"Widened mediastinum/mediastinal widening" is where the mediastinum has a width greater than 6 cm on an upright PA chest X-ray or 8 cm on supine AP chest film.

A widened mediastinum can be indicative of several pathologies:

- aortic aneurysm

- aortic dissection

- aortic unfolding

- aortic rupture

- hilar lymphadenopathy

- anthrax inhalation - a widened mediastinum was found in 7 of the first 10 victims infected by anthrax ("Bacillus anthracis") in 2001.

- esophageal rupture - presents usually with pneumomediastinum and pleural effusion. It is diagnosed with water-soluble swallowed contrast.

- mediastinal mass

- mediastinitis

- cardiac tamponade

- pericardial effusion

- thoracic vertebrae fractures in trauma patients.

The mediastinum (from Medieval Latin "mediastinus", "midway") is the central compartment of the thoracic cavity surrounded by loose connective tissue, as an undelineated region that contains a group of structures within the thorax. The mediastinum contains the heart and its vessels, the esophagus, trachea, phrenic and cardiac nerves, the thoracic duct, thymus and lymph nodes of the central chest.

Hemothorax tends to occur following blunt or penetrating trauma to the thorax or thoracoabdominal area. It may also follow thoracic surgery, or may be spontaneous. Chest pain, dyspnea, and tachypnea are common presenting features. Other symptoms of hemothorax are dependent on the mechanism of injury, but may include:

- Cyanosis

- Decreased or absent breath sounds on affected side

- Tracheal deviation to unaffected side

- Dull resonance on percussion

- Unequal chest rise

- Tachycardia

- Hypotension

- Pale, cool, clammy skin

- Possible subcutaneous emphysema

- Narrowing pulse pressure

The mediastinum is the cavity that separates the lungs from the rest of the chest. It contains the heart, esophagus, trachea, thymus, and aorta. The mediastinum has three main parts: the anterior mediastinum (front), the middle mediastinum, and the posterior mediastinum (back).

The most common mediastinal masses are neurogenic tumors (20% of mediastinal tumors), usually found in the posterior mediastinum, followed by thymoma (15-20%) located in the anterior mediastinum.

Masses in the anterior portion of the mediastinum can include thymoma, lymphoma, pheochromocytoma, germ cell tumors including teratoma, thyroid tissue, and parathyroid lesions. Masses in this area are more likely to be malignant than those in other compartments.

Masses in the posterior portion of the mediastinum tend to be neurogenic in origin, and in adults tend to be of neural sheath origin including neurilemomas and neurofibromas.

Lung cancer typically spreads to the lymph nodes in the mediastinum.

A hemothorax is a type of pleural effusion in which blood accumulates in the pleural cavity. This excess fluid can interfere with normal breathing by limiting the expansion of the lungs. The term is from "" + "thorax".

In several editions of Physical Diagnosis, concerning mediastinal tumors the author writes:

Many signs and symptoms of a mediastinal tumor do not distinguish between these two principal classes of mediastinal tumor. However, on a radiograph usually the former class will have an irregular shape and the latter class will have a smooth spherical or ovoid shape. A large minority of patients with a mediastinal teratoma (including dermoid cyst) will cough up hair. For a differential diagnosis, the key is to exclude aneurism.

Signs and symptoms may include stiff neck (limited neck mobility or torticollis), some form of palpable neck pain (may be in "front of the neck" or around the Adam's Apple), malaise, difficulty swallowing, fever, stridor, drooling, croup-like cough or enlarged cervical lymph nodes. Any combination of these symptoms should arouse suspicion of RPA.

The main symptom is usually severe central chest pain. Other symptoms include laboured breathing, voice distortion (as with helium) and subcutaneous emphysema, specifically affecting the face, neck, and chest. Pneumomediastinum can also be characterized by the shortness of breath that is typical of a respiratory system problem. It is often recognized on auscultation by a "crunching" sound timed with the cardiac cycle (Hamman's crunch).

Pnemomediastinum may also present with symptoms mimicking cardiac tamponade as a result of the increased intrapulmonary pressure on venous flow to the heart.

Pneumomediastinum (from Greek "pneuma" – "air", also known as mediastinal emphysema) is (abnormal presence of air or other gas) in the mediastinum. First described in 1819 by René Laennec, the condition can result from physical trauma or other situations that lead to air escaping from the lungs, airways, or bowel into the chest cavity.

Retropharyngeal abscess (RPA) is an abscess located in the tissues in the back of the throat behind the posterior pharyngeal wall (the retropharyngeal space). Because RPAs typically occur in deep tissue, they are difficult to diagnose by physical examination alone. RPA is a relatively uncommon illness, and therefore may not receive early diagnosis in children presenting with stiff neck, malaise, difficulty swallowing, or other symptoms listed below. Early diagnosis is key, while a delay in diagnosis and treatment may lead to death. Parapharyngeal space communicates with retropharyngeal space and an infection of retropharyngeal space can pass down behind the esophagus into the mediastinum. RPAs can also occur in adults of any age.

