Fig. 224.—Schema of the position of the organs in the hernia represented by Fig. 223. D, Diaphragm; FF1, liver; Pl, pleura; Fe, omasum; Re, reticulum; CC, abomasum.
Lesions. The lesions vary greatly. In accidental diaphragmatic hernia they are confined to rupture of the diaphragm, sometimes of the liver, and to changes in the reticulum or omasum.
In intra-mediastinal hernia the layers of the mediastinum form a true hernial sac, and if the lesion is of old standing the displaced viscera may become attached to it, compressed, and partially strangulated.
Diagnosis. The diagnosis is very difficult, at all events in mediastinal hernia, and can only be arrived at by a process of exclusion. The most significant symptom is progressive stasis of food within the rumen, suggestive of some obstacle in the alimentary canal.
Prognosis. The prognosis is extremely grave, because it is impossible to reduce the hernia.
Treatment. No treatment is possible. The essential point is to confirm the diagnosis as soon as possible and to slaughter the animal while it is yet in good condition.
EVENTRATION.
Eventration belongs to the same group of lesions as herniæ, of which it is merely a more serious form. It differs from them only in the fact that the entire abdominal wall is injured. The skin, muscle, and peritoneum are torn, and the digestive organs pass into direct communication with the external air.
The name eventration has also been given to enormous subcutaneous abdominal herniæ, in which the sero-muscular wall is injured over a large area and the viscera become displaced and separate the subcutaneous tissue layers while at the same time they alter the whole shape of the abdomen.
Causation. The cause is always the same—some grave mechanical injury to the abdominal wall, producing an extensive perforation. The injury may be due to a horn thrust or to the animal falling on some sharp-edged body.