Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Emphysema and Overinflation
Pulmonary emphysema consists of distention of air spaces with irreversible disruption of the alveolar septa. It can involve part or all of a lung. Overinflation is distention with or without alveolar rupture and is often reversible. Compensatory overinflation can be acute or chronic and occurs in normally functioning pulmonary tissue when, for any reason, a sizable portion of the lung is removed or becomes partially or completely airless, which can occur with pneumonia, atelectasis, empyema, and pneumothorax. Obstructive overinflation results from partial obstruction of a bronchus or bronchiole, when it becomes more difficult for air to leave the alveoli than to enter. Air gradually accumulates distal to the obstruction, the so-called bypass, ball-valve, or check-valve type of obstruction.
Localized Obstructive Overinflation
When a ball-valve type of obstruction partially occludes the main stem bronchus, the entire lung becomes overinflated; individual lobes are affected when the obstruction is in lobar bronchi. Segments or subsegments are affected when their individual bronchi are blocked. When most or all of a lobe is involved, the percussion note is hyperresonant over the area and the breath sounds are decreased in intensity. The distended lung can extend across the mediastinum into the opposite hemithorax. Under fluoroscopic scrutiny during exhalation, the overinflated area does not decrease and the heart and the mediastinum shift to the opposite side because the unobstructed lung empties normally.
Unilateral Hyperlucent Lung
The differential diagnosis for this resultant unilateral hyperlucent lung is quite broad and can involve the lung parenchyma, airways, pulmonary vasculature, chest wall (see Chapter 445 ), and mediastinum. Localized obstructions that can be responsible for overinflation include airway foreign bodies and the inflammatory reaction to them (see Chapter 414 ), abnormally thick mucus (cystic fibrosis, Chapter 432 ), endobronchial tuberculosis or tuberculosis of the tracheobronchial lymph nodes (see Chapter 242 ), and endobronchial or mediastinal tumors.
Patients with unilateral hyperlucent lung can present with clinical manifestations of pneumonia, but in some patients the condition is discovered only when a chest radiograph is obtained for an unrelated reason. A few patients have hemoptysis. Physical findings can include hyperresonance and a small lung with the mediastinum shifted toward the more abnormal lung.
Swyer-James or Macleod Syndrome
The condition is thought to result from an insult to the lower respiratory tract following most commonly adenovirus (see Chapter 289 ) or respiratory syncytial virus (see Chapter 287 ), Mycoplasma pneumoniae (see Chapter 250 ), or measles (see Chapter 273 ). The infection can cause pulmonary vascular hypoplasia with resultant hypoperfusion leading to unilateral hyperlucent lung (underdevelopment). Clinically, children with this condition often have chronic cough, recurrent pneumonia, hemoptysis, and wheezing, although some are asymptomatic. Some patients show a classic mediastinal shift away from the lesion with exhalation. CT scanning or bronchography can often demonstrate bronchiectasis. Thorascopic evaluation may be useful. The triad of unilateral hyperlucent lung, diffusely decreased ventilation, and matching decreased perfusion of the affected lung supports the diagnosis. In some patients, previous chest radiographs have been normal or have shown only an acute pneumonia, suggesting that a hyperlucent lung is an acquired lesion. For those with recurrent infection or severe lung destruction, treatment may include immunization with influenza and pneumococcal vaccines, as well as surgical resection. However, without treatment, some individuals may become less symptomatic with time.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here