Pulmonary consolidation is a term denoting the filling of alveoli and the respiratory bronchioles with dense material, such as fluid, pus, blood or cellular content. As a result, infections, particularly pneumonia, as well as malignancies, immune-mediated reactions, and various other etiologies can cause pulmonary consolidation that is visible on X-rays and other imaging studies. Computed tomography and magnetic resonance imaging are often employed to confirm the underlying cause.
Pulmonary consolidation is a pathological process during which infiltration of alveoli by a range of dense materials (pus, blood, fluid or cells) causes an improper function of the affected area. One of the most important etiologies is pneumonia (of any type), when inflammatory cells, pus and sometimes even blood obstruct the air flow through the respiratory system and the alveoli, resulting in the inability for gas-exchange processes to occur. On the other hand, pulmonary edema, often seen in congestive heart failure, is the principal event that leads to fluid-filled air spaces. Other notable causes include malignant diseases (both primary and metastatic tumors of the lungs), hypersensitivity or aspirational pneumonitis, occupational lung disorders (such as silicosis), cystic fibrosis, and pulmonary embolism with subsequent infarction   . Regardless of the underlying etiology, symptoms include dyspnea, increased respiratory effort and a cough (often productive), whereas fever (in the setting of an infection) or hemoptysis (primarily seen in tumors) are infrequently present  . Symptoms may gradually appear when chronic conditions are responsible for pulmonary consolidation, but they can also develop abruptly and cause a significant risk for the patient's life, as severe respiratory insufficiency is a known complication if a large portion of the lung is affected by this pathological process.
Pulmonary consolidation is a radiological sign that is identified using different imaging studies, but initial signs of an ongoing process in the lungs can also be observed during a physical examination. The intensity of vibration of the chest wall while a patient is speaking (known as tactile fremitus) will be increased in areas of consolidation, while percussion of the intercostal spaces can reveal dullness, similarly to percussing of a solid organ  . In addition, abnormal transmission of voice during auscultation (bronchophony) may be noted . Clinical suspicion toward a respiratory pathology should be raised if any of the mentioned clinical signs (in addition to abnormal lung sounds) are present, in which case imaging studies should be performed as soon as possible, especially if patient rapidly deteriorates. Plain radiography is a useful initial method . Lung ultrasonography has recently shown to be a reliable method for detection of consolidations  , while computed tomography (CT) is the gold standard in visualizing many respiratory disorders and is performed whenever possible . Magnetic resonance imaging (MRI) has also been mentioned as a good method for visualization of pulmonary consolidation .