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.

Prevalence of Radiographic Small Lung Opacities and Pleural Abnormalities in a Representative Adult Population Sample

“…The pleural fat and muscles inserting in the ribs sometimes create shadows difficult to distinguish from pleural thickening. Thus, the recording of slight lateral thickening, seen only "in profile" without other evidence of pleural thickening, can cause false-positive findings .l5, [20][21][22] Although thickening of the visceral pleura has been shown to occur not only as "diffuse" thickening, but also as local plaques, the circumscribed pleural thickening seen in radiographs mostly represents plaques of the parietal pleura. 15 · 2 3…”

The Ribs: Anatomic and Radiologic Considerations

“…Although these opacities are common, they have received little attention. Only Gilmartin (16) muscle that are visibly superimposed on the lung on frontal radiographs and are seen crossing the anterior ends of the ribs obliquely. However, two radiographic findings are inconsistent with Gilmartin's hypothesis.…”

Radiological pleural changes in nonpneumoconiotic silica-exposed coal miners

“…An idiopathic apical cap has been identified in 6% of people under 45 years of age and consists of nonspecific fibrosis of apical lung parenchyma that merges with the visceral pleura (19). Normal companion shadows in the chest wall, such as the serratus anterior muscle (20) and subpleural fat pads (21), may generate confusion by resembling localized, especially in the lateral chest wall, or generalized pleural thickening. Thus some of the pleural alterations found in our study may not have been significant.…”