contents into the chest cavity.
hiatus hernia
The hiatus hernia is more often acquired than congenital but is occasionally seen congenitally. Bochdalek hernia is by far the most common. A ventral diaphragmatic hernia is often associated with a pericardial defect, a lower sternal defect and upper abdominal wall deficiency, and is known as Cantrell's pentalogy. Not all cases are complete.
The outcome for infants following repair of a Bochdalek-type hernia depends on the degree of associated pulmonary hypoplasia; the lung is compressed by the presence of viscera in the thoracic cavity which interferes with its normal lung development. In addition, the mass effect of the viscera can lead to shift of the heart and the mediastinum to the contralateral side, resulting in further compression. Malrotation is a common association of diaphragmatic hernia. The diagnosis of diaphragmatic hernia is made antenatally by the finding of bowel loops in the thoracic cavity. Clinically, children present with grunting aspiration, often a scaphoid abdomen as the bowel loops are in the chest, and respiratory difficulty in severe cases.
Imaging
Radiologically, the appearances are typical. Once air is present in the bowel, multiple loops of air-filled bowel can be identified in the chest (Fig.1). A nasogastric tube will be also in the chest if the stomach is herniated. There is shift of the heart and mediastinum away from the side of the hernia, usually to the right as the defect is mainly on the left. On the right, hernias are more frequently of the Morgagni variety than Bochdalek. Because of the presence of the liver, which temporarily occludes the defect, there may be delayed presentation, which can lead to diagnostic difficulty. The history is frequently that of a child who has had a respiratory tract infection who goes on to develop an opaque chest.
Radiologically, the diagnosis can usually be made from the plain film. Ultrasound is particularly useful on the right in identifying the extent of the intact diaphragm and position of the liver. In cases of doubt, MR imaging is helpful. Imaging in the coronal plane can also demonstrate the herniation.
Any hernia may be detected as an incidental finding on a routine chest radiograph but this is more likely to happen with a Morgagni or a hiatal hernia than a Bochdalek hernia.
Delayed presentation
Delayed presentation also may occur with Bochdalek hernias and can lead to considerable diagnostic confusion (Fig.2). In these circumstances the defect in the diaphragm is usually small. There is herniation of bowel through the defect but the bowel may undergo volvulus and necrosis. The child then presents with a faeculent pleural effusion. Radiologically, these children usually present with a large pleural effusion and rapid onset of respiratory symptoms. The stomach bubble is usually correctly located within the abdomen and there is often no air present in the twisted bowel in the chest. This leads to further diagnostic confusion. The diagnosis in suspected cases is best achieved by a combination of ultrasound and cross-sectional imaging which will show the bowel loops in the chest. The diagnosis may also be suspected on contrast studies as the abnormal orientation of a loop of bowel will be identified, but it is quicker to make the diagnosis by ultrasound or cross-sectional imaging.
Prognosis
Children who survive the surgery for the repair of a congenital diaphragmatic hernia in the neonatal period usually have some degree of pulmonary hypoplasia, although this varies from being minimal to severe. The functional assessment of the lungs is best shown by VQ lung scanning. Impairment of ventilation is usually greater than impairment of perfusion. See Morgagni hernia, Bochdalek hernia.