Acute, Transient Middle Lobe Disease

1. Four cases of acute transient middle lobe disease have been presented.

2. The name middle lobe syndrome is suggested as an all inclusive term for all cases of middle lobe atelectasis regardless of etiology, and the name middle lobe disease for all those cases of atelectasis and pneumonitis which are not caused by active tuberculosis or by neoplasm.

3. Attention is being called to the fact that a considerable number of cases of middle lobe atelectasis may be of an acute and reversible nature. Due to the peculiar positioning of the middle lobe bronchus, drainage from an infected middle lobe is poor and mucus plug formation is frequent. As soon as the plug is expectorated or as soon as free drainage is reestablished, the lobe reexpands and a more favorable condition for the clearing of the pneumonitis is created. It is possible that chronic pneumonitis with or without atelectasis of the middle lobe (the latter may be obscured by the enlarged volume of the consolidated lobe) occurs as a result of failure of reestablishing free drainage. Bronchoscopy may be a therapeutic measure in some of these cases, in addition to being a diagnostic procedure.

4. Emphasis is placed on the importance of fluoroscopy in the lordotic position, since posteroanterior viewing may fail to demonstrate the shrunken middle lobe. A lateral film is of importance to establish the definite site of pneumonitis and atelectasis.