Peripheral middle lobe syndrome.

Classically, the middle lobe syndrome has been described as being caused by a central obstruction. Clinical records and radiologic findings were reviewed in 129 patients examined between 1955-1981 who had chronic disease in the right middle lobe and/or lingula. Fifty-eight patients (45%) had no evidence of a central obstructive lesion. The majority were middle-aged women with histories of chronic cough and chest pain. Bronchoscopic and radiologic evaluation served to exclude central lesions. Surgical confirmation was available in 38 patients. Pathologic study showed varying degrees of chronic inflammation, pneumonia, and bronchiectasis. Surgical results were excellent in isolated disease. Chronic atelectasis and pneumonitis of the right middle lobe and/or lingula do not always imply central obstruction. A lack of collateral ventilation is a plausible theory to explain the pathophysiology in such patients.