Mediastinitis

Mediastinitis refers to an infection or inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation involving the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels (a region in the thoracic cavity containing the heart, thymus gland, portions of the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus, and trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea). Acute mediastinitis can be caused by bacterial infection due to direct contamination, hematogenous or lymphatic spread, or extension of infection from nearby structures. Chronic mediastinitis, also known as fibrosing mediastinitis, is commonly related to chronic inflammatory conditions that cause the proliferation of connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue. Mediastinitis is treated with broad-spectrum antibiotics and surgery, as well as supportive care, depending on the etiology. Mortality from this condition is high.

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Anatomy and Etiology

Anatomy

Mediastinum:

  • Central compartment of thoracic cavity bordered by:
    • Lung pleural sacs laterally
    • Thoracic outlet above
    • Diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm below
  • Structures inside mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels:
    • Heart
    • Thymus
    • Great vessels (vena cava, aorta, pulmonary arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries)
    • Esophagus
    • Distal portion of trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea
    • Mainstem bronchi
    • Phrenic nerve
    • Vagus nerve (cranial nerve (CN) 10)
Mediastinum

Three-dimensional rendering of high-resolution CT identifying the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels:
The area highlighted in blue is the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels. This area is bordered by the lung pleural sacs laterally, the thoracic outlet above, and the diaphragm below. The structures contained in the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels include the heart, thymus, great vessels (vena cava, aorta, pulmonary arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries), esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus, distal portion of trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea, mainstem bronchi, and phrenic and vagus nerves.

Image: “Mediastinum” by Mikael Häggström. License: CC0

Etiology

Acute mediastinitis:

  • Esophageal perforation Esophageal perforation Esophageal rupture or perforation is a transmural defect that occurs in the esophagus, exposing the mediastinum to GI content. The most common cause of esophageal perforation is iatrogenic trauma by instrumentation or surgical procedures. Esophageal Perforation:
    • Most common cause: 90%
    • History of severe vomiting 
    • Hematemesis
    • Sudden-onset neck pain Neck Pain Neck pain is one of the most common complaints in the general population. Depending on symptom duration, it can be acute, subacute, or chronic. There are many causes of neck pain, including degenerative disease, trauma, rheumatologic disease, and infections. Neck Pain and swelling
    • Painful swallowing
  • Postoperative mediastinitis:
    • One of the most common causes
    • 1%–2% of cardiac surgeries
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain, purulent or erythematous chest wound
    • Most patients present within 1 month of surgery.
  • Descending necrotizing mediastinitis:
    • Usually direct extension ( retropharyngeal abscess Retropharyngeal abscess Retropharyngeal abscesses occur in the retropharyngeal space, which extends from the base of the skull to the posterior mediastinum. The abscesses occur due to extension of local infections, including upper respiratory infections or localized infections from trauma such as dental procedures. Retropharyngeal Abscess, tonsillitis Tonsillitis Tonsillitis is inflammation of the pharynx or pharyngeal tonsils, and therefore is also called pharyngitis. An infectious etiology in the setting of tonsillitis is referred to as infectious pharyngitis, which is caused by viruses (most common), bacteria, or fungi. Tonsillitis, pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis, epiglottitis Epiglottitis Epiglottitis (or "supraglottitis") is an inflammation of the epiglottis and adjacent supraglottic structures. The majority of cases are caused by bacterial infection. Symptoms are rapid in onset and severe. Epiglottitis)
    • Worsening sore throat and/or neck swelling
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain, shortness of breath
    • Has become less frequent due to antibiotic usage

Chronic mediastinitis:

Fibrosing mediastinitis:

  • Related to long-standing inflammatory conditions
  • Marked by growth of acellular collagen and fibrous tissue within chest
  • Granulomatous mediastinitis ( histoplasmosis Histoplasmosis Histoplasmosis is an infection caused by Histoplasma capsulatum, a dimorphic fungus. Transmission is through inhalation, and exposure to soils containing bird or bat droppings increases the risk of infection. Most infections are asymptomatic; however, immunocompromised individuals generally develop acute pulmonary infection, chronic infection, or even disseminated disease. Histoplasma/Histoplasmosis, tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis infections)
  • Non-granulomatous fibrosing mediastinitis (reaction to drugs or radiation therapy)
  • Autoimmune diseases (Behcet’s disease)

Diagnosis

History

  • Symptoms:
    • Cough
    • Fevers
    • Sore throat
    • Chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain 
    • Painful swallowing
    • Severe vomiting
  • History of: 
    • Recent surgery
    • Autoimmune disease

Physical exam

Acute mediastinitis:

  • “Ill appearing”
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Chills
  • Tachycardia
  • Chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Odynophagia
  • CN deficits (IX, X, XI, and XII)
  • Leukocytosis
  • Wound drainage or purulent discharge

Chronic mediastinitis:

  • Insidious progression
  • Constricted airway causes cough and shortness of breath.
  • Constricted esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus causes difficulty swallowing.
  • Constricted blood vessels cause hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis and pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain in chest.

Laboratory tests

  • CBC: elevated leukocytes (nonspecific for acute infection)
  • Inflammatory markers:
    • Elevated CRP
    • Elevated procalcitonin
  • Mediastinal aspiration:
    • Invasive
    • Allows for culturing and targeting of infectious agent 
  • Blood cultures:
    • May reveal bacterial pathogen
    • Especially postoperative cases

Imaging

  • Chest X-ray: 
    • Hilar mass
    • Widened mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels
    • Pneumomediastinum
  • CT scan: 
    • Mediastinal abscess/hilar mass
    • Swelling
    • If pericardial involvement:
      • Pericardial thickening
      • Pericardial effusion Pericardial effusion Pericardial effusion is the accumulation of excess fluid in the pericardial space around the heart. The pericardium does not easily expand; thus, rapid fluid accumulation leads to increased pressure around the heart. The increase in pressure restricts cardiac filling, resulting in decreased cardiac output and cardiac tamponade. Pericardial Effusion and Cardiac Tamponade
      • Pneumopericardium
    • Fibrosing mediastinitis
      • Calcifications
      • Infiltrating mass

Management

Acute mediastinitis:

  • Antibiotics: 
    • Initially, broad spectrum
    • Culture directed when possible
  • Surgical drainage and debridement 
  • High mortality rate (10%–50%), even with appropriate treatment

Chronic fibrosing mediastinitis:

  • Lack of consensus
  • Treat underlying condition when known.
  • Medication:
    • Immunosuppressants Immunosuppressants Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. Immunosuppressants
    • Corticosteroids
    • Antifungals
  • Surgical decompression of affected structure

Clinical Relevance

  • Retropharyngeal abscess: located behind posterior pharyngeal wall in retropharyngeal space. Usually presents with stiff neck and difficulty swallowing. Can pass from parapharyngeal to retropharyngeal space and then behind esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus into mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels. Treatment involves drainage and antibiotic administration.
  • Epiglottitis: life-threatening inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of epiglottis and surrounding structures usually secondary to bacterial infection. Symptoms are rapid in onset and severe. Can cause airway obstruction Airway obstruction Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Airway Obstruction leading to difficulty in breathing, stridor, and bluish discoloration of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin, ultimately leading to death. Diagnosis is made on direct visualization of the epiglottis by direct fiberoptic laryngoscopy in the operating room. 
  • Histoplasmosis: rare fungal infection of the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs caused by inhaling Histoplasma Histoplasma Histoplasmosis is an infection caused by Histoplasma capsulatum, a dimorphic fungus. The fungus exists as a mold at low temperatures and as yeast at high temperatures. H. capsulatum is the most common endemic fungal infection in the US and is most prevalent in the midwestern and central states along the Ohio and Mississippi River valleys. Histoplasma/Histoplasmosis capsulatum spores, often found in bat and bird droppings, which may lead to granulomatous mediastinitis. Presents with cough, shortness of breath, and difficulty breathing, accompanied by mediastinal or hilar lymph nodes (or masses), or by arthralgias and erythema nodosum Erythema nodosum Erythema nodosum is an immune-mediated panniculitis (inflammation of the subcutaneous fat) caused by a type IV (delayed-type) hypersensitivity reaction. It commonly manifests in young women as tender, erythematous nodules on the shins. Erythema Nodosum. Treatment involves antifungal medication of varied durations and strengths depending on severity of infection.
  • Tuberculosis ( TB TB Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis): disease caused by Mycobacterium Mycobacterium Mycobacterium is a genus of the family Mycobacteriaceae in the phylum Actinobacteria. Mycobacteria comprise more than 150 species of facultative intracellular bacilli that are mostly obligate aerobes. Mycobacteria are responsible for multiple human infections including serious diseases, such as tuberculosis (M. tuberculosis), leprosy (M. leprae), and M. avium complex infections. Mycobacterium tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis. Bacteria usually attack the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs, but can also affect other parts of the body. Spreads through the air when a person infected with TB TB Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis of the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs or throat talks, sneezes, or coughs. Chronic TB TB Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis infection may cause granulomatous mediastinitis.
  • Caustic ingestion Caustic Ingestion Caustic agents are acidic or alkaline substances that damage tissues severely if ingested. Alkali ingestion typically damages the esophagus via liquefactive necrosis, whereas acids cause more severe gastric injury leading to coagulative necrosis. Caustic Ingestion (Cleaning Products): Caustic agents are acidic or alkaline substances that can severely damage organic tissues. Alkali ingestion typically damages the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus, whereas acids cause more severe gastric injury. Both kinds can induce laryngeal and tracheobronchial injury. Management involves securing airways, checking breathing and circulation, decontamination (remove clothes, skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin irrigation), and endoscopy within 24 hours.
    Esophageal perforation Esophageal perforation Esophageal rupture or perforation is a transmural defect that occurs in the esophagus, exposing the mediastinum to GI content. The most common cause of esophageal perforation is iatrogenic trauma by instrumentation or surgical procedures. Esophageal Perforation:
    life-threatening condition resulting from spontaneous rupture (Boerhaave’s syndrome), iatrogenic causes (endoscopy), infectious causes, or esophageal ulcers. Present with chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain, tachypnea, and pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion. Management involves antibiotics and surgical repair. Due to its location adjacent to the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels, esophageal perforation may be complicated by acute mediastinitis.

References

  1. Kappus S, King O. Mediastinitis. (2020). StatPearls. Treasure Island (FL): StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK559266/
  2. Krüger M, Decker S, Schneider JP, Haverich A, Schega O. Therapie der akuten Mediastinitis [Surgical treatment of acute mediastinitis]. Chirurg. 2016 Jun;87(6):478-85. German. doi: 10.1007/s00104-016-0171-8.
  3. Van Wingerden JJ, de Mol BA, van der Horst CM. Defining post-sternotomy mediastinitis for clinical evidence-based studies. (2019). Asian Cardiovasc Thorac Ann 355-63. doi: 10.1177/0218492316639405.
  4. Goh SSC. Post-sternotomy mediastinitis in the modern era. (2017). J Card Surg 556-566. doi: 10.1111/jocs.13189.
  5. Patel M, Lu F, Hannaway M, Hochman K. Fibrosing mediastinitis: a rare complication of histoplasmosis Histoplasmosis Histoplasmosis is an infection caused by Histoplasma capsulatum, a dimorphic fungus. Transmission is through inhalation, and exposure to soils containing bird or bat droppings increases the risk of infection. Most infections are asymptomatic; however, immunocompromised individuals generally develop acute pulmonary infection, chronic infection, or even disseminated disease. Histoplasma/Histoplasmosis. (2015). BMJ Case Rep. doi: 10.1136/bcr-2015-212774

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