Internal medicine

Empyema necessitatis
the spontaneous extension of pus through the
parietal pleura and chest wall from an empyema with
the formation of a subcutaneous abscess. In most
circumstances this occurs secondary to a tuberculous
empyema. There may be an associated bronchopleural
fistula. CT is used to demonstrate the empyema and
its extension through the chest wall and associated
bronchopleural fistula.