ALBUMINURIA. — From Lat., albu min; and Gr., oupEtr, to pass the urine.
Definition.—The presence of albumin in the urine. Albuminuria may be true —when the albumin is dissolved in the urine—or spurious, when caused by ad mixture of semen, pus, or blood in the urine. Spurious albuminuria is easily distinguished from the true form by the aid of the microscope. Both kinds of albuminuria may occur simultaneously.
Domenico Botugno discovered, in 1770, that urine may contain albumin; by boiling a sample of urine he found that pure albumin was precipitated. It was long maintained by all authors that albuminuria has always been a symptom of disease, but of late many authorities have admitted that albuminuria may be compatible with perfect health.
Posner maintains that albumin is always found in the urine, but normally in too small quantity to be revealed by the ordinary reagents. To demonstrate the presence of albumin in normal urine Posner evaporated large quantities of urine at low temperature and tried the different reagents in the concentrated urine. His experiences have been re peated and his views supported by Senator and by Leube, who, however, did not find albumin in all cases. Von Noord en, Winternitz, Lecorche, Tala mon, and different other authors do not admit that albumin is a constituent of the normal urine. At any rate, only traces of albumin can be considered as physiological.
Different kinds of albumin may be present in the urine; generally the pro teids contained in the blood-serum are to be found,—viz.: (1) the serum-albu min, or serin, and (2) the globulin, or paraglobulin; in most cases both these proteids are present, but in varying pro portions. In some cases there may also be found (3) hemialbumose, or propep ton, a mixture of different albumoses which are not precipitated by boiling; (4) nucleo-albumin, which has also er roneously been called "mucin"; and (5) pepton.
Five proteids are found in the urine, viz.: (1) serum-albumin; (2) serum globulin; (3) nucleo-albumin, or mucin; (4) pepton; (5) albumose, or propep ton. The first two are of special im portance because of their association with nephritis. Mucin is usually present normally in small amount in the urine.
Pepton and albumose should never ap pear in normal urine. Serum-albumin in the urine may be due to (1) renal disease or (2) to the pressure of pus, spermatozoa, blood, or elements of tumors. Urine containing these sub stances will give the albumin-reaction.
Renal albuminuria may be divided etiologically into (1) that following cer tain febrile diseases; (2) nervous albu minuria, following some diseases of the central nervous system; (3) htemato genetic albuminuria; (4) toxic albu minuria; (5) albuminuria of pregnancy; (6) congestive albuminuria ; (7) albu minuria due to long-continued exposure. The appearance of pepton in the urine is pathological. It is expected in cases of empyema or other extensive pus-for mations: (1) the ulcerative stage of typhoid fever, (2) suppUrative processes, (3) pneumonia at the crisis, (4) after childbirth, (5) in carcinomatous affec tions, and (6) in phosphorus poisoning. T. P. Prout (Phila. Med. Jour., Feb. 10, 1900).
The urine may, of course, also contain albumin in connection with hmmaturia and hmmoglobinuria, but such cases can not be classed as true albuminuria.
Physiological Albuminuria.—Regard ing the origin of the albumin in the urine only guesses can be made; two theories are possible: (1) the albumin may come from the glomeruli; (2) from the tubular epithelial cells.
Formerly the opinion predominated that the fluid which escaped from the glomeruli was albuminous, but that the albumin was absorbed during the passage through the healthy renal tubules, dis eased tubular epithelium being unable to absorb the albumin. This has not been proved, however, and most modern authors believe that albumin is not contained in the urine coming from the glomeruli, except when these are diseased or when the pressure of blood in the glomeruli is abnormally great. Runeberg, on the contrary, is of the opinion that albuminuria is caused by I low pressure of blood, and supports this opinion by experiments with animal membranes, but experiences with dead membranes cannot be regarded as con clusive for the action of the living kidney.