Blocked abscess was visualized as roundish neoplasm with hypechromogenic liquid content in which we detected isochromogenic suspensions (4-5 points at Fleindler’s scale), loosely distributed throughout a cavity of destruction (suppurative detritus), without achromogenic signals of air. At acute course a capsule of an abscess was not visualized. Purulent cavity was limited by lung parenchyma itself, which along with preserved air content was of the form of hypochromogenic line (2-3 points at Fleindler’s scale), but when air content was lost because of pneumonic infiltration, it was visualized as moderately chromogenic tissue (3-4 points). A width of this line varied depending on clarity of abscess limiting and significance of perifocal changes in a lung.

Burst of purulent content into bronchi meant start of open stage of abscess development with heterogeneous structure due to appearance of achromogenic signals against the background of hyperchromogenic fluid with suspensions. The efficiency of spontaneous drainage was evaluated by a quantity and a character of achromogenic inclusions (air) distribution in a purulent exudate. The drainage was considered insufficient at single or multiple lesser achromogenic cavities, diffusely distributed throughout the whole cavity of an abscess against the background of significantly prevailing hyperchromogenic content.