<unk>  may be classified according to the etiology, anatomical location, and pathological course of the disease. Primary thoracic<unk>  occurs most commonly as iatrogenic<unk>  without associated pneumonia whereas secondary<unk>  happens more commonly secondary to pneumonia.<unk>  necessitans is a spontaneous  discharge of an<unk>  that has burrowed through the parietal pleura into the chest wall to form a subcutaneous abscess that may eventually rupture through the skin.  On the basis of anatomical location,<unk>  may be classified depending on the affected organ for example; gallbladder<unk> , subdural<unk> , joint<unk>  and<unk>  cystitis.<unk>  is mostly caused by bacteria. It may be tuberculous or nontuberculous. Tuberculous<unk>  is the most common cause of<unk>  necessitans with majority of affected patients being immunocompromised. There are 3 stages of<unk>  which are important in terms of the laboratory findings. These are exudative, fibrinopurulent and organizing.
Empyema classification
Emphysema classification
Atelectasis classification
Silicosis classification
Bronchiectasis classification
Pneumoconiosis classification
Hemoptysis classification
Pulmonary embolism classification