An infiltrate of the lower left lobe refers to pulmonary edema, which is the filling of fluid in the lobe or filling by any other substance such as cells (tumors) and inflammatory emissions; whereas an atelectasis of the left lower lobe refers to its collapse, either complete or partial. The visual impression of the atelectasis alone makes it impossible to distinguish from an infiltrate.
Pulmonary infiltrates, such as infections resulting in pneumonia or severe ailments like cystic fibrosis, can cause atelectasis. Other causes of atelectasis may be due to post-surgery complications. In differentiating between a pulmonary infiltrate and atelectasis, the lung volume is measured because its visual density is not enough to distinguish between the two. Patients with an atelectasis will have a loss of lung volume, whereas patients with an infiltrate will have a gain in lung volume.
Symptoms of an atelectasis include chest pain, difficulty breathing and coughing. Common treatments for atelectasis are all aimed to re-inflate the lung. These treatments may include a range of breathing exercises or removal of any blockage such as mucus plugs or tumors. Symptoms of pulmonary infiltration depend on the cause but can include chest pain, shortness of breath and fever, such as with pneumonia. Treatment for infiltration also depends on the cause of the infiltration.