|
DIAPHRAGMATIC HERNIA
Overview
The diaphragm is the muscular separation between the chest and abdominal cavities that functions as a barrier and aids in respiration. Diaphragmatic hernia is disruption of the diaphragm which allows abdominal organs to migrate into the chest cavity. Most dogs and cats that suffer diaphragmatic hernias have been hit by a car or have experienced some other type of trauma.
Predilection
Diaphragmatic hernia can occur in any dog or cat, but because they are caused by trauma, most dogs are young intact males, and most affected cats spend time outdoors.
Clinical Signs
Acutely, diaphragmatic hernia can cause significant respiratory difficulty. The trauma which caused the hernia may also result in rib fractures, lung lacerations, and lung bruising. These injuries may lead to pneumothorax (air in the chest outside of the lungs), or hemothorax (blood in the chest cavity). If abdominal contents have entered the chest cavity, this can further compromise the ability to expand the lungs. If the initial insult is tolerated, a diaphragmatic hernia may be diagnosed later in an asymptomatic animal. Chronically, abdominal organs, such as the liver or intestines can become adhered in the chest cavity and the animal may exhibit signs associated with liver or gastrointestinal disease such as vomiting or anorexia.
Physical Exam
Heart sounds may be muffled on the side of the hernia, or more intense on the other side. Shallow or rapid breathing may be noted. Evidence of trauma, such as abrasions, may be noted.
Diagnostics
Chest radiographs must be taken to diagnose the disease, and to look for any other abnormalities. In the normal animal, a diaphragmatic line, a cardiac silhouette, and air-filled lung fields are appreciated on chest radiographs (Figure 1). In the case of diaphragmatic hernia, loss of the diaphragmatic line, loss of the cardiac silhouette, displacement of lung fields, and presence of abdominal contents within the chest cavity may be noted on chest radiographs (Figure 2).
Figure 1. Normal feline thoracic radiograph.
Figure 2. Thoracic radiograph of a cat with a diaphragmatic hernia.
Most cases of diaphragmatic hernia can be diagnosed from radiographs. However, fluid in the chest cavity can obscure the diaphragmatic line in the absence of a hernia. In this case, ultrasound may be helpful to differentiate abdominal organs from pleural fluid. Contrast radiography, performed by injecting contrast material into the abdominal cavity, and computed tomography may also be helpful.
Treatment
Surgical treatment should be performed as soon as the patient is stable, but not before. Surgical hernia repair performed within 24 hours of injury has the highest mortality rate due to shock and surgical and anesthetic stresses. Animals should therefore be treated for shock and given supplemental oxygen during the first 24 hours. Surgery is performed on an emergency basis only if the stomach is herniated into the chest cavity and becomes distended with gas. This can prevent lung expansion. A needle can be used through the chest wall to decompress the stomach, and then surgery can be performed. Surgical repair of the diaphragmatic hernia is typically performed by entering the cranial abdomen along the ventral midline, retracting the abdominal organs back into the abdomen, and suturing the rent in the diaphragm. A chest tube is placed to remove air, blood, or fluid that may accumulate. Find an ACVS Veterinary Surgeon.
Aftercare
The chest tube that was placed prior or at the time of surgery will remain in place until no further air, blood, or fluid is recovered. During this time the animal will remain in the hospital and will receive oxygen, and pain medication. Once the chest tube has been removed, the animal can go home. Most animals will begin to feel better after surgery and will want to be active. It is important to encourage rest and avoid activity during the post-operative period.
Prognosis
The prognosis for animals presenting with a traumatic diaphragmatic hernia is variable depending on other injuries incurred. It is estimated that roughly 15% of animals suffering traumatic diaphragmatic hernia will die before presentation. Of the patients that survive to presentation, the timing of surgery will also affect prognosis. Animals that have surgery greater than 24 hours after trauma have a lower mortality rate than those having surgery within the first 24 hours owing to resolution of shock. Animals having surgery greater than 1 year after the initial insult carry a poorer prognosis due to the presence of adhesions.
—Brenda Salinardi, DVM, MS
Diplomate ACVS, Small Animal Surgery
Posted 9/23/2009
| 
