By definition, subsegmental atelectasis (regardless of its etiology) does not produce volume loss and subsequent shifting of mobile thoracic structures, and in most cases lacks clinical relevance and does not need to be reported.

Should I worry about atelectasis?

In an adult, atelectasis in a small area of the lung is usually not life threatening. The rest of the lung can make up for the collapsed area, bringing in enough oxygen for the body to function.

What causes Subsegmental atelectasis?

Also called discoid or subsegmental atelectasis, this type is seen most commonly on chest radiographs. Platelike atelectasis probably occurs because of obstruction of a small bronchus and is observed in states of hypoventilation, pulmonary embolism, or lower respiratory tract infection.