This 2-month-old boy presented with acute severe tachypnea and a low-grade fever. The initial chest radiograph demonstrated normal pulmonary vascularity and lung volume (inflation) in the right lung. The left lung showed normal volume but was oligemic and appeared hyperlucent. The heart size was normal.
A table indicates the differential diagnoses of a hyper-lucent lung on chest radiographs in infants. In this case, radionuclide imaging studies included perfusion (Tc-99m MAA) and ventilation (Tc-99m DTPA) lung scans.
The studies confirmed a vascular etiology was responsible for the hyperlucent left lung. Echocardiography subsequently identified vegetations on the tricuspid valve as the source of the pulmonary emboli. These findings were surgically documented and the child completely recovered following the operation.