Dr. Pepe’s Diploma Casebook: CASE 120 – SOLVED!

Findings: PA view shows a triangular opacity at the right base (A, white arrow). A horizontal line (V sign) is visible at the right costophrenic angle (A, red arrow), and a lung-pleura interface above (A, blue arrow). The lateral view shows a sharp anterior lung-pleura interface (B, arrow). The appearance suggests partial RLL collapse and subpulmonary pneumothorax.

CT confirms the basal pneumothorax (A, arrow), with segmental collapse of the right lower lobe (B, arrow). In the axial view, the pneumothorax extends to the lung apex (C, arrow). There are bullae throughout both lungs.

Final diagnosis: subpulmonary pneumothorax secondary to ruptured bulla, causing segmental RLL collapse

This case illustrates the importance of radiographic signs (V sign in the case presented) to reach a correct diagnosis.

Radiographic signs can be defined as selected findings that help in the identification of specific processes. In my opinion, these signs can be very helpful to suggest the right diagnosis.

Signs should have two main characteristics: they should be recognizable, meaning that their appearance should be characteristic enough to be identified; and they should be useful, i.e. they should have a short differential diagnosis.

In the next Diploma Cases I will present valuable selected signs in the three main chest compartments: pleura/chest wall, lungs and heart/mediastinum.

Today I will focus on pleura/chest wall signs.

The first one is the V sign in pneumothorax.
The V sign is described as two intersecting lines forming a V, with the apex pointing laterally (Fig. 1). It represents a small amount of pleural bleeding secondary to separation of the two pleural layers in pneumothorax. Despite its name, the two lines of the V are rarely seen. Usually, only a single line is visible.
Importance of this sign: it helps to suspect pleural air when the pneumothorax is small or the presentation is atypical, as in the initial case.

Fig. 1. Typical V sign. Note the two branches of the V (A, white arrow), better seen in the cone-down view (B, red arrows), where the pneumothorax is more evident (white arrow). Note the drainage catheter (A, yellow arrow)

The V sign is not always present, but when visible, it is a useful indicator of a small or overlooked pneumothorax (Fig. 2). A confirmatory expiration film should then be performed (Fig. 3).

Fig. 2. PA radiograph shows a horizontal line at the right costophrenic angle (A and B, arrows). This line represents a small amount of pleural fluid and is very suggestive of an accompanying pneumothorax. Exploring the upper lung, a small pneumothorax is found in the apical region (A and C, arrows).

Fig. 3. 43-year-old woman with chest pain. A single V sign is visible at the costophrenic angle (A, white arrow). A partially hidden line of pneumothorax is seen in the right apex (A, red arrow). The expiration film better demonstrates the lung-pleura interface (B, arrows).

QUIZ: 58-year-old man after needle biopsy of a nodule in the right lung.

Do you see a pneumothorax?

Go to the next image for the answer.

Findings: PA radiograph shows a right basal pleural-lung interface (A and B, white arrows). Pleural air has collected in the right costophrenic angle, which is seen to extend much lower than on the opposite side in what is called the deep sulcus sign (A and B, red arrows). The carcinoma is located in the lower aspect of the right hilum (A and B, yellow arrows).

The deep sulcus sign is visible as a lucency of the lateral costophrenic angle, which is lower than usual. It is caused by pleural air collecting in the costophrenic angle. It is often better seen in supine radiographs (Fig. 4) and it is a useful clue for the diagnosis of pneumothorax in critically ill patients.

Importance of this sign: In a supine patient, it should raise the possibility of a pneumothorax. It is important in the intensive care setting after procedures such as insertion of a subclavian central venous catheter or before using positive pressure ventilation.

Fig. 4. Portable chest film showing a deep sulcus sign (A, red arrow) after several attempts to place a subclavian line. Two days later, after chest tube placement, the pneumothorax has resolved and the right costophrenic sinus has returned to normal (B, red arrow).

QUIZ: 65-year-old man with chest pain. Is the RLL nodule intra or extrapulmonary?

Go to the next image for the answer.

Findings: the RLL nodule has a sharp inner border (A, white arrow) and an indistinct outer border (A, asterisk). This combination of findings is called the incomplete border sign and indicates an extrapulmonary lesion. In addition, there is blunting of the right costophrenic sinus (A, red arrow), pointing to a probable pleural etiology. A previous film taken two years earlier (B) shows no changes. Axial CT confirms a pleural lesion with amorphous calcification (C, arrow). Surgical diagnosis: inflammatory pseudotumor of pleura.

The incomplete border sign occurs when an intrapulmonary mass is oblique to the X-ray beam. In these cases the mass is projected onto the lung, which outlines only the inner border. The lateral outline of the lesion disappears because is in contact with the chest wall which has the same radiographic density (Fig. 5).

Most common causes are: extrapleural fat, fibrous tumors of pleura, and rib lesions, among others.

Importance of this sign: It discovers extrapulmonary lesions and indicates a CT study to determine their radiological density.

54-year-old woman with pain in the right hemithorax.

Fig. 5. PA radiograph shows an apparent intrapulmonary lesion that is only well-defined in the inner aspect (A, arrow). The same occurs in the lateral view (B, arrow). CT clearly explains the incomplete border sign: the inner border is visible because it is outlined by air (C, white arrow), whereas the outer border is lost because it is in contact with the chest wall (C, red arrow). The underlying rib is eroded. Diagnosis: metastasis to anterior 4th rib.

It is important to emphasize that the etiology of extrapulmonary lesions cannot be determined on chest radiography unless we see rib destruction, in which case we suspect primary rib disease. If the underlying rib is normal, CT is needed to determine the density of the lesion: extrapleural fat, fluid, or soft tissue tumor (Figs. 6 and 7).

Fig. 6. 42-year-old man with pneumonia and pleural effusion. PA radiograph shows an extrapulmonary lesion with an incomplete border sign (A, arrow), most likely loculated pleural fluid. Enhanced coronal CT confirms the fluid and shows the draining tube in the loculation (B, arrow).

Fig. 7. 45-year-old man with mild cough. PA radiograph shows an extrapulmonary mass with an incomplete border sign (A, arrow). Unenhanced CT depicts an extrapulmonary soft tissue mass (B, arrow). Fibrous pleural tumor is the most likely diagnosis, confirmed at surgery.

Follow Dr. Pepe’s advice:

1. The V sign helps to suspect a small or atypical pneumothorax.

2. The deep sulcus sign is useful to suspect pneumothorax in supine patients.

3. The incomplete border sign places apparent pulmonary lesions in the extrapulmonary compartment.