Pulmonary fibrosis is the preferred general term for the permanent replacement of lung parenchyma by connective tissue and is typically associated with functional impairment. A variety of insults cause focal or diffuse lung injury (mechanical, infectious, inflammatory, and iatrogenic). Lung repair culminates in fibrosis with volume loss and architectural distortion.
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Terminology
In certain cases, fibrosis may be focal and may be stable over time. In others, fibrosis can be progressive and follow a recognisable CT pattern such as UIP or NSIP. Interstitial lung abnormality refers to early fibrotic lung disease which may progress.
Pathology
Fibrosis in the lung is a process that occurs in the interstitium. Pulmonary fibrosis can be localized, segmental, or lobar or affect the entirety of the lung(s). Among the many conditions associated with pulmonary fibrosis are:
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significant acute insult to the lungs
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from a significant pulmonary infection
Post COVID fibrosis, especially in patients admitted to ICU and needing intubation/ventilation
diffuse alveolar damage from any source
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inhaled substances
coal/silica: progressive massive fibrosis
asbestos: asbestos-related pulmonary fibrosis
radiation: radiation-induced pulmonary fibrosis
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congenital conditions
autoimmune conditions
connective tissue disorders
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granulomatous conditions
sarcoidosis: pulmonary manifestations of sarcoidosis
tuberculosis: pulmonary manifestations of tuberculosis
granulomatosis with polyangiitis: pulmonary manifestations of granulomatosis with polyangiitis
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others
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chronic conditions
polymyalgia rheumatica (occasional case reports 6)
medications: drug-induced lung disease
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aging
some studies report thin-section CT findings associated with interstitial lung disease to some degree are frequently seen in "asymptomatic" elderly individuals 7,8
Radiographic features
CT
Early pulmonary fibrosis 12:
irregular interlobular septal thickening
irregular pleural thickening
intralobular reticular opacity
This can progress with increasing reticulation and
traction bronchiectasis and bronchiolectasis
Treatment and prognosis
Antifibrotic medication provides benefit for patients with progressive pulmonary fibrosis 12.