A full-term infant developed respiratory distress six hours after uncomplicated vaginal delivery. The chest x-ray (shown) indicates that the diagnosis is

A. congenital diaphragmatic hernia-Bochdalek type.
B. congenital diaphragmatic hernia-Morgagni type.
C. congenital lobar emphysema.
D. cystic adenomatoid malformation.
E. staphylococcal pneumonia with pneumatocele formation. 

Answer A

Congenital diaphragmatic hernia of the Bochdalek type occurs in approximately 1 in 4000 live births and is characterized by a posterolateral defect in the muscular portion of the diaphragm. Eighty-five percent of Bochdalek hernias occur on the left where the abdominal contents are found lying freely in the chest cavity. There is associated pulmonary hypoplasia and mediastinal shift away from the hernia. Three out of four patients present with respiratory difficulty within the first few hours of life. The diagnosis is made radiographically by the findings of abdominal contents in the chest with mediastinal shift to the contralateral side. 

A Morgagni-type congenital diaphragmatic hernia is usually a small anterior defect at the lower border of the sternum and is due to a musculo-fascial defect where the diaphragm meets the xiphoid. Often asymptomatic, these hernias may present with incarceration or strangulation of contained bowel. 

Congenital lobar emphysema involves hyperinflation of one lobe (most frequently the left upper) with resultant compression of the uninvolved lung. Radiographically, the involved side is hyperlucent and there is mediastinal shift away from the hyperinflated lobe. Presentation is within the first week of life in 50% of cases and treatment involves removal of the involved lobe. The etiology may be abnormally weakened cartilage development with resultant expiratory airway collapse and air-trapping. 

In cystic adenomatoid malformation the normal pulmonary parenchyma is replaced with multiple cysts. Radiographically, the multicystic "Swiss cheese" pattern may resemble that seen with a Bochdalek hernia, but the patient with a cystic adenomatoid malformation has a normal abdominal bowel gas pattern. Cystic adenomatoid malformation frequently presents in the newborn but half of patients present as older infants and children in which case the radiograph is often of chronic consolidation. The treatment of cystic adenomatoid malformation is resection of the involved area--generally lobectomy. 

Staphylococcal pneumonia may be complicated by pneumatocele formation. Radiographically, this appears as clusters of small air spaces in areas of previous consolidation. The condition is not generally seen in newborns and is characterized by gradual resolution over several weeks to months.