Dr. Pepe’s Diploma Casebook: CASE 122 – SOLVED!

Findings: PA radiograph (A) shows an apparently enlarged heart. Lateral view shows an anterior band limited by the mediastinal and epicardial fat (B, arrows). This finding, known as the pericardial band sign, is highly suspicious of pericardial effusion.

Cone-down lateral view shows the pericardial band better (C, arrows). In the radiograph three months earlier, the band was present, although thinner (D, arrows). Sagittal CT confirms the pericardial effusion (E, arrows).

Diagnosis: large uremic pericardial effusion simulating cardiomegaly

This week I will conclude the series of signs in chest imaging, presenting signs in the mediastinum. The first is the pericardial band sign.
The normal pericardium is 1-2 mm thick and is rarely seen in the lateral chest radiograph. Pericardial effusion separates the two pericardial layers and is seen as a band outlined by the mediastinal fat anteriorly and the epicardial fat posteriorly (Figs. 1 and 2). Sometimes we only see the epicardial fat displaced posteriorly, a sign that the right ventricle does not reach the anterior wall due to the fluid in the pericardial sac (Fig. 3).

Importance of the sign: It is the most reliable plain film sign of pericardial effusion and is an indication for a confirmatory ultrasound study.

The pericardial band sign is especially useful when the appearance of the heart in the PA film is not typical of pericardial effusion (Fig. 2) or when the cardiac silhouette suggests another condition (Fig. 3).

Enhanced axial CT shows the pericardial space invaded by metastasis (C, arrow). The sagittal view nicely depicts the pericardial band, outlined posteriorly by epicardial fat (D, arrow).

QUIZ: 48-year-old man with cough.

What is the probability of malignancy?
1. Low
2. 50/50
3. High
4. Can’t tell

Findings: PA radiograph shows increased density of the right hilum (A, arrow), caused by superimposition of a nodule, clearly visible in the lateral view (B, arrow). The lateral view also shows a hilar donut sign (B, red arrows), which is indicative of enlarged lymph nodes. A lung nodule plus lymph nodes suggests a high probability of malignancy.

Enhanced axial CT shows a rounded nodule (C, white arrow) accompanied by subcarinal adenopathy (C, red arrow). PET-CT confirms high uptake of both lesions (D, arrows).

Diagnosis: carcinoma with metastasis to subcarinal lymph nodes

The donut sign is visible only in the lateral view. In a normal lateral chest radiograph, the right and left pulmonary arteries are visualized in front of and behind the trachea and LUL bronchus, simulating a horseshoe (A and B, arrows). The presence of subcarinal lymphadenopathy fills the inferior portion of the ‘‘horseshoe’’, forming a circle and creating a rounded opacity in the shape of a donut (C, arrows).

Importance of this sign: suggests enlarged lymph nodes and is an indication for enhanced CT for confirmation

The donut sign is helpful when hilar enlargement is not clear in the PA view, whereas obvious lympadenopathy is seen in the lateral view (Fig. 5).

The donut sign is very helpful for distinguishing between large hila due to enlarged pulmonary arteries and hilar enlargement secondary to lymphadenopathy (Fig. 6).

Lateral views show enlarged right and left pulmonary arteries in the first case (C, arrows), secondary to pulmonary arterial hypertension. The second case shows an obvious donut sign (D, arrows), due to enlarged lymph nodes in a patient with lymphoma.

QUIZ: 67-year-old oncologic patient with shortness of breath. What do you see?

Findings: aside from the lung changes, there is a protrusion of the aortic knob (A, red arrow), known as aortic nipple. In addition, there is azygos vein enlargement, visible in the PA and lateral views (A and B, white arrows).

Unenhanced coronal CT shows a large azygos vein (C, arrow) and the aortic nipple at the aortic knob (C, red arrow). Axial CT shows the enlarged azygos (D, white arrow) and the left superior intercostal vein circling the aortic knob (aortic nipple) (D, red arrow).
Axial CT of the abdomen depicts a collapsed IVC with calcium inside (E, arrow).

Diagnosis: thrombosis of IVC with azygos and hemiazygos acting as collateral channels

The term aortic nipple refers to a small protrusion of the contour of the aortic knob, visible in up to 10% of PA radiographs. It is caused by the left superior intercostal vein, which connects with the hemiazygos vein, circling around the aortic arch. Normal size is around 1-2 mm (A and B, arrows). A large nipple suggests increased flow in the left hemiazygos system (C and D, arrows).

Importance of this sign: An enlarged aortic nipple indicates increased flow in the azygos/hemiazygos system, related to impaired circulation of the inferior or superior vena cava. This may occur in congenital interruption of the SVC or IVC, or be secondary to acquired thrombosis. These options should be investigated with enhanced CT.

Usually, the azygos vein carries more flow than the hemiazygos. Lack of enlargement of the azygos in the PA view accompanied by a large aortic nipple suggests congenital absence of the azygos vein (Fig. 7).

Occasionally, a small aneurysm of the aortic knob may simulate an aortic nipple. The correct diagnosis should be established with enhanced CT (Fig. 8).

Follow Dr. Pepe’s advice:

1. The pericardial band sign is highly reliable to suspect pericardial effusion in the lateral chest radiograph.

2. The donut sign is very useful to diagnose mediastinal lymphadenopathy.

3. The nipple sign is a good indicator of impaired flow in the SVC or IVC, either congenital or acquired.