Necrotising pneumonia refers to pneumonia characterised by the development of necrosis within infected lung tissue.
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Terminology
While the term has been used synonymously with cavitating pneumonia in some publications 1, not all necrotising pulmonary infections may be complicated by cavitation.
Epidemiology
Necrotising changes may be seen in ~7% of those with bacterial pneumonia 2. It can affect patients of any age and is increasingly being reported in the paediatric population 3.
Pathology
Progression to necrotising pneumonia can occur from either virulence factors of the microorganism, predisposing factors of the host, or both.
It can result from a large number of pathogens, which include:
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Staphylococcus aureus
particularly in young immunocompetent patients 4
this ability to cause lung necrosis appears to be intimately related to the secretion of the Panton-Valentine Leukocidin (PVL); a pore-forming cytotoxin present in the majority of Meticillin-resistant Staphylococcus aureus isolates, which assembles as a ring pore in the membrane of the host leucocytes, leading to leakage of cell contents and ultimately leucocyte necrosis and a superantigen effect 5
Klebsiella pneumoniae (Klebsiella pneumonia) 6
Enterobacter spp.
Nocardia spp. (pulmonary Nocardia infection)
Actinomyces spp. (thoracic actinomyces infection)
Pseudomonas spp. (Pseudomonas aeruginosa pneumonia)
Pneumococcus spp.: especially type III Pneumococcal sp. 2
Haemophilus influenzae (pulmonary Haemophilus influenzae infection) 7
Radiographic features
CT
If a necrotising infection is suspected, contrasted CT thorax allows appreciation of areas with low attenuation and non-enhancement within the necrotic portions.
CT imaging may show distinct areas of low attenuation with decreased parenchymal enhancement (representing liquefaction 8) in all or parts of the affected area of infection (consolidation) 15.
Normal pulmonary parenchymal architecture within the necrotic segment is often lost 1.
Treatment and prognosis
Treatment depends on the underlying agent while prognosis depends on the severity of the pathogen as well as the susceptibility of the host. In general, complete recovery can be anticipated in children with bacteraemic necrotising pneumococcal pneumonia contrary to what is seen in adults 8.
As opposed to a formed lung abscess, interventional procedures (e.g. drainage) may be counterproductive in cases of necrotising pneumonia due to the likelihood of creating a bronchopleural fistula 9. In some centres, pulmonary resection has been carried out as a surgical option 10,11.
Differential diagnosis
For a lesion with large areas of low intrinsic low attenuation, consider:
lung abscess: more well-defined with little surrounding consolidation 12
necrotising pulmonary malignancy 13
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