Causes

Interstitial nephritis is due either to arterio-fibrosis and consequent destructive anemia of minute areas of renal tissue, or to toxins that, acting intermittently over long periods of time, similarly destroy minute areas of tissue successively. The toxins commonly may be inorganic salts, or those producing what is called the uric acid diathesis. Generous, one might almost say gluttonous, eating of rich foods, especially beef, mutton, and game, with rich gravies, sauces, and soups, drinking small quantities of fluid, unless it be alcoholic beverages, and a sedentary life are the factors usually producing this diathesis; but in some persons of abstemious habits it may appear as an inheritance. Hard work, physical or mental and hearty eating are important causes of atheroma and arteriosclerotic changes, which frequently produce the local anemias in the kidney that cause this lesion. It is therefore evident that indiscretions in diet play an important part in producing contracted kidney.

Treatment

Interstitial nephritis is so chronic a disease that an exclusive milk diet, even if it were necessary, could be maintained only for a small part of its entire course. The observations of Zasiadko, of St. Petersburg, are suggestive of the value of different diets in chronic nephritis. He administered to ten patients suffering from chronic nephritis a vegetable diet for ten days; for a like period, an animal diet, with a little bread added; and for another equal period of time, a mixed diet. While upon a vegetable diet the amount of albumin in the urine increased, arterial tension diminished, dropsy increased, the pulse became slower, weaker, and softer, appetite failed, and the patient became weaker and more apathetic; while upon animal food, albumin increased in the urine, arterial tension rose, edema lessened, the pulse quickened and grew fuller, and the patients became stronger and more cheerful. The effects of a mixed diet were midway between these.

The best foods for patients with contracted kidneys must be determined to some extent by trial in each case. Disturbances of digestion must also guide the physician in making a dietetic prescription. A mixed diet is safest except when the urine is much diminished by acute exacerbations of the nephritis. A milk diet for a time is then needed. It is also needed in the last stage of the illness when the heart grows weak and the pulse soft. In this disease uremia, in mild or severe form, frequently occurs, and it also is an indication for the exclusive use of milk or temporary abstinence from food (see Uremia).

Under other circumstances than these the diet maybe varied and mixed. Food should, however, be eaten abstemiously. The greatest care should be taken to prevent overtaxing the digestive organs, or permitting an accumulation of food or of its detritus in the alimentary canal. An abstemious diet, such as can be permitted, is not natural to most who suffer from this disease. They are usually high livers, fond of the richest foods, and of generous quantities of them. It is safest for such patients to eschew meat soups, beef-extracts, red meats, game, crustaceans, and cheese. With the exception of milk, which should form an important element of diet, it is best for them to use even the simplest animal food in small quantities. In this disease meat foods possess the same relative toxicity as in diffuse nephitis. If the condition of digestion will permit, fats, cream, butter, and farinaceous foods should be eaten freely.

In order to prolong, as much as possible, the life of a patient suffering from this disease, every care must be taken to prevent, or to correct, indigestion, and to maintain a copious flow of urine. When a mixed diet is permitted, water should be drunk copiously. At least two quarts of liquid should be taken daily. Water is the best beverage, and a water that contains little or no mineral matter is to be preferred. Tea, coffee, cocoa, or chocolate may be used in moderation, provided digestion is good. They must not, however, be permitted to lessen the amount of fluid drunk daily. Those who are most prone to this ailment are inclined to drink little, and what they prefer to drink is apt to disturb digestion or the action of the kidneys more or less. A cup of tea or coffee at each meal or wine or beer is all that they crave. Such patients must be taught to drink water freely. If permitting them to drink tea or coffee leads them, as it often does, to take less water than they should, those beverages must be forbidden.

The following will illustrate a suitable menu for a day for one having interstitial nephritis without digestive disorders or other complications:

Breakfast

A glass of milk or cup of coffee, a small dish of cereal, one egg, one slice of bread and butter, fruit.

Lunch

A glass of milk, a small portion of asparagus or peas or string beans, one or two slices of bread with butter, fruit, fresh or stewed.

Dinner

About one-half of an ordinary portion of chicken, one potato, a small portion of cauliflower or other green vegetable, lettuce or tomato salad, a slice of bread and butter, a small portion of pudding or ice-cream or fruit.

The patient can be instructed generally with advantage to drink a glass of water on first arising in the morning and about 10 A.M., 3 and 9 P.M.

As a rule blood tension is high in this disease and it frequently causes appoplexy and hemiplegia by rupturing diseased cerebral arteries. The high tension can often be lowered and the safety of the patient thereby increased by from time to time resorting to purgation and a most simple and abstemious diet, such as a modicum of milk, six or at most eight glasses daily, and fruit. In a few days bread and cereals may be added and later the usual mixed diet may be resumed. Relief of the gastrointestinal tract effected by this diet, diminution of toxins ordinarily generated therein, and to a less extent diminution of the quantity of fluid passed through the blood vessels, lowers arterial pressure. The ill effects of high pressure and the increased danger of fatal accidents from it will be lessened at all times by preventing constipation and much fermentation of food in the gastrointestinal tract.

By all clinicians alcoholic beverages are forbidden in renal affections because they are renal irritants, although they vary in toxicity, chiefly according as the proportion of alcohol that they contain varies.

A permanent residence in a genial and equable climate is especially desirable for those affected with chronic interstitial nephritis. The same care to maintain a free action of the skin by friction and by bathing is desirable in these cases as in diffuse nephritis. Hot baths must be taken with caution when there is much atheroma of arteries. Regular daily exercise should be encouraged, but it should never be exhausting or even very fatiguing. Occasional residence at spas is of benefit. What has already been said of their value and applicability in diffuse nephritis might be repeated here.