Von Noorden and different other au thors regard the tubular epithelium as the unique source of albuminuria. These epithelial cells are subject to successive disintegration: when this is minimal and successive traces, only, of albumin are found in the urine, the albuminuria is physiological; when the decaying of the tubular-epithelial cells is augmented and quickened by disease, a morbid albu minuria takes place. In his opinion, this theory is supported by the fact that micleo-albumin, of which the protoplasm of the cells undoubtedly is the source, is always found in normal urine.
Nucleo-albuminuria always arises from the disintegration of the nuclei of cells that are shed on account of a lesion of the renal epithelium or of an irritation of the vesicle and genito-urinary epithelium. In rare cases it may have an origin. At the same time nucleo albumin should be sought for and esti mated in proportion to the amount of al bumin whenever its presence is suspected. It should not be confounded with muein, which exists in very small quantities in the normal urine. Evano (Gaz. }kb. de MM. et de Chir., Jan. 11, 1900).
From a pathological point of view the causes of albuminuria may be divided into three groups: 1. Disturbances of circulation. 2. Changes of the tubular epithelial cells or of the walls of the blood-vessels of the kidney. 3. Changes in the composition of the blood.
1. All disorders of circulation causing a venous renal congestion will increase the blood-pressure in the capillaries of the kidney, and may thus give rise to a transudation of albuminous liquid; when the congestion is very great the urinary tubules may even be compressed and the escape of the urine rendered difficult. When this is the case and when, also, the supply of arterial blood is dimin ished, the tubular epithelium will be damaged, and the first result of all this is albuminuria. It is improbable that arterial congestion ever produces albuminuria, although the experiments of Munk and Senator tend to prove the contrary.
Functional albuminuria may be re garded as due to vascular changes and as explainable by the mechanical theory. A temporary condition of anoxmmia, whether due to either arterial or venous obstruction, induces albuminuria, through diminished cell-activity and vitality. Results of experiments per formed upon healthy kidneys prove that albumin is secreted by epithelial cells of glomeruli, in capsule of Bowman, and that retardation of blood-current through the vascular plexus of glomeruli is an essential condition; also that anoxiemia of blood-current of the tuft causes al buminuria. J. C. Young (Med. Exam
iner, July, '97).
2. Changes of the tubular epithelia and the walls of blood-vessels of the kid neys may, as already stated, be due to disorders of circulation, but they may also be caused by different poisons and toxins. When albuminuria is chiefly caused by degeneration of the tubular epithelia, their protoplasm dissolves in the urine, and nucleo-albumin in great quantity is contained in it, combined ith serum-albumin and globulin.
Urinalysis of 400 cases of variola, show ing that althuninuria is met with in 95 per cent. of eases, 32 per cent. having abundant albumin. The albuminuria is subject to marked oscillations in amount, and may be absent on certain days. The maximum amount is usually present at the beginning of the febrile period, less commonly during suppuration and desic cation. The albumin often appears in considerable amount when solid food is first taken and when the patient is allowed to get out of bed. Albmnin was present in the urine in 75 per cent. of the cases during convalescence, usually in very small amounts. As a general rule, there was abundant albumin in the se vere cases. There is no such thing as a distinctive albuminuria of convalescenCe. The albuminuria is due to a lesion of the kidneys, this lesion being of either the interstitial form or of the epithelial form. Some chronic lesion of the kidneys prac tically always persists, being, however, extremely slight, as a rule, and causing practically no symptoms. F. Arnaud (Revue de M6(1., May IO, '93).
Albuminuria accompanying lithmmic attacks can only be due to irritation or delicate kidney-structures of child, re sulting from attempt at elimination from blood of poisonous and irritating prod ucts which are causes of attacks. Not infrequently small quan tity of albumin found in infants and children suffering from acute lithmmic attacks. Autointoxication is responsible for this albuminuria either in early or late life. In middle or later life it is due to arteriosclerosis developed by this au tointoxication. Comparative infrequency of lithiemic albuminuria in late child hood and early adult life is due to better developed and more resisting structure of kidney and to the fact that arterial changes found in old lithiemics have not yet had time to develop. Rachford (Pediatrics, July I, '98).