Neonatal opaque right lung: delayed fluid resorption.

Eight newborn infants with opaque right lungs were examined. Clinically, the main problem associated with the opaque right lung is mild respiratory distress, and radiographically, the findings consist of (a) a totally opaque right lung, (b) a semiopaque right lung or (c) an opaque right lobe only. These findings are usually interpreted as representing pneumonia, empyema, or hydrochylothorax, but the fact that they clear within 24 to 48 hours indicates that none of of these diseases is the cause. It is thought that neonatal opaque right lung results from the transient retention of normal fetal fluid in the right lung.