The Serratus Anterior Muscle on Chest Radiographs

Abstract

The radiographic appearance of the serratus anterior muscle shadow is analyzed. In frontal and near-frontal views, it produces a bowling-pin silhouette. When the muscle is well-developed, the medial edge of this silhouette may be superimposed upon the air shadow of the lung in a variety of ways. When it overlies the apex of the lung, it gives rise to the companion shadow; when overlying the midlateral lung edge and costophrenic angle it may mimic pleural and/or extrapleural disease. Recognition of the various possible patterns is important to prevent overdiagnosis of disease, particularly asbestosis.