Diaphragmatic hernia: Passage of a loop of bowel through the diaphragm muscle. This type of hernia occurs as the bowel from the abdomen "herniates" upward through the diaphragm into the chest (thoracic) cavity.

Diaphragmatic hernias may be congenital or acquired. Congenital diaphragmatic hernias are present at birth. They occur because of abnormal development of the embryo. Acquired diaphragmatic hernias are usually caused by traumatic injury.

Congenital diaphragmatic hernias most often occur to the back and sides of the diaphragm (more often on the left side than the right). Herniation in the front of the diaphragm is rare.

Diaphragmatic hernias can lead to protrusion of bowels into the chest cavity. Abnormal development of bowels and other organs may be associated and collapse of portions of the lungs can occur.

Congenital diaphragmatic hernias generally require surgical correction as ultimate treatment. Acquired diaphragmatic hernias may require operation, depending on the size and symptoms.