Chest Imaging: Pleural Syndromes

• The presentation is about chest imaging, part II, and covers pleural syndromes, nodules and pulmonary masses, pulmonary embolism, congestive heart failure, hypertensive heart disease, and thoracic emergencies.

Síndromes Pleurales

• Covers the topic of pleural syndromes.

Derrame Pleural

• Pleural effusion involves the accumulation of liquid (exudate/transudate) in the pleural cavity between the parietal and visceral pleura.
• Radiographic signs of pleural effusion include dense homogeneous opacity.
• Other signs include loss of the costophrenic angle.
• Effusions create a meniscus appearance (higher laterally than medially.
• Hemidiaphragm is often blurred.
• Effusions will lack an air bronchogram.
• The minimum detectable amount of fluid in AP/PA view is 200 ml.
• The minimum detectable amount of fluid in lateral view is 75 ml.
• When a pleural effusion is free, it follows gravity (gravity-dependent).
• In decubitus position, the liquid accumulates in the posterior portion.
• Radiographic signs of pleural effusions in decubitus include opacification of the affected lung field, with blurring of pulmonary vessels, and decreased inspiratory lung volume.
• CT scans show liquid density with no pulmonary parenchyma present.
• Water density is approximately -5 to +5 Hounsfield units (HU).
• Transudate density is approximately 16 to 20 HU.
• Exudate density is approximately 20 to 30 HU.

Empiema

• Empyema is defined as an infectious and purulent pleural effusion.
• Empyemas are usually loculated.
• Neumococo is associated with pediatric empyemas.
• Staph. aureus, gram-negative bacteria, anaerobes, and TB are related to adult empyemas.
• Radiographic aspects are similar to derrame but are usually unilateral/asymmetric, with obtuse angles and a lenticular shape.
• CT Scans show liquid collection with a contrast-enhancing capsule and possible air inside.

Hemotórax

• A hemothorax is blood in the pleural space.
• Radiographically, a hemothorax appears similarly to a pleural effusion.
• On CT, acute hemothorax presents as a hypodense collection of fresh blood or a hyperdense collection of clotted blood.
• Hemothoraces are usually caused by trauma, either penetrating or blunt force trauma to the parietal or visceral pleura.
• Bleeding into the cavity can be massive, with one hemithorax holding 30-40% of the total blood volume.
• Other less common causes include pneumothorax, pulmonary infarction, and anticoagulation therapy.

Neumotórax

• Pneumothorax is the presence of air accumulation in the pleural cavity between the parietal and visceral pleura.
• Radiographically, they are detected by the presence of a pleural line (the edge of the lung delimited by air).
• Lung markings/vessels are absent distal to the pleural line.
• In supine patients the "deep sulcus sign" on AP films can be indicative of pneumothorax.
• Other supine findings include asymmetry of the lateral costophrenic angles with increased depth and radiolucency.
• The air collection extends to the hypochondrium with a triangular or crescent shape.
• On CT, pneumothorax appears as an immediate identification with air density (completely black).
• Utilize pulmonary windows on CT scans.

Derrame Pericárdico

• Pericardial effusion.
• Diagnostic modalities include TAC (CT), ECO (USG), and RM (MRI).

Pericardio: Derrame

• Etiologies of pericardial effusion include myocardial infarction with left-sided heart failure.
• Additional etiologies are uremia (50% in chronic kidney disease), viral or TB infection, trauma, autoimmune diseases such as rheumatoid arthritis, lupus, and systemic sclerosis.
• The cavity can hold up to 1 liter of fluid without tamponade.
• Signs of tamponade include higher respiratory systemic circulation (RSCs), distension of neck veins, increased intrapericardial pressure and cardiac compression, decreased intracardiac volume, decreased diastolic filling pressure, and decreased cardiac output (CO).
• On PA/AP chest X-rays, moderate effusions (>250ml) may show the “cantimplora” sign, a globular cardiac silhouette, and a higher mediastinum.
• On lateral X-rays, the "Oreo cookie" sign may be seen, referring to water density >2mm between retrosternal and sub-epicardial fat.