RPA can lead to airway obstruction or sepsis – both life-threatening emergencies. Fatalities normally occur from patients not receiving treatment immediately and suffocating prior to knowing that anything serious was wrong.

Symptoms include hemoptysis, and/or massive hemorrhage which result from the formation of a fistula between the trachea and the brachiocephalic artery. The primary threat is respiratory compromise leading to dyspnea and cyanosis. Patients can later present with hypovolemic shock which include symptoms of tachycardia, cyanosis, cold and clammy skin, dizziness, confusion, and fatigue. Patients may also develop septicemia.

Two-thirds of TIF occurs within three weeks of a tracheotomy. A TIF should be on the top of the differential diagnosis in patients with a tracheostomy followed by bleeding. Most effective diagnostic tool is a rigid bronchoscopy, although this may be unnecessary as a massive arterial hemorrhage from the tracheostomy likely indicates the formation of an TIF. However, a rigid brochoscopy can clear the tracheobronchial tree of aspirated blood and may be used to terminate blood flow.

Only 35% of TIF patients exhibit the pathognomonic warning signs which include sentinel bleeding, a small bleed from the tracheostomy in the preceding the TIF, and pulsations of the tracheostomy tube that coincides with the heartbeat.

Flail chest is a life-threatening medical condition that occurs when a segment of the rib cage breaks due to trauma and becomes detached from the rest of the chest wall. Two of the symptoms of flail chest are chest pain and shortness of breath.

It occurs when multiple adjacent ribs are broken in multiple places, separating a segment, so a part of the chest wall moves independently. The number of ribs that must be broken varies by differing definitions: some sources say at least two adjacent ribs are broken in at least two places, some require three or more ribs in two or more places. The flail segment moves in the opposite direction to the rest of the chest wall: because of the ambient pressure in comparison to the pressure inside the lungs, it goes in while the rest of the chest is moving out, and vice versa. This so-called "paradoxical breathing" is painful and increases the work involved in breathing.

Flail chest is usually accompanied by a pulmonary contusion, a bruise of the lung tissue that can interfere with blood oxygenation. Often, it is the contusion, not the flail segment, that is the main cause of respiratory problems in people with both injuries.

Surgery to fix the fractures appears to result in better outcomes.

Two of the symptoms of flail chest are chest pain and shortness of breath.

The characteristic paradoxical motion of the flail segment occurs due to pressure changes associated with respiration that the rib cage normally resists:

- During normal inspiration, the diaphragm contracts and intercostal muscles pull the rib cage out. Pressure in the thorax decreases below atmospheric pressure, and air rushes in through the trachea. The flail segment will be pulled in with the decrease in pressure while the rest of the rib cage expands.

- During normal expiration, the diaphragm and intercostal muscles relax increasing internal pressure, allowing the abdominal organs to push air upwards and out of the thorax. However, a flail segment will also be pushed out while the rest of the rib cage contracts.

The constant motion of the ribs in the flail segment at the site of the fracture is extremely painful, and, untreated, the sharp broken edges of the ribs are likely to eventually puncture the pleural sac and lung, possibly causing a pneumothorax. The concern about "mediastinal flutter" (the shift of the mediastinum with paradoxical diaphragm movement) does not appear to be merited. Pulmonary contusions are commonly associated with flail chest and that can lead to respiratory failure. This is due to the paradoxical motions of the chest wall from the fragments interrupting normal breathing and chest movement. Typical paradoxical motion is associated with stiff lungs, which requires extra work for normal breathing, and increased lung resistance, which makes air flow difficult. The respiratory failure from the flail chest requires mechanical ventilation and a longer stay in an intensive care unit. It is the damage to the lungs from the flail segment that is life-threatening.

The symptomatic patient may present with dyspnea, cyanosis, chest pain, pulsus paradoxus, bradycardia or tachycardia. On physical examination, the patient may have the classic “Beck’s triad” – hypotension, raised JVP and distant heart sounds, when complicated by cardiac tamponade. Extension of the mediastinal air to the subcutaneous tissues via the fascial planes may lead to subcutaneous emphysema. When air and fluid mix together in the pericardial sac, a tinkling sound superimposed over a succussion splash is heard. This is known as a “Bruit de Moulin”, which is French for “Mill–wheel” murmur. Air between the anterior parietal pericardium and the thoracic cage may also give rise to the “Hamman’s Sign” – which is a crunching sound typically heard on auscultation of the chest, but may sometimes be heard even with the unaided ear.

Symptoms may include coughing, an upper respiratory tract infection, shortness of breath, and chest pain. These symptoms are very non-specific, and can be caused by other types of tumor in the lung or mediastinum more generally, and by other conditions. Imaging (X-ray, CT, MRI) may be used to determine the presence and precise location of a tumor, but not a specific diagnosis of PPB or other tumor.

Doctors are unable to tell if a child has PPB right away, and not upper respiratory tract infection, until more test are taken and they show that there is no infection. Another symptom is pneumothorax.

An abscess of the thymus (also known as "Dubois' abscesses") is a condition that is one of many possible causes of cysts in the mediastinum.

It can present with chest pain behind the sternum.

It can be associated with congenital syphilis.

Although the thymus is usually classified with the immune system, thymic diseases are classified with endocrine disorders in ICD-9 and ICD-10.

Woodring et al. (1991) suggested the following diagnostic criteria for tracheomegaly in adults based on chest radiography:

- Adult Males: Tracheal transverse diameter > 25 mm and sagittal diameter > 27 mm.

- Adult Females: Tracheal transverse diameter > 21 mm and sagittal diameter > 23 mm.

Pneumopericardium is a medical condition where air enters the pericardial cavity. This condition has been recognized in preterm neonates, in which it is associated with severe lung pathology, after vigorous resuscitation, or in the presence of assisted ventilation. This is a serious complication, which if untreated may lead to cardiac tamponade and death. Pneumomediastinum, which is the presence of air in the mediastinum, may mimic and also coexist with pneumopericardium.

It can be congenital, or introduced by a wound.

Mediastinitis is inflammation of the tissues in the mid-chest, or mediastinum. It can be either acute or chronic.

Acute mediastinitis is usually bacterial and due to rupture of organs in the mediastinum. As the infection can progress rapidly, this is considered a serious condition. Chronic sclerosing (or fibrosing) mediastinitis, while potentially serious, is caused by a long-standing inflammation of the mediastinum, leading to growth of acellular collagen and fibrous tissue within the chest and around the central vessels and airways. It has a different cause, treatment, and prognosis than acute infectious mediastinitis.

Space Infections : Pretracheal space - lies anterior to trachea. Pretracheal space infection leads to mediastinitis. Here, the fascia fuses with the pericardium and the parietal pleura , which explains the occurrence of empyema and pericardial effusion in mediastinitis.

Chronic mediastinitis is usually a radiologic diagnosis manifested by diffuse fibrosis of the soft tissues of the mediastinum. This is sometimes the consequence of prior granulomatous disease, most commonly histoplasmosis. Other identifiable causes include tuberculosis, IgG4-related disease and radiation therapy. Fibrosing mediastinitis most frequently causes problems by constricting blood vessels or airways in the mediastinum. This may result in such complications as superior vena cava syndrome or pulmonary edema from compression of pulmonary veins.

Treatment for chronic fibrosing mediastinitis is somewhat controversial, and may include steroids or surgical decompression of affected vessels.

The classic history of esophageal rupture is one of severe retching and vomiting followed by excruciating retrosternal chest and upper abdominal pain. Odynophagia, tachypnea, dyspnea, cyanosis, fever, and shock develop rapidly thereafter.

Physical examination is usually not helpful, particularly early in the course. Subcutaneous emphysema (crepitation) is an important diagnostic finding but is not very sensitive, being present in only 9 of 34 patients (27 percent) in one series. A pleural effusion may be detected.

Mackler's triad includes chest pain, vomiting, and subcutaneous emphysema, and while it is a classical presentation, it is only present in 14% of people.

Pain can occasionally radiate to the left shoulder, causing physicians to confuse an esophageal perforation with a myocardial infarction.

It may also be audibly recognized as Hamman's sign.

Common misdiagnoses include myocardial infarction, pancreatitis, lung abscess, pericarditis, and spontaneous pneumothorax. If esophageal perforation is suspected, even in the absence of physical findings,chest xray, water soluble contrast radiographic studies of the esophagus and a CT scan should be promptly obtained. In most cases, non-operative management is administered based on radiological evidence contained in mediastinal collection.

Tracheobronchomegaly is a very rare congenital disorder of the lung primarily characterized by an abnormal widening of the upper airways. The abnormally widened trachea and mainstem bronchi are associated with recurrent lower respiratory tract infection and copious purulent sputum production, eventually leading to bronchiectasis and other respiratory complications.

Signs and symptoms of spontaneous subcutaneous emphysema vary based on the cause, but it is often associated with swelling of the neck and chest pain, and may also involve sore throat, neck pain, difficulty swallowing, wheezing and difficulty breathing. Chest X-rays may show air in the mediastinum, the middle of the chest cavity. A significant case of subcutaneous emphysema is easy to detect by touching the overlying skin; it feels like tissue paper or Rice Krispies. Touching the bubbles causes them to move and sometimes make a crackling noise. The air bubbles, which are painless and feel like small nodules to the touch, may burst when the skin above them is palpated. The tissues surrounding SCE are usually swollen. When large amounts of air leak into the tissues, the face can swell considerably. In cases of subcutaneous emphysema around the neck, there may be a feeling of fullness in the neck, and the sound of the voice may change. If SCE is particularly extreme around the neck and chest, the swelling can interfere with breathing. The air can travel to many parts of the body, including the abdomen and limbs, because there are no separations in the fatty tissue in the skin to prevent the air from moving.