Mediastinal shift toward the atelectatic lung occurs in which atelectasis?

• A. Atelectasis
• B. Resorption atelectasis
• C. Contraction atelectasis
• D. Pulmonary edema

Answer: (B)

When a bronchus is blocked, air distal to the blockage is absorbed and the distal alveoli collapse, causing loss of volume on that side—the process called resorption (obstructive) atelectasis. That reduction in lung volume tugs the mediastinal structures toward the collapsed lung, producing a mediastinal shift toward the atelectatic side. Pulmonary edema isn’t an atelectasis process and doesn’t create this specific shift pattern. External compression (not listed) would typically push the mediastinum away from the affected side, and contraction atelectasis involves fibrotic shrinking of the lung with its own, less typical, shifting behavior.