肺上叶白色箭头所指脓肿。脓肿的液化性坏死物排出后留下空洞。胸部X线显示：脓肿中央显示气液平面。
The white arrows mark areas of abscess formation in the upper lobe of this lung. The liquefactive necrosis of an abscess is apparent, because the purulent contents are draining out to leave a cavity. On a chest radiograph, the liquefied central contents of an abscess can appear as an "air-fluid level".