Chest Radiograph Patterns in Common Pulmonary Diseases
The chest radiograph remains the first imaging test in lung disease. It does not replace CT or microbiology. Still, pattern recognition guides the next step. Clinicians should read the film with the history in mind.
Consolidation appears as a dense, homogeneous opacity. Air bronchograms often run through it. Lobar pneumonia classically shows this pattern. Pulmonary haemorrhage and some infarcts can look similar. Therefore, fever and sputum still matter.
Atelectasis also creates opacity. Volume loss distinguishes it from consolidation. The fissure moves toward the collapse. The hemidiaphragm may rise. A central tumour or mucus plug often explains lobar collapse.
Interstitial patterns look different. Reticular lines suggest fibrosis, oedema, or lymphangitic spread. Kerley B lines point to interstitial oedema. Honeycombing on a radiograph already implies advanced fibrosis. HRCT then refines the diagnosis.
Nodules and masses need size and number. A solitary nodule raises concern for cancer, tuberculoma, or hamartoma. Multiple nodules may mean metastases, septic emboli, or granulomas. Cavitation inside a nodule suggests TB, abscess, squamous cancer, or fungal disease. Walls and surrounding lung help narrow the list.
Hyperinflation suggests airway obstruction. The diaphragm flattens. The retrosternal space widens. COPD and severe asthma produce this look. Bullae support emphysema. A small, abrupt pneumothorax must not be missed in the same patient.
Pleural disease has clear signs. An effusion blunts the costophrenic angle. A large effusion shifts the mediastinum away. Empyema may look loculated. Pneumothorax shows a visceral pleural line and absent lung markings beyond it. Tension pneumothorax shifts structures to the opposite side and needs urgent action.
Tuberculosis still shows classic clues in endemic regions. Upper-zone fibrocavitary disease suggests post-primary TB. A Ghon focus and calcified nodes suggest old infection. Miliary TB produces countless tiny nodules. These patterns support isolation and laboratory testing.
Pulmonary oedema follows a central pattern.
Bat-wing opacities appear in acute failure. Cardiomegaly and pleural effusions support a cardiac cause. ARDS can look similar but often lacks a large heart. Clinical context separates the two.
Lung cancer has no single face. A persistent mass, collapse, or unilateral hilar enlargement should raise suspicion. A malignant effusion may hide the primary lesion. Comparison with old films is essential.
Good practice is systematic. Check airways, bones, heart, diaphragm, and both lungs. Name the pattern first. Then offer a short differential. The radiograph starts the diagnosis. It does not finish it. Sputum, blood tests, and CT complete the work when the pattern is unclear or the patient is high risk.