Abnormal development of the diaphragm occurs for unknown reasons during gestation and prior to birth. Typically the hernia is between the abdominal cavity and the sac that contains the heart (pericardium). Abdominal organs can enter the pericardium and cause fluid accumulation within it and around the heart. The herniated organs and the fluid around the heart can impair function of the heart and lungs; however, many animals have this condition without any symptoms at all. In these animals the hernia may be found unexpectedly when X-rays of the chest are taken for some other reason. Vomiting
Animals with symptoms may have the following clinical signs:
Poor appetite or not eating at all
Abdominal distension from fluid accumulation
Shock or collapse
Animals that have been hit by a car, kicked, or have fallen from a height can get a tear in the diaphragm caused by an increase in pressure in the abdomen. They can also get a tear from a direct injury caused by a gunshot wound or a stabbing injury. Symptoms that an animal with a traumatic hernia might have are similar to those mentioned above for a congenital hernia, but in addition they are more likely to be in shock. They may also have other evidence of trauma, such as bleeding into the lungs or chest cavity, bruising of the lungs (pulmonary contusions) and fractures). As with congenital hernias, some animals seem normal and the diaphragmatic hernia is an unexpected finding.