MORBID ANATOMY - ACUTE EXUADATIVE NEPHRITIS.
In a nephritis of this type we should expect that the inflammatory products, the serum, white and red blood-cells, and coagulable mat ter from the blood-plasma, would collect in the Malpighian bodies and tubes, or infiltrate the stroma between the tubes; and that of the inflammatory products in the tubes and Malpighian bodies, a part would be discharged with the urine and a part be found in the kidney after death. We should also expect that the quantity of inflamma tory products would be in proportion to the severity of the inflamma tion, and that an excessive number of pus-cells would belong to the especially severe forms of the disease. Still further, it is evident that with the milder examples of nephritis, with but little exudation, no inflammatory products might be found in the kidney after death, all having been discharged into the urine during life.
As a matter of fact, the kidneys do present just such changes. In the mild cases we find no decided lesions iu the kidney after death.
In the more severe cases the kidneys are increased in size, their surfaces are smooth, the cortical portion is thick and white, or white mottled with red, or the entire kidney is intensely congested. If the stroma is infiltrated with serum, the kidney is succulent and wet; if the number of pus-cells is very great, there will be little whitish foci in the cortex.
In such kidneys we find the evidence of exudative inflammation in the tubes, the stroma, and the glomeruli, all the changes being most marked in the cortical portion of the kidney.
The epithelium of the convoluted tubes is often simply flattened. As this same appearance is also found in the chronic congestion of heart disease, it seems probable that this change of the shape of the cells is merely due to the inflammatory congestion.
In other cases, not only is the epithelium flattened but there is also a real dilatation of the cortex-tubes. This dilatation involves groups of tubes, or all the cortex-tubes uniformly.
In other cases, the epithelium of the convoluted tubes is swollen, opaque, degenerated, and detached from the tubes.
The tubes, whether with flattened epithelium or dilated, may be empty. More frequently, however, they contain coagulated matter in the form of irregular masses and of hyaline cylinders. The irregu lar masses are found principally in the convoluted tubes; they seem to be formed by a coagulation of substances contained in the exuded blood-plasma, and are not to be confounded with the hyaline globules so often found in normal convoluted tubes. The cylinders are more numerous in the straight tubes, but are also found in the convoluted tubes. They also are evidently formed of matter coagulated from
the exuded blood-plasma, and are identical with the casts found in the urine.
The tubes may also contain red and white blood-cells.
In the cases in which there is an excessive emigration of white blood-cells, we find these cells in the tubes, in the stroma, or distend ing the capillary veins. This excessive emigration is not necessarily attended with exudation of the blood-serum, and so the urine of these patients may contain no albumin. The white blood-cells are not usually found equally diffused through the kidneys, but are collected in foci in the cortex. These foci may be very minute, or may attain a considerable size.
The glomeruli regularly are changed. The cavities of the cap sules may contain coagulated matter and white and red blood-cells, just as do the tubes. The capsular epithelium may be swollen, some times so much so as to resemble the tubular epithelium, and this change is most marked in the capsular epithelium near the entrance of the tubes.
The most noticeable change, however, is in the capillary tufts of the glomeruli. These capillaries are normally covered on their outer surface by flat, nucleated cells, so that the tuft is not made up of naked capillaries, but each separate capillary throughout its entire length is covered over with these cells. There are also flat cells which line the inner surfaces of the capillaries, although not uni formly, as is the case in capillaries in other parts of the body. Still, in spite of the presence of all these cells, the outlines of the walls of the capillaries are fairly distinct.
In exudative nephritis the swelling and growth of cells on and in the capillaries change the appearance of the glomeruli. They are larger, more opaque, the outlines of the main divisions of the tuft are visible, but those of the individual capillaries are lost.
It is difficult to tell how much these changes in the glomeruli in terfere with the passage of the blood through their capillaries.
In most cases of exudative nephritis the patients recover, and the glomeruli return to their natural condition.
In some examples of exudative nephritis we also find a thickening of the walls of the branches of the renal artery within the kidney. This thickening is principally due to a swelling of the muscle-cells in the walls of these vessels.
All these changes in the kidneys are of such a character that they are not likely to be followed by a chronic nephritis. On the con trary, after the patients have recovered, the kidneys return to their normal condition.