4. The kidneys have been compared to mucous membranes, and authors speak of catarrhal and croupous nephritis.
5. The disease has been classified, according to the particular part of the kidney affected, into parenchymatous, tubular, glomerular, interstitial, and diffuse nephritis.
With our present knowledge of the subject it seems to me most convenient to speak of acute and chronic parenchymatous nephritis and acute and chronic diffuse nephritis. I include under the head of parenchymatous nephritis all those kidneys in which the lesions are strictly confined to the epithelial cells lining the tubules and the capsules of the glomeruli; under the head of diffuse nephritis, those kidneys in which the lesions involve the tubes, stroma, glomeruli, and arteries; under the head of interstitial nephritis, those kidneys in which the essential morbid changes are in the stroma.
This classification seems to me to be theoretically correct, but yet I must admit that from a clinical standpoint nearly all the cases may be conveniently arranged into the two classes of acute and chronic Bright's disease.
GENERAL SYMPTOMS OF BRIGHT'S DISEASE.—There are a certain number of symptoms common to all the varieties of Bright's disease, and it is convenient to consider them before going on to the special description of each of these varieties. These symptoms are—
Changes in the Urine.—Healthy adults usually secrete during the twenty-four hours from 40 to 50 ounces of urine of a light-yellow color, of acid reaction, of a specific gravity of 1015 to 1025, and holding in solution a number of excrementitious substances. Small amounts of albumen and of sugar seem to be, in some persons, physiological ingredients of the urine.
In most cases of Bright's disease the quantity of the urine at some time in the course of the disease deviates from the normal standard. Either the urine is increased in amount or diminished or suppressed, and in the course of the same case the urine may be at one time increased, at another diminished.
We find in healthy persons that the quantity of urine varies with the amount of fluids that are imbibed and with the condition of the skin and the bowels—that nervous influences and certain drugs will increase or diminish the amount of urine. Physiologists teach us that the amount of urine excreted varies with the degree of the blood-pressure in the renal arteries or with the rapidity with which the blood circulates through these arteries.
The urine may be very much increased or diminished in amount as the result of various morbid conditions. Scanty urine or suppression of urine is observed in the course of acute parenchymatous and acute diffuse nephritis and in the early stages of the development of the large white kidney. During the course of any case of chronic Bright's disease there are usually periods during which the urine is scanty or suppressed, especially toward the close of the disease. The kidney lesions which complicate scarlet fever, yellow fever, and cholera are often attended with suppression of urine. Any diseases accompanied by a well-marked rise of temperature are apt to be associated with a diminution in the amount of urine. Injuries to the urethra, even very slight ones, may be followed by complete suppression of urine, without any changes in the kidneys except congestion.
Marked diminution in the amount of urine occurring in the course of acute and chronic Bright's disease is usually associated with the development of cerebral symptoms—headache, restlessness, delirium, muscular twitchings, convulsions, stupor, and coma. Such a change in the amount of the urine usually lasts only a few days and may terminate fatally, or the quantity of urine will increase and the patient get better. There are, however, cases in which the suppression of urine lasts for several days without the development of uræmic symptoms. Whitelaw1 relates a case of suppression of urine lasting for twenty-five days in a boy eight years old. The suppression began twelve weeks after an attack of scarlatina. There were no uræmic symptoms, and the child recovered completely.