Large opaque hemithorax due to cardiomegaly and atelectasis.

We studied the clinical and radiologic features of five infants with a large opaque left hemithorax due to the combination of cardiomegaly and atelectasis. The causes of cardiomegaly were cardiomyopathy (two patients), congestive heart failure due to fluid overload, congenital mitral insufficiency, and idiopathic hypertrophic subaortic stenosis. In all five patients, there was initial total opacity of the left hemithorax with shift of the heart and mediastinum to the right due to the combination of cardiac enlargement and total lung collapse. The correct diagnosis may be suggested from conventional chest roentgenograms. Noninvasive supplementary studies, such as high-kilovolt roentgenography, fluoroscopy, esophagography, echocardiography, and radionuclide angiography, should be done for clarification.