Synonym.—Lardaceous or Waxy Degeneration of the Kidney.
Definition.—A degeneration in which a peculiar proteid substance, lardacein, is deposited in the walls of the capillaries and connective tissue-cells of the kidney.
Etiology.—This form of kidney is always associated with amyloid degeneration of some other part, such as spleen, liver, etc., and, although it is frequently associated with Bright's disease, should not be regarded as a variety of chronic nephritis, as it may occur independently of it. While the cause is obscure, it is most likely due in some measure to retrograde changes in the blood plasma, whereby the blood is unable to manufacture normal tissue. It is secondary to chronic suppurative diseases, especially those of the bones, and is often tubercular. Ulceration of the bowels, tuberculosis, anal fistula, the ulcerative stage of syphilitic deposits in the bone, and, in fact, any chronic suppurative process whereby there has been a long-continued drain on the albumin—gout, cancer, malaria, leukemia, and chronic valvular diseases—have been associated with the amyloid kidney; but just how much, if any, these diseases are responsible for the degeneration is not known.
Pathology.—The kidney presents a characteristic appearance. It is large, smooth, and of a grayish-white or yellow color. On section the cortex presents a peculiar glistening appearance or resembles bacon. It is tough and increased in width. The malpighian bodies stand out prominently, and may sometimes be distinguished with the naked eye. The pyramids are of a dark-red or mottled appearance. On applying Lugal's iodin solution, the degenerated tissue turns a brownish-red or a dark-mahogany or nut-brown color, which, on the addition of dilute sulphuric acid, usually changes to blue.
Microscopically the changes as given by Strumpell arc as follows: "We find first the amyloid degeneration, which, in varying extent and combination, affects most frequently the glomeruli and also the capillaries of the cortex, the vasa recta, and sometimes the membranae propriae of the uriniferous tubules. In pure amyloid kidney the rest of the renal tissue is normal, but in many cases we find changes in the epithelium,—fatty degeneration, desquamation, and disintegration, and also, not infrequently, interstitial cellular infiltration."
Symptoms.—The symptoms many times are quite obscure, and only discoverable post-mortem. Preceded as it is by some chronic suppurative or wasting disease, the symptoms are masked or overlooked. The urine varies as to quantity, and may be slightly diminished, normal, or increased, usually the latter. Frequently the patient is required to arise several times during the night to void water, the total amount reaching one hundred ounces. It is generally very pale or straw-colored, of low specific gravity, 1,005 to 1,015, has but little sediment, and varies as to the quantity of albumin present. There may be only traces present, though it is usually quite free, and in rare cases there is none present. Where casts are present, they are of the hyaline, fatty, or granular type.
Dropsy is not a marked feature, though usually present in the ankles and legs, sometimes becoming general. Dyspeptic symptoms are quite common, with furred tongue, unpleasant breath, and occasional vomiting. The liver and spleen are generally enlarged, the sharp outlines of these organs being of diagnostic value.
Diarrhea is quite common, especially late in the disease, and is often due to degeneration of the same character taking place in the intestines or tubercular ulcers. A waxy complexion is common. There is usually no cardiac disturbance.
Diagnosis.—The history of some chronic affection, such as suppurative bone disease, syphilis, tuberculosis, chronic malaria, fistula, and other wasting diseases associated with enlargement of the liver and spleen, and the passing of a large quantity of pale, albuminous urine of low specific gravity, and hyaline or granular casts, make the diagnosis almost sure.
Prognosis.—This is usually grave. The disease comes on so insidiously that degeneration is well established when recognized.
Treatment.—This will consist in an effort to raise the quality of the blood-supply. With a blood rich in red blood-corpuscles, degeneration is at an end. Hence our attention will be turned to correcting the associated ulceration or suppurative lesion.
The bitter tonics, the chlorates, sulphites, mineral acids, echinacea, etc., will be found useful. A nutritious but easily digested diet, exercise in the open air, the avoidance of colds, and a line of treatment suitable to chronic Bright's disease will give the best results.