If there has been simple lack of circulation the kidney becomes flaccid, pale and small in size. The secretory elements (glomeruli and uriniferous tubes) are first absorbed, leaving the fibrous network, which tends to shrink and form a hard resistent mass. In extreme cases there may be absolutely no glandular tissue left, and the dense shrunken mass represents only the hyperplasia of the original fibrous network. In the different successive stages of this process the glomeruli and tubules become flattened, the epithelial cells become granular, or contain colloid casts and refrangent elements like oil globules and finally they are represented by a small mass of fibrous material.
Of all the atrophies caused by the pressure of tumors perhaps that caused by cysts is the most characteristic. There may be a single cyst or they may be multiple; they may range in size from a pea to the size of the two fists the total size exceeding that of the normal kidney. In all such cases the cysts project visibly from the surface of the organ. They vary according to their origin and nature. Congenital cysts are said to have resulted from distension by retained urine of the capsule of the glomerulus. The arterial tuft is atrophied and flattened against the wall. Serous cysts with clear contents are found in the old. Urinous cysts again form by distension of the tubules that are obstructed by cysts or minute calculi. Colloid cysts are found in certain forms of nephritis formed by the dilatation of the capsule of the glomerulus or of the uriniferous tubules. The liquid often contains leucin, tyrosin and cholesterine. In all such cases the walls of the cyst become thick, and the glandular parenchyma is compressed leading to progressive degeneration and atrophy.
Symptoms of atrophy of the kidney are necessarily those of suppression of urine, with, in certain cases, the passage of casts of the uriniferous tubes and of crystals of salts. There are, however, no absolutely pathognomonic symptoms. When the kidney can be reached through the flaccid walls of a comparatively empty abdomen, or through the rectum, its hard, shrunken condition may assist in diagnosis.
Treatment is not successful in advanced cases. Prevention is to be sought by obviating or treating the conditions on which the atrophy depends. Nephritis must be treated on general principles. Calculi must be avoided by a liberal supply of water, by soiling, or by pasturage. Strongylus parasitism should be dealt with by destroying the parent worms in the bowels, and by securing pure drinking water free from their eggs and embryos. Cysts, and tumors are only amenable to surgical measures and not often open even to these.
FATTY DEGENERATION OF THE KIDNEY: STEATOSIS OF THE KIDNEY.
Causes: age, overfeeding, idleness, atony, retention of urine. Lesions: kidney enlarged, pale yellow, capsule loose, cut surface glistening unctuous, oil globules in scrapings, granules soluble in ether. Symptoms: in idle, overfed, obese, improved meat producing breeds, closely confined, starchy or saccharine food, fatty granules in urine, finally dropsies, anæmia, debility, sluggishness. Prognosis unfavorable in advanced stage. Treatment: butcher, restricted regimen, open air exercise, nitrogenous diet, crossing, diuretic food or drugs, oil of turpentine, balsam copiaba. Palliation only.
Fatty degeneration of the kidneys is by no means unknown in the domestic animals. It has been observed in dogs and cats (Rogers, Goubaux, Vulpain, Trasbot). In dogs it has been erroneously set down as a characteristic lesion of rabies. Like fatty degeneration of other organs, it is also met with in old and overfed individuals of meat producing breeds of animals, in which the tendency to early maturity and rapid and excessive fattening has been fostered from generation to generation. In man small, granular, fatty kidney is a common result of chronic parenchymatous nephritis, and often coincides with fatty liver. Chronic poisoning by arsenic or phosphorus is another cause, as it is of fatty degeneration in other organs.
Vulpain has attributed it to a lack of active exertion and of general tone, associated with excessive amylaceous feeding, sluggish, shallow breathing and tardy elimination. Goubaux and Trasbot attach great importance to the compulsory retention of urine in house dogs, cats and horses. The damming back of the urine in the convoluted tubes and glomeruli, temporarily arrests secretion, and the inactive and compressed cells tend at once to granular and fatty degeneration.
Lesions. The gland is sensibly increased in size, and pale, yellowish or straw yellow. The capsule is easily detached from the cortical substance, contrary to what is the case in chronic productive inflammation. The cortical substance is increased in thickness, and pale, the pallor being largely in ratio with the duration or extent of the fatty degeneration. The cut surface may be glistening and unctuous to the touch. It is softer than usual, rather friable, and if scraped, furnishes a serous or grayish pulp in which oil globules are prominent features, together with granular epithelium and free granules that dissolve readily in ether. Tubules are varicose and unequal at different parts. The medullary portion has undergone little change. It may be paler at certain points, with some shrinking of its substance and increase of firmness.
Symptoms. As a rule the disease occurs in pampered, overfed and obese animals, and in those of the improved breeds which have great power of digestion, assimilation and fattening. It is especially to be looked for after close confinement on full, stimulating, amylaceous diet. Symptoms are not usually recognized during life. There is, however, a lessening of the urinary secretion, and, as the disease advances, albuminuria. When examined microscopically this is found to contain characteristic elements, such as granular epithelial cells, the granules soluble in ether, oil globules, and at times crystals of cholesterine (Beale). A diagnosis based on the mere presence of oil globules may, however, be fallacious, as these may be present in animals that have just been heavily fed on oleaginous food, and again the oil used to smear the catheter may float in the urine and prove misleading. Under such circumstances vaseline or glycerine may be substituted on the catheter. Scriba induced fatty urine by injecting fat or oil emulsion into the blood, and Chabrie by ligating the large intestine. Trasbot says that cylindroid casts may be present. As in other grave kidney affections, dropsies supervene as the disease advances. These may show in the limbs, in the abdomen, or in other serous cavities. A steadily advancing anæmia with pallor of the mucosæ, listlessness, weakness, debility and sluggishness are to be noted.