Mediastinitis

What the mediastinum is

The mediastinum is the central compartment of the chest, between the two lungs, running from the base of the neck to the diaphragm. It contains the heart, aorta and great veins, the windpipe and main airways, the esophagus, the thymus gland, lymph nodes and nerves. These are packed in loose connective tissue that is continuous with tissue planes in the neck, so infection can spread quickly from the neck into the chest.

Causes and types

Acute mediastinitis

Post-sternotomy mediastinitis affects roughly 1 to 2% of people after open-heart surgery. Risk factors include diabetes, obesity, smoking, COPD, use of both internal mammary arteries for bypass, prolonged surgery and re-operation. Staphylococcus aureus (including MRSA) and skin bacteria are the usual causes.

Esophageal perforation is the most dangerous source because gut bacteria and digestive contents spread rapidly.

Descending necrotizing mediastinitis usually starts from a dental abscess or deep neck infection, often a lower molar infection. It involves mixed mouth bacteria, including anaerobes.

Chronic fibrosing mediastinitis

A rare, slowly progressive condition in which excess scar tissue builds up in the mediastinum. In the US it is mostly an abnormal immune reaction to past histoplasmosis infection, a fungus common in the Ohio and Mississippi River valleys. Tuberculosis, other fungi and some autoimmune conditions can also cause it. The scarring can compress the superior vena cava, pulmonary arteries and veins, airways or esophagus.

Symptoms

Acute mediastinitis

• Fever and chills
• Chest pain behind the breastbone, which may spread to the neck or back
• Fast heart rate and fast breathing
• Pain or difficulty swallowing
• Crackling under the skin of the neck or chest (air from an esophageal tear)
• After heart surgery: wound redness, drainage of pus, or a breastbone that moves or clicks
• Neck swelling, stiffness and redness with descending infection
• Signs of sepsis: confusion, low blood pressure, low urine output

Fibrosing mediastinitis

• Cough, breathlessness and coughing blood
• Recurrent chest infections
• Swelling of the face, neck and arms with visible chest veins (superior vena cava syndrome)
• Difficulty swallowing

How it is diagnosed

• CT scan of the chest (and neck when the source is above): shows fluid collections, gas, abscesses and their extent. It is the key test.
• Blood tests: white cell count, inflammation markers, blood cultures.
• Contrast swallow or endoscopy to locate an esophageal tear.
• Sampling fluid from the wound or collection to identify the bacteria.
• For fibrosing mediastinitis: CT showing calcified tissue, plus tests for histoplasmosis and sometimes a biopsy to exclude cancer or lymphoma.

Treatment

Acute mediastinitis

• Broad-spectrum IV antibiotics started immediately, covering staphylococci (including MRSA where relevant), gut and mouth bacteria and anaerobes, then adjusted to culture results. Antifungals may be added for esophageal leaks.
• Surgical drainage and debridement: opening and cleaning the infected space, removing dead tissue and infected wires or bone. Approaches include reopening the sternotomy, neck incisions, chest tube drainage, or thoracotomy or video-assisted thoracoscopic surgery.
• Negative-pressure wound therapy (vacuum dressings) is widely used for sternal wounds before closure, often with muscle flaps to rebuild the chest wall.
• Repair of the source: suturing or stenting an esophageal tear, or draining the neck abscess.
• Intensive care support for breathing, blood pressure and nutrition.

Fibrosing mediastinitis

There is no reliably effective drug treatment. Antifungals and steroids help only in selected cases. Stents are used to open compressed veins, arteries or airways, and surgery is reserved for specific complications.

Outlook

Acute mediastinitis remains serious. Death rates vary by cause, highest after esophageal perforation, and depend greatly on how quickly drainage and antibiotics start. Post-sternotomy mediastinitis also lengthens hospital stays and affects long-term survival. Fibrosing mediastinitis progresses slowly, and the outlook depends on which structures become compressed.

Prevention

• Before heart surgery: stop smoking, control blood sugar, and follow skin decolonization and antiseptic washing instructions.
• After heart surgery: follow sternal precautions (avoid heavy lifting and pushing with the arms for several weeks) and report wound changes promptly.
• Get prompt treatment for dental infections and severe sore throats with neck swelling.

Frequently asked questions

What causes mediastinitis?

Most acute cases are caused by infection after open-heart surgery, a tear in the esophagus from vomiting, endoscopy or a swallowed object, or a dental or neck infection spreading down into the chest. Chronic fibrosing mediastinitis is usually a reaction to past histoplasmosis infection.

What are the first signs of mediastinitis?

Early signs include fever, chills, chest pain behind the breastbone, a fast heart rate and difficulty or pain when swallowing. After heart surgery, redness, drainage or instability of the breastbone wound can be the first warning. Anyone with these symptoms needs emergency assessment.

Is mediastinitis fatal?

It can be. Acute mediastinitis is life-threatening, especially after esophageal perforation, and outcomes depend heavily on speed of treatment. With early CT diagnosis, IV antibiotics and surgical drainage, many people recover, though hospital stays are often long.

How common is mediastinitis after open-heart surgery?

It affects roughly 1 to 2% of people who have surgery through the breastbone. The risk is higher with diabetes, obesity, smoking, lung disease, prolonged surgery and re-operation. Careful preparation and wound care lower the risk.

What is fibrosing mediastinitis?

It is a rare, chronic condition in which scar tissue gradually builds up in the center of the chest, often after histoplasmosis. The scarring can squeeze blood vessels, airways or the esophagus, causing breathlessness, cough, coughing blood or swelling of the face and arms.