This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Temporary functional albuminuria is now recognised as occurring in many individuals without the significance of any structural or organic lesion of the kidney. This subject has been exhaustively investigated by the medical examiners of life-insurance companies, for it is of great importance not only to discover the presence of albuminuria early, but to assign the proper significance to its presence. It is not many years since the detection of albumin in the urine was regarded as an infallible indication of some form of renal disease, but the fact is now established that errors in diet and faulty assimilation produced by mental and nervous strain, overwork, and worry, and more particularly by the exhaustion of very rapid growth of the body in the later years of childhood and early youth, may occasion albuminuria.
A solution of meat albumin experimentally transfused into the venous circulation of a dog, injected either subcutaneously or into the rectum, reappears unaltered in the urine, but serum albumin similarly injected is retained by the blood and does not cause albuminuria, although the percentage of albumin in the blood plasma has been considerably raised above the normal. Moreover, if a man in health eats eight or ten raw eggs in the course of five or six hours, traces of serum (not egg) albumin may appear in the urine. The matter is of interest in connection with the diet for chronic Bright's disease (p. 505). Albuminuria thus produced is purely temporary, and is directly dependent on the nature of the food. So much of this proteid has been eaten that a portion of it is absorbed directly into the blood without the formation of intermediate products of digestion. Similarly this albumin will osmose through the kidney. But if the digestive activity in the stomach is very great, a large number of raw eggs may be eaten, and as many as nineteen have been taken in thirty-six hours (Dolradin) without the appearance of albuminuria.
It is no doubt true in such an instance, as suggested by Yeo, that the vigour of the digestion converts egg albumin into peptones, which finally form serum albumin, whereas with a slower digestion more of the egg albumin is absorbed unaltered.
According to the experiments of Stokvis, coagulated egg albumin cannot be made to reappear in the urine of healthy animals, but raw egg albumin can.
Oertel (Therapeutics of Circulatory Derangements, in von Ziems-sen's Handbook of General Therapeutics), as a result of numerous experiments upon man and animals in opposition to the above view, declares that "egg albumin, given in whatever quantity, is not normally excreted as such by the kidneys, and does not cause albuminuria." The albumin absorbed is all destroyed in the blood or tissues and excreted as urea from the kidneys. He further says that "a great increase of albumin supplied to the blood causes no increased excretion of albumin by the kidneys, and, in particular, that egg albumin gives rise to no irritation of the renal vessels and no albuminuria (nor does it increase an existing albuminuria)".
This statement, if corroborated by further observation, would considerably alter the prevailing notions in regard to the advisability of giving eggs to patients with chronic Bright's disease.
Of all the varieties of albuminuria, those which are most amenable to dietetic treatment are the functional form and that which accompanies chronic Bright's disease. The functional albuminuria which is produced by eating an excess of protein or by muscular fatigue, which results in the accumulation of large quantities of nitrogenous waste matter and interference with normal oxidation processes, is usually curable by ascertaining and removing the cause.
It seems to be almost impossible to produce functional albuminuria in the lower animals, such as dogs, by overfeeding them with a very large excess of albuminous food. Voit caused a dog to absorb within twenty-four hours six times the amount of albumin contained in the blood plasma without exciting albuminuria.
In the instance given above of albuminuria caused by eating large numbers of eggs, it was emphasised that the proteid in the urine is egg albumin and not serum albumin. It is stated, however, that occasionally serum albuminuria may be produced in man by eating large quantities of meat. If true, this is certainly very unusual, and this form of albuminuria is by no means as readily induced as the glycosuria caused by an excess of starches in the food. But if albuminuria already exists, certain forms of nitrogenous food will greatly increase the amount eliminated by the kidneys.
It is probable that some persons inherit a special weakness of the kidney structure or an abnormal irritability of the renal cells which favours the occurrence of albuminuria from slight provocation. Granger Stewart (Lectures on Important Symptoms of Albuminuria) states that he has observed in certain persons that cheese, pastry, and eggs are substances capable of producing temporary albuminuria. In one case this symptom was accompanied by oedema of the eyelids.
In regard to the production of functional albuminuria from dietetic errors Yeo argues, and I think correctly, as follows: " May not the true explanation be that the ingestion of so large an excess of albuminous material may throw upon the kidneys such an excess of nitrogenous waste (to be secreted) that a temporary functional hyperemia of the kidneys is excited, and that this leads to a slight escape of albumin from the blood? It appears to us that this is a sound physiological explanation of what is observed to occur, and accounts for its occurrence in fever or disordered constitution, and not in the perfectly sound and vigorous".
Albuminuria also results from passive hyperaemia of the vessels of the kidney, as well as from active congestion and inflammation.
In functional albuminuria, when traces of serum albumin appear from time to time in the urine, it is found that the amount is proportionately increased by any special fatigue or exhaustion. It is possible, although it is by no means proved, that nerve currents supplying the epithelial cells of the renal tubules or the walls of the renal capillaries may cause a functional alteration in the activity of these cells, which compels them to exercise a selective action upon the albumin of the blood serum, and favours its osmosis. The theory is advanced by Mills, of Montreal, that the epithelium of the capillaries possesses some at least of the functions of glandular epithelium, and that it is capable of controlling and varying the quality as well as the quantity of such substances as may pass through the minute capillary walls.
Albuminuria is very common as a result of elimination of irritant poisons from the kidneys, and it is believed that the albuminuria usually present in diphtheria and the exanthemata is produced by 34 the irritant effect upon the kidneys of toxins developed in these diseases which are being eliminated in the urine.
The frequent return of functional albuminuria should be regarded as an indication of special weakness of the kidneys in the same way that frequent glycosuria invites suspicion of the strength of the digestive power of the liver, and it demands a careful regulation of the diet. Meat should be reduced in quantity, or temporarily forbidden, as well as all forms of alcoholic drinks or other substances liable to produce renal irritation, and the diet should consist chiefly of fruits, vegetables, and milk. Careful attention must be paid to increasing the activity of the bowels. When functional albuminuria is observed in children and adolescents, it is not necessary, nor is it advisable in ordinary cases, to wholly exclude nitrogenous food, but it should be restricted, especially in regard to eating butcher's meat and eggs, and the evening meal should be made very simple, consisting of food such as bread, crackers, rice or porridge, and milk.