In cases of passive and secondary congestion, treatment must be directed towards improving the condition of the organ primarily affected, whether it be the heart, liver, or lymphatic glands.
ACUTE NEPHRITIS.
The term nephritis applies to inflammation of the renal tissues. Clinically, two forms only can be distinguished, the acute and the chronic.
As regards its pathological anatomy, the inflammation may principally affect either the interstitial tissue or the epithelial parenchyma, a fact which has suggested the division of the condition into epithelial nephritis, interstitial nephritis, and mixed nephritis. Clinically, such distinctions are impossible; and in reality all forms of nephritis are to a varying degree mixed, the lesions predominating in one or other of the constituent tissues. These lesions depend on the extent, intensity, and duration of the inflammatory attack, whatever the primary causes. All the constituent tissues of the kidney may be affected, simultaneously or individually: the Malpighian corpuscles, the convoluted tubules, the collecting tubules, or the interstitial connective tissue.
Causation. Cold seems to be an important factor. All acute or chronic intoxications in which the toxic principles are eliminated by the kidneys, such as poisoning by cantharides, fermented beet pulp, young shoots of trees or toxic plants, may cause acute nephritis.
Infectious diseases, such as gangrenous coryza, hæmoglobinuria, tuberculosis and post-partum infections, also play an important part, whether the nephritis be direct, that is to say, the result of the infecting agent itself, or indirect, i.e., produced by toxins generated in the body. In female animals gestation is an often unsuspected cause. Moussu believes that albuminuria is frequent during gestation, and although in most cases it is only of moderate degree, he thinks it is often associated with subacute nephritis, which might be aggravated by an accidental cause.
Many forms of nephritis are overlooked in consequence of their slight character.
Symptoms. The early symptoms are similar to those of congestion of the kidney, viz., dull colic, excessive sensitiveness over the region of the loins, passage of pink urine, loss of appetite, and fever. At a later stage, in cases of acute nephritis due to cold, the animal stands with the limbs close together and remains stationary, arching the loins and back, which are held stiffly. The animal obstinately refuses to move in consequence of the pain produced by so doing.
The general condition becomes grave, respiration is rapid, the pulse frequent, the artery tense, the muzzle dry, the accessible mucous membranes are injected, and appetite is almost entirely lost.
Urine is frequently passed, but the act causes pain, and the quantity is small. Absolute anuria is rare, and does not last long.