Predisposing factors of Lung abscess-a) Altered sensoriumb) Dental sepsisc) Aggressive treatment of pneumoniad) Subpulmonic effusione) Endobronchial  obstruction
Predisposing factors of lung abscess are :

Aspiration of infective material : Seen in alcoholics, anaesthesia, sinusitis, gingivodental sepsis, coma, gastroesophageal reflux disease.
Antecedent primary bacterial infection : postpneumonic abscess.
Septic embolism : thrombophlebitis, bacterial endocarditis, IV drug abusers.
Neoplasia : causing obstruction to bronchopulmonary segment.
Miscellaenous : Direct spread of infection from suppuration of subphrenic space, pleural cavity, esophagus, spine etc.
When all these causes are excluded, there are still cases in which no reasonable basis for the abscess formation can be identified. These are referred to as primary cryptogenic lung abscesses.
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