Traumatic Diaphragmatic Hernia

The diaphragm is a muscular wall that separates the chest (thoracic cavity) from the abdomen and plays a key role in breathing. A diaphragmatic hernia occurs when the diaphragm tears or fails to form normally, allowing abdominal organs to move into the chest cavity. This condition is often associated with significant trauma (for example, being struck by a car), and affected animals may have multiple concurrent injuries requiring urgent care.

Two main forms are seen in dogs and cats:

• Traumatic diaphragmatic hernia — caused by a tear due to an external event.
• Congenital diaphragmatic hernia — present from birth; the most common subtype is peritoneal-pericardial diaphragmatic hernia (PPDH).

Diaphragmatic hernia can lead to serious breathing impairment. The trauma that causes the tear may also result in rib fractures, lung tears, or pulmonary contusions, which can be complicated by:

• pneumothorax (air in the chest outside the lungs), or
• hemothorax (blood within the chest cavity).

When abdominal organs enter the chest, lung expansion becomes more difficult, worsening respiratory distress. Herniated organs may also have impaired blood supply.

With acute herniation, signs most often reflect reduced ability to expand the lungs, including:

• labored breathing,
• rapid, shallow respirations,
• an abnormal posture with the head and neck extended.

If the initial episode is survived, the hernia may be discovered later. Over time, organs such as the liver or intestines can become adhered within the chest, and animals may show gastrointestinal or liver-related signs (e.g., vomiting or loss of appetite).

Diagnosis relies primarily on thoracic radiographs (chest x-rays) and assessment for additional injuries. In normal animals, x-rays show a recognizable diaphragmatic boundary, a clear cardiac silhouette, and air-filled lungs. With diaphragmatic hernia, radiographs may show:

• loss of the normal diaphragmatic outline,
• poor definition of the heart silhouette,
• displacement/compression of lung fields,
• and abdominal organs visible within the chest.

Additional imaging may be recommended, including:

• abdominal and thoracic ultrasound,
• contrast radiography of the gastrointestinal tract,
• computed tomography (CT).

Surgery is the only definitive repair. The operation is performed once the animal is stable enough for general anesthesia. Some animals with severe respiratory compromise cannot stabilize until the displaced organs are returned to the abdomen.

Emergency surgery is indicated if the stomach herniates into the chest and becomes gas-distended, as this can prevent lung expansion. In such cases, the stomach may be decompressed by passing a needle through the chest wall prior to surgery.

Surgical repair is typically approached through a midline abdominal incision. The organs are returned to the abdomen and the diaphragmatic defect is closed with sutures. A chest tube may be placed to remove air, blood, or fluid from the thorax after the repair. Referral to an ACVS board-certified veterinary surgeon is common due to the complexity of these cases.

If organ blood supply has been compromised, partial removal of affected tissues (e.g., liver, gallbladder, spleen, stomach, or small intestine) may be necessary. In long-standing hernias, adhesions can make surgery more difficult and increase the risk of bleeding.

Hospitalization is required after surgery. Tubes placed during treatment (for drainage or feeding support) may remain for several days. Many patients also need inpatient care for other injuries. Effective pain control is a major part of recovery and is best managed in the hospital.

Most animals improve after surgery and may attempt to be active; however, rest and activity restriction are important during healing.

Prognosis in traumatic diaphragmatic hernia varies based on concurrent injuries. It is estimated that about 15% of animals with traumatic diaphragmatic hernia die before reaching veterinary care. Survival is best when shock is stabilized prior to surgery. Animals undergoing repair more than one year after the initial injury may have a poorer outlook due to adhesions.

For congenital PPDH, surgical mortality is low, and prognosis for return to normal function is generally excellent.