General Symptomatology

3.1 Projection Radiography

3.1.1 Generic Signs

The Fleischner Society has incorporated a number of generally accepted radiologic signs into its Glossary of Terms for Thoracic Imaging (see Chapter 25). Examples of these signs include the following:

Air bronchogram.
Air crescent sign.
Silhouette sign.

Knowledge of other general signs not featured in the glossary can at times be useful in radiologic differential diagnosis, e.g.¹:

Cervicothoracic sign: An intrathoracic mass whose cranial border is seen to project on posteroanterior (PA) radiographs superior to the clavicles must be located dorsally since the posterior portions of the lung apices extend farther cranially than their anterior counterparts.
Extrapleural sign: A mass arising from the chest wall, pleura or mediastinum which on a radiograph exhibits a blurred, ill-defined border with tapered margins and an obtuse angle, whereas an intrapulmonary lesion has a more defined border and acute angle. For more information, please consult Section 11.5 and ▶Fig. 11.9.
Gloved finger sign: Dilated, mucoid-impacted bronchi that on radiographs manifest as gloved fingers. This sign is typically observed in allergic bronchopulmonary aspergillosis and mucoviscidosis. But it can also present concomitantly with myriad other diseases secondary to longstanding central bronchial obstruction.

Golden S sign: This refers to the lateral bulging of a central tumor secondary to lobe atelectasis; see ▶Fig. 9.15. The resultant reverse S shape was initially used by R. Golden only to describe the external contour of the atelectatic area of the right upper lobe,² but this can also be applied to other lobes.

Table 3.1 Causes of unilateral changes in thoracic radiolucency on radiograph

Maximum decrease in unilateral radiolucency: “white-out hemithorax”	Large pleural effusion (see ▶Fig. 3.1)	Volume increase
	Total atelectasis (see ▶Fig. 3.2)	Volume reduction
	Pneumonectomy	Volume reduction, possibly surgical clips in mediastinum and hilum
Unilateral decrease in radiolucency	Pleural effusion (in particular, posterior on supine images)	Ultrasound
	Pneumonia	Inflammatory biomarkers
	Lung carcinoma	Volume increase
	Pleural carcinosis	Volume increase
	Pleural mesothelioma	Volume reduction
	Thoracoplasty	Calcifications, thoracic deformity
Unilateral increase in radiolucency	Congenital lobar emphysema	Massive hyperventilation of the deceased lung lobe
	Swyer-James syndrome	Vascular rarefaction
	Foreign body	Air trapping due to valve mechanism
	Central lung carcinoma	Rarely, air trapping due to valve mechanism, more commonly atelectasis

Deep sulcus sign: This refers to the abnormal increase in radiolucency seen on supine radiographs, originating from a costophrenic angle (sulcus) and extending into the lateral portions of the adjacent upper abdominal quadrant. This sign is indicative of anterior pneumothorax.

3.1.2 Unilateral Changes in Radiolucency

There are several causes for increased or decreased radiolucent hemithorax. Important causes as well as tips on differential diagnosis are presented in ▶Table 3.1; two examples are illustrated in ▶Fig. 3.1 and ▶Fig. 3.2.

3.1.3 Atelectasis

The term atelectasis is used to denote hypoventilation of the lung parenchyma, often caused by bronchial obstruction. This and other causes are listed in ▶Table 3.2.

Fig. 3.1 Large right-sided pleural effusion. Radiograph. Mediastinal displacement to the left. Total compression atelectasis of the right lung.

Table 3.2 Causes of atelectasis

Causes	Examples
Bronchial obstruction	Central tumor
	Inflammation (mucoid impaction)
	Foreign body
	Lymphadenopathy
Relaxation atelectasis	Pneumothorax (atelectasis secondary to intrinsic lung elasticity)
Compression atelectasis	Pleural effusion
	Large tumors of mediastinum, pleura and chest wall
	Diaphragmatic hernias
Surfactant deficiency	Adult respiratory distress syndrome

Atelectasis of an entire lung gives rise to the image of a “white-out hemithorax” (for differential diagnosis, see above). Atelectasis of individual lung lobes has a characteristic appearance specific to the implicated lobe:

Right upper lobe atelectasis (▶Fig. 3.3): The right upper lobe collapses in a cranial and mediastinal direction. This, in turn, causes cranial displacement of the minor (horizontal) fissure, in particular, of the lateral portion. It also results in a high-riding diaphragm on the right. If atelectasis is caused by a central tumor, the tumor can at times be identified as bulging of the external contour of the atelectatic area, known as the Golden S sign.
Middle lobe atelectasis (▶Fig. 3.4): The middle lobe collapses in an inferoposterior direction. On PA radiographs, this is seen as an upward directed, smoothly marginated opacity, whereas on lateral views it manifests as anterobasal triangular opacity.

Fig. 3.2 Total atelectasis of the left lung secondary to central lung carcinoma. Radiograph. Lung metastasis in right upper lobe (arrow).

Fig. 3.3 Right upper lobe atelectasis. Radiograph. Atelectasis can be clearly identified on the PA radiograph (arrows).
Right lower lobe atelectasis (▶Fig. 3.5): The right lower lobe collapses in a medioinferior direction. On PA radiographs, it causes right paracardiac and smoothly marginated lateral opacity. If this is misinterpreted as the right heart border, right-sided lower lobe atelectasis can be overlooked.