ALBUMINURIA - URINE.
Since the time of Richard Bright the presence of albumin in the urine has been regarded as a proof of kidney disease both by physi cians and by the laity. And in spite of all evidence to the contrary this is still the popular belief. It is true that any educated phySi cian will now admit that albumin may be absent with kidney disease and present without it, but this admission is largely theoretical. In practice the old belief makes itself felt, and the presence of albumin is still looked for as the main evidence of disease of the kidneys.
The general belief concerning the albumin has been that it is re moved from the blood by the kidneys just as urea or sugar is, and that if large quantities of it are removed from the blood the compo sition of this fluid is changed. A good deal of pains has been taken to discover why it is that diseased kidneys should excrete albumin.
As a matter of fact the presence of serum albumin and serum globulin in the urine means that the blood serum, of which they are constituents, has become mixed with the urine. The simplest way
in which this can happen is to have bleeding from the bladder or kidneys so that the blood and urine are mixed. The ordinary way is for the blood serum to transude from the kidney capillaries just as it does from capillaries in other parts of the body. Albumin in the urine, therefore, means the same thing as serum in a serous cavity, that there has been a transudation of serum from the vessels. To keep the matter clear in our minds, whenever we use the word albu minuria we should do so with the idea that it is a popular way of say ing that the urine has blood serum mixed with it. In this way we will think of the kidney as we do of other parts of the body—as lia ble to exudations of serum either of inflammatory or of dropsical char acter. But, just as in the serous membranes the exudation is not in the membrane but in its cavity, so in the kidney the exudation is not into the parenchyma but into the tubules.