The most rational hygiene of the kidneys for the prevention of kidney diseases consists in the avoidance of all those causes which are injurious to the kidneys, and which we have mentioned in the previous chapter. A great part of the poisonous products that are eliminated by the kidneys are introduced with the food and beverages, and it is important for us to bear in mind the fact that what we eat or drink must pass through our kidneys, and that the structure of these organs is delicate; that the most important secreting parts are composed of fine epithelium which can easily be desquamated by the passage of irritating products. Thus we note the appearance of hyaline casts after different kinds of spices and stimulating liquors, especially if taken in large quantities.
There are many members of the profession who attach no importance to the occasional appearance of a hyaline cast. But, considering the finding of Professor Senator[225] that such casts are formed by degeneration of the tubular epithelium, we cannot take such a lenient view; for even if we find only one cast in two or three microscopic specimens, we must realize how many thousands of these there may be in a liter of urine. Thus every day thousands of these casts, and in a year enormous quantities, may be lost. But as each cast means the loss of important secreting elements, there can be no doubt that, after a certain time, we shall have lost an important part of these most important organs, whose place is taken by connective tissue. Thus the development of interstitial nephritis can be hastened by faults in our alimentary régime. In cases where meat is taken abundantly it is most probable that the continual excretion from the blood of nitrogenous end-products of metabolism means a serious overwork for the kidneys and grave damage to their epithelium. And still more so if, owing to a diminished activity of the liver due to senile degeneration, toxic products of a higher toxicity than urea, and even uric acid, are passed.
We have observed the great frequency of albuminuria and casts in the urine of persons who were addicted for many years to a plentiful meat diet. According to Dr. James Tyson,[226] who has been for many years making accurate observations on diseases of the kidneys, and who has published a standard work on them, interstitial nephritis can be produced after the prolonged ingestion of much meat. If we wish to keep our kidneys in the best condition, a lacto-vegetarian diet with only little meat, once a day, is the most suitable. Still more than meat, bouillon and meat gravies should be avoided, since they contain irritating meat extracts.
Milk diet in abundance is not only indicated in liver disease, but also in chronic kidney troubles. But when there are coexisting changes in the circulatory system, milk should not be given in large quantities, but in smaller amounts. Milk has also the great advantage of being a strongly diuretic substance, especially in its acidulated forms (yogurth or kefyr, or simple sour milk); and at the same time it irritates the kidneys very little, since it contains only a minute amount of common salt.
According to Bunge, we take decidedly too much salt every day, and in this way we injure our kidneys considerably. Achard,[227] Strauss,[228] Vidal and Javal,[229] and simultaneously H. Strauss, have found that diseased kidneys (especially in acute or chronic parenchymatous inflammations) are unable to eliminate sodium chloride properly, and its retention leads to œdema. According to these authorities, œdema is caused by a retention of water and sodium chloride, the retention of the latter playing the primary rôle, whereas according to Alexander Koranyi, Richter, Kovesi, and Roth-Schulz, the retention of the water is the primary factor.
For these reasons salt should only be taken in very small quantities. Alcohol should also be avoided, except in small quantities, as being very injurious to the kidneys; and considering that chronic nephritis may be caused by the immoderate use of alcohol, Bunge thinks that the chronic nephritis following large quantities of alcohol may be attributed to the fact that, according to the researches of Keller,[230] made in Bunge’s laboratory, the alcohol habit leads to an immoderate use of salt with its deleterious effects upon the kidneys.
According to Bunge, rice gives very little work to the kidneys, as in twenty-four hours only 2 grammes of alkaline salts are eliminated. On the other hand, potatoes cause a very great elimination of salt by the kidneys. Bunge thinks that rice would be a good food for patients with renal disease.
Not only alcohol, but other stimulants, like tea, can be of harm to the kidneys if taken in large quantities, as we have mentioned in the preceding chapter when speaking of black tea.
We do not think, however, that the daily use of black tea, in moderate quantities, would have unfavorable effects on the kidneys. Its relation to the production of uric acid should, however, be remembered (see chapter on other stimulants: coffee, tea, tobacco, etc.).
For reasons already mentioned, irritating spices and adulterated sauces should be very carefully avoided; also all kinds of food which contain pungent ingredients. We have no doubt that by their use life is often shortened. The passage of such poisonous substances for years through our kidneys must injure their delicate structure and hasten the development of the senile kidneys, with interstitial nephritis.
It is advisable to drink plenty of water, especially when much meat, or the above-mentioned sauces, are eaten. By this means we can flush out of our kidneys the end-products of proteid food, and also other toxic substances. For the same reason it is well to use certain mineral waters with diuretic properties. They should, however, not be taken at the same moment as substances irritating to the kidneys are taken, or the kidneys may be so injured that acute hæmorrhagic nephritis may ensue. We[231] have published such a case, where even small quantities of chloride of potassium taken on an empty stomach, together with Wildungen waters, which have very diuretic properties, provoked a condition of acute nephritis, with great quantities of blood clots, epithelial and granular casts, many epithelial cells, and red and white blood-corpuscles in the urine.
When taking various drugs, we must always remember that they must pass through our kidneys. The drug habit, especially when irritating drugs are taken, can have a ruinous effect on these vital organs and surely diminish our prospects for a long life. Day by day many of the epithelial cells will be desquamated, slowly but surely, and inflammatory conditions of the kidneys will eventually appear. There is nothing in this world without a cause, and if a chronic parenchymatous or interstitial nephritis suddenly appear, it must have a pre-existing cause. It is the result of our continual neglect and abuse of these most important organs. As Prof. Friedlich Müller said a few years ago, the kidneys never forget the wrong they once have suffered. Indeed, most of the evil that befalls us in this world is our own fault, for doing things we should not do and omitting those we should.
A frequent source of renal diseases is infectious diseases with the passage of toxic products through the kidneys. This source of kidney disease is often overlooked, the symptoms of acute nephritis being mistaken for or confused with those of the infectious disease. Acute nephritis after tonsillitis is often not diagnosed unless the symptoms are very marked. In such cases occasional casts and epithelial cells, with red and white blood-corpuscles, may remain for a long time in the urine, sometimes permanently, and thus slowly and insidiously chronic nephritis develops.
Tonsillitis is often caused by the dropping upon the tonsils of mucous secretion from a post-nasal catarrh. This is commonly so in chronic rhinitis caused by adenoid vegetations. The best prevention of renal diseases in these cases is operation on the vegetations and treatment of the rhinitis, rather than removal of the tonsils, which probably play a great rôle in the defense of the organism against infections. This is shown by the fact that they are inflamed in the early stages of many infectious diseases.
The greatest care must be given to the condition of the skin and intestines, if we wish to keep our kidneys in good order and prevent their deterioration. We must try to eliminate through the skin and intestines as many as possible of the toxic substances which otherwise would make their way to the kidneys and increase their work, and perhaps injure their epithelium. In this way we can save our kidneys for their time of need.
Therefore, the skin and intestines should be kept in good working order. We must do all we can to maintain the function of the skin, and in several chapters of this book we have considered this question. We will only mention briefly that the invisible perspiration of the skin should be encouraged as much as possible. Damp and cold weather are apt to suppress it. In such weather our skin also gives off too much warmth, therefore we should be warmly clad, wool, especially for old persons, being best. Still more important is this when the kidneys are already damaged. For such persons a warn climate is advisable. By increasing the perspiration to sweating, products which are harmful to the kidneys may be eliminated. Hence such procedures will take work off the kidneys and rid them of injurious substances. The sweating should be done frequently, at least once a week, if we want to keep our kidneys in good condition. For fuller particulars on the hygiene of the skin, and also of the intestines, we refer to the chapters relative to these questions.