On chest radiographs, how do viral and bacterial pneumonia typically differ in children?

• A. Viral: focal consolidation; Bacterial: diffuse interstitial markings
• B. Viral: lobar consolidation; Bacterial: diffuse interstitial markings
• C. Viral: diffuse interstitial markings; Bacterial: focal consolidation
• D. Viral: diffuse interstitial markings; Bacterial: pleural effusion

Answer: (C)

In children, the chest radiograph patterns help distinguish viral from bacterial pneumonia. Viral infections commonly produce diffuse interstitial markings, reflecting inflammation around the airways (bronchiolitis and peribronchial thickening) and often accompanying hyperinflation. Bacterial pneumonia, on the other hand, tends to cause focal air-space (alveolar) consolidation in one or a few lobes, representing localized filling of the alveoli with exudate.

So the best description is: viral pneumonia shows diffuse interstitial markings, while bacterial pneumonia shows focal consolidation. While pleural effusion can occur with bacterial infections, it’s not the defining pattern and is less reliable for differentiation.