Lung abscesses. Coloured computed tomography (CT) scan through a patient's chest. The front of the body is at top. A large abscess (black) is seen in the right lung (left) and a small abscess in the left lung (right). The lungs (dark red) are either side of the heart (orange, centre). The main body artery (red) and vein (blue) are between the heart and spine (white). Branching airways and blood vessels are seen in the lungs. An abscess is a collection of pus surrounded by inflamed tissue. It is usually due to a bacterial infection and is treated by surgical draining of the pus and drugs to treat the infection. Such abscesses are rare in healthy people, mostly affecting the old or weak.