[3] The invading organism starts multiplying, thereby releasing toxins that cause inflammation and edema of the lung