, may contain considerable quantities of protein; thus they greatly increase the work of the kidney and should on no account be allowed.
Patients often object to milk, more especially on account of the nausea that is such a constant feature in renal disease and further, in many instances, vomiting may also be present. If these symptoms are marked it would probably be advisable to partially digest the milk prior to its administration, and the best results are frequently obtained by pancreatizing a mixture of equal parts of milk and gruel.
Alcohol should not be given in acute renal disease unless there is urgent need for its administration owing to the development of some complication requiring cardiac stimulation.
With the subsidence of a nephritis the diet can be gradually increased in amount and more solid food in the form of bread and butter, bread and milk, milk puddings, can be given.