Horse. This is not a frequent lesion in solipeds, yet the number of cicatrices of the spleen which are found post mortem in old horses would indicate a considerable number of slight and non-fatal cases. The most common cause appears to be external violence and especially kicks or blows with horns on the left hypochondriac region. Horses running at large in pastures, or in yards, or standing side by side in short stalls or tied with too long halters are the usual victims. Cadeac refers to cases reported by Tausch, Millot, Berndt, Humbert and Pont, and one case occurring in a three year old colt came under the notice of the author. The subject stood in a stall to the right of an irritable mare, and though the kick left no noticeable skin lesion the colt died in three hours with symptoms of internal hemorrhage. At the necropsy a laceration of the spleen of about five inches long was disclosed, and a large quantity of blood had accumulated in the peritoneum.
Brandis mentions a case consequent on a violent fall on the left hypochondrium.
In other cases pre-existing disease of the spleen or its blood-vessels have proved active factors. In the friable degenerated spleen of leucocythæmia multiple small lacerations have been found (Peuch, Laulanie); in engorgement of the spleen consequent on thrombosis of the splenic vein (Wiart); in chronic indigestion with habitually loaded stomach compressing the gastric and hepatic arteries and determining a reflux of blood through the cæliac axis into the spleen (Mongin).
Finally, though less frequently than in the ox, the engorgement of the spleen with blood in cases of anthrax may be a cause of rupture.
Lesions. The rupture may be on any part of the spleen and it may be complete or incomplete; in the latter event the capsule may have ruptured while the more elastic peritoneal covering has remained intact enclosing a coagulum of variable size bulging above the level of the spleen. When the peritoneal coat has given way, its laceration is usually smaller than that in the spleen and its proper envelope. Any degeneration of the spleen will affect the appearance of the lesion. In one case caused by external violence the adjacent portions of the spleen were reduced to a soft pulp. In such a case there is a slow but continuous flow of blood in a small stream which may, however, prove fatal (Humbert and Pont).
Again in cases caused by external violence there may be fractures of the ribs, ecchymosis, local swellings or even wounds of the skin, but all these may be absent. The blood effused into the peritoneum is usually clotted. If the effusion has taken place slowly it is more or less coagulated around the edges of the wound or even in its depth and in this way the hemorrhage may be arrested. When the peritoneum is still intact the pressure of the clot beneath it has served to arrest the flow. In such cases the clot may be in part liquefied and absorbed and in part organized into fibrous tissue, constituting the cicatrices of the spleen found in old horses.
Symptoms appear to have been varied. Colicy pains are generally noted. Tausch has observed vomiting, Millot vertigo, and Wiart coma and trembling. In the author’s case the animal was found down, unable to rise, almost unconscious, pulseless, with great pallor of the visible mucous membranes, dilated pupils, and cold extremities. A diagnosis was made of internal hemorrhage, but its actual seat was only revealed post mortem.
Treatment. The early mortality usually forbids treatment. When opportunity is furnished keep the animal absolutely still and quiet, apply snow, ice or other refrigerant to the left hypochondrium, give internally tincture of muriate of iron, matico, or other astringent, and relieve any severe suffering by anodynes (hyoscyamus, belladonna, opium). External wounds may be treated antiseptically.
Cattle. The causes of laceration and hemorrhage of the spleen are similar to those acting in the horse. Blows with the horns on the left side, crowding through a doorway or gateway, and direct blows of other kinds are charged with its pathogenesis. The friability which attends on leucocythæmia has been noted as a predisposing cause. Calves by reason of their small size and the relative bulk of the spleen are especially liable to rupture by kicks from animals or men.
Much more commonly than in solipeds, rupture of the spleen occurs as a complication of specific microbian diseases like anthrax and Southern cattle fever.