User:Waynengo/Mediastinal shift

Hemothorax

Hemothorax, or accumulation of blood in the pleural space can result from trauma or surgical procedures in the chest. This accumulation of blood can grow large enough to compress the lung and push away other structures in the chest, thus causing a mediastinal shift. On a chest x-ray, a hemothorax can appear similarly to a pleural effusion with blunting of the pleural recess and white out of normal lung zones. In the setting of traumatic chest injury, rib fractures are also commonly observed on x-ray.

Massive right sided pleural effusion later confirmed to be a hemothorax

Masses

Masses such as tumors can also cause compression and displacement of mediastinal structures. There are various mediastinal tumors and they are classified by their location in the chest. Notable examples include include germ cell tumors and lymphomas. Teratomas are a class of germ cell tumors that arise in the chest due to failure of germ cell migration during development. They can expand to large sizes and cause hemopytsis and pleural effusion. Radiographic features of teratomas typically include fluid and fat but also muscle, teeth, and bones inside the mass.

Infection

Mediastinitis

An infection or inflammation of the mediastinum is referred to as mediastinitis. Etiologies include trauma, esophageal rupture, thoracic surgery, and descending infection from the oropharynx. Notably, post-operative mediastinitis is regarded as the most common etiology. An infection of the thoracic cavity is life threatening and therefore requires urgent diagnosis and treatment. Typical chest x-ray signs include mediastinal widening, pneumomediastinum, and pleural effusion. Computed tomography or magnetic resonance imaging are often used to get a fuller picture of the infection.

Empyema

An empyema is a collection of pus inside the pleural cavity. It is a complication of pneumonia or thoracic injury or surgery and also requires urgent diagnosis and treatment. Radiographic appearance is similar to that of a pleural effusion with costophrenic angle blunting and white out of lung zones. CT imaging is necessary to evaluate the structure of the empyema and evaluate for loculation or separation of the pus into different compartments. Finally, ultrasound is becoming a more commonly used imaging technique to evaluate an empyema. Ultrasound is more readily available at the bedside, is better at detecting pleural effusion, and can be used to guide thoracentesis to remove the empyema.

Atelectasis

Atelectasis is partial or collapse of a lung that is reversible. There are numerous etiologies including post-operative atelectasis, surfactant deficiency, mucus plugging, and foreign body aspiration. Notably, post-operative atelectasis is thought to be caused by general anesthesia administration. Collapse of the affected lung shifts mediastinal structure towards the same side and can be observed on chest x-ray or CT. Radiographic features include increased opacification of collapsed lung and/or tracheal shift.

Congenital

Pulmonary Hypoplasia

Fetal conditions can also cause mediastinal shift during development. For example, pulmonary hypoplasia is the underevelopment of a lung due to various etiologies. These include agenesis due to gene mutation, fetal hydrothorax, and congenital diaphragmatic hernia. These conditions lead to incomplete development lung tissue or hypoplasia. This can be unilateral or bilateral and is seen on x-ray as a mediastinal shift towards the side of the underdeveloped lung. Additionally, mediastinal shifts can also be detected using antenatal ultrasonography.

Pectus Excavatum

This condition is often referred to as "funnel chest" and is observed as depression of the anterior chest at the xiphisternum. Pectus excavatum is commonly unilateral and therefore can lead to asymmetric distribution of thoracic organs. Therefore, a mediastinal shift can be seen in severe cases. Radiographic features include a leftward deviation of the heart and deformed third to seventh ribs. Patients often present with exercise tolerance, cardiac arrythmias, and heart murmur.