Necrotizing Pneumonia and Pulmonary Gangrene

Spectrum of Disease

Lung Abscess (see Lung Abscess)
Necrotizing Pneumonia: pulmonary inflammation with alveolar filling (consolidation), peripheral necrosis, and multiple small cavities
- Compromise of Bronchial and Pulmonary Vascular Supply: leads to devitalization of lung parenchyma and impedes antibiotic delivery -> uncontrolled infection and further destruction of lung tissue
- Necrotizing pneumonia is more commonly associated with Gram-positive organisms (Staphylococcus Aureus, Streptococcus Pneumoniae)
Pulmonary Gangrene: final stage in the continuum of progressive devitalization of pulmonary parenchyma, characterized by sloughing of a pulmonary segment or lobe
- Pulmonary gangrene is more commonly associated with Gram-negative organisms (Klebsiella, Pseudomonas), but may also occur with Gram-positive organisms (Streptococcus Pneumoniae)

Aggregatibacter Actinomycetemcomitans (Formerly Actinobacillus Actinomycetemcomitans) (see Aggregatibacter Actinomycetemcomitans)
Actinomycosis (see Actinomycosis)
Anaerobes (see Aspiration Pneumonia)
Clostridium Perfringens (see Clostridium Perfringens)
Haemophilus (see Haemophilus)
- Epidemiology: less common etiology
Invasive Pulmonary Aspergillosis (see Invasive Aspergillosis)
Klebsiella (see Klebsiella)
- Epidemiology: less common etiology
Mycobacterium Chelonae (see Mycobacterium Chelonae])
Mycobacterium Tuberculosis (see Tuberculosis)
- Epidemiology: may occur in some cases
Mycoplasma (see Mycoplasma Pneumoniae)
Pseudomonas Aeruginosa (see Pseudomonas Aeruginosa)
- Epidemiology: less common etiology
Q Fever (see Q Fever)
Staphylococcus Aureus (see Staphylococcus Aureus)
- Epidemiology
  - Common Etiology
- Particularly Panton-Valentine Leukocidin (PVL) Toxin-Producing Strains
  - PVL Toxin is Known to Cause Necrotizing Pneumonia with Rapid Progression to Respiratory Failure/Shock and is Associated with a High Mortality Rate
Streptococcus Pneumoniae (Pneumococcus) (see Streptococcus Pneumoniae)
- Epidemiology: common etiology

Unkown Why Same Species of Organism Causes Necrotizing Pneumonia in One Host and Non-Necrotizing Pneumonia in Another Host
- May be related to overall health/immune status of host, hsot inflammatory response, development of localized vasculitis with thrombosis of small and large vessels, siz of inoculum, virulence and antibiotic resistance pattern of pathogen, or a delay in seeking medical care

Chest CT is the Best Imaging Modaility to Diagnose Necrotizing Pneumonia (and Pulmonary Gangrene)
Findings
- Patchy Lung Inflammation with Lack of Perfusion: with lack of contrast uptake by the parenchyma
- Microabscesses: may coalesce to form larger cavities (and may progress to frank pulmonary gangrene)
Radiographic Criteria for Pulmonary Gangrene (with Chest CT with IV Contrast)
- “Air Crescent Sign”: movable mass of devitalized tissue within the cavity
- Bronchial Obstruction: may also be present
- Obliteration of the Pulmonary Arterial Supply to a Segment/Lobe Containing Large Cavities and Necrotic Parenchyma (Especially when Necrosis Affects >50% of the Involved Lobe)

Antibiotic Choice Needs to Be Guided by Early Identification of Organism: including antibiotic sensitivities

Indicated for Cases with Associated Complicated Parapneumonia Effusion/Empyema

Contraindicated: due to inability to adequately debride necrotic lung parenchyma, rapid catheter obstruction (which are not amenable to the use of thrombolytics into the lung parenchyma), and the significantly increased risk of creation of a difficult to manage bronchopleural fistula

Indications
- Massive Hemoptysis
- Necrotizing Pneumonia Unresponsive to Medical Therapy
- Pulmonary Gangrene
Optimal Timing of Surgery is Unclear

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Necrotizing Pneumonia Caused by Mixed Infection with Actinobacillus actinomycetemcomitans and Actinomyces israelii: Case Report and Review. Clin Infect Dis. (1994) 18 (3): 450-452
Necrotizing pneumonia in bacteraemic pneumococcal infection. British Journal of Diseases of the Chest Volume 80, 1986, Pages 295-296
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Management of necrotizing pneumonia and pulmonary gangrene: A case series and review of the literature. Can Respir J. 2014 Jul-Aug; 21(4): 239–245 [MEDLINE]