Radiologically, the differential diagnosis can include pneumomediastinum, congenital lobar emphysema, atelectasis with compensatory hyperinflation, congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, and a large pulmonary cyst. Clinically, it can present as any process that causes respiratory distress, and it is important to exclude other causes of respiratory distress in a neonate: RDS, endotracheal tube obstruction/displacement, aspiration, congenital heart disease, asphyxia, congenital diaphragmatic hernia (CDH), congenital cystic adenomatoid malformation (CCAM), or pleural effusions. Sudden rapid deterioration in a neonate can be from a tension pneumothorax, pneumopericardium, or a massive pericardial effusion/cardiac tamponade (umbilical venous catheter).
Pneumothorax
Symptomatic pneumothorax (includes tension vs nontension pneumothorax). Nontension symptoms: irritability, grunting, pallor cyanosis, restlessness, apnea, mild tachypnea, respiratory distress. Tension symptoms are noted in Section II.A previously.
Asymptomatic pneumothorax.
Persistent pneumothorax.
Pneumomediastinum. Air in the mediastinal space that may be confused with a true pneumothorax. On the radiograph, mediastinal air can elevate the lobes of the thymus (called “angel wing” or “spinnaker sail” sign), and the air can also track within the extrapleural space and outline the inferior aspect of the heart (“continuous diaphragm sign”). See Figure 11–19.
Congenital lobar emphysema. A rare anomaly of lung development that presents with respiratory distress and pulmonary lobar hyperinflation. Overdistention of one lobe secondary to air trapping occurs most commonly (47–50%) in the left upper lobe. Other lobe involvement is right upper lobe (20%), right middle lobe (28%), and lower lobes (rare). The causes of congenital lobar emphysema are multifactorial.
Atelectasis with compensatory hyperinflation. Compensatory hyperinflation may appear as a pneumothorax on a chest radiograph.
Pneumopericardium. In neonates, pneumopericardium and tension pneumothorax can both present as sudden and rapid clinical deterioration. In pneumopericardium, the blood pressure drops, heart sounds are distant or absent, and pulses are muffled or absent. Massive abdominal distention can also be seen. In tension pneumothorax, the blood pressure may initially increase, but then hypotension follows. The chest radiograph easily differentiates the two. A pneumopericardium has a halo of air around the heart (see Figure 11–18). The more common event is a tension pneumothorax. If one is unsure and time does not permit radiographic verification, quick transillumination can be done. If not available or unsure of results, it is better to insert a needle in the chest on the suspected side. If no response, then a needle should be inserted on the other side. If there is still no response, then the diagnosis of pneumopericardium should be considered.
Congenital diaphragmatic hernia (CDH). A developmental defect in the diaphragm allows the abdominal viscera to protrude into the chest, which causes pulmonary hypoplasia and decreased pulmonary vasculature and dysfunction of the surfactant system. Ninety percent are on the left side. CDH is often mistaken as a left tension pneumothorax. Presents with respiratory distress, cyanosis, and circulatory insufficiency. It can be hard to differentiate a left-sided pneumothorax from a typically left-sided CDH. With CDH, the abdomen is scaphoid, and the spleen cannot be palpated. There can be a mediastinal shift on radiograph. If chest tubes are placed, there is a risk of perforating the herniated viscus.
Congenital cystic adenomatoid malformation (CCAM). This rare congenital abnormality of the lung results from abnormal embryogenesis and reduced alveolar growth. The infants present with respiratory distress. Tachypnea and cyanosis can be presenting signs that are similar to a pneumothorax. Many of these are detected on ultrasound prenatally. A chest radiograph usually identifies the mass containing air-filled cysts. (See Chapter 135.)
Congenital pulmonary cysts. These are space occupying, involve one or more lobes, have atelectasis of the adjacent lobe, and have symptoms similar to pneumothorax.