What is the basic radiographic sign of left lower lobe pneumonia on chest X-ray?

• A. Patchy or focal airspace consolidation in the left lower lobe consistent with pneumonia.
• B. Diffuse interstitial markings throughout both lungs.
• C. Cardiomegaly with edema.
• D. Atelectasis of the right middle lobe.

Answer: (A)

Pneumonia shows as air-space consolidation where the alveoli are filled with inflammatory debris and fluid, increasing density on chest X-ray. When the infection is in the left lower lobe, you see a patchy or focal opacity in that left basal region. This localized density reflects the lobar or segmental pneumonia pattern typical for bacterial infection in a specific lobe and may show air bronchograms if airway air becomes visible against the dense alveolar material. The other patterns—diffuse interstitial markings (suggesting edema or interstitial processes), cardiomegaly with edema (heart failure), or right middle lobe atelectasis (volume loss on the wrong side)—do not match the classic left lower lobe focal consolidation, making the described left lower lobe patchy consolidation the best sign of the finding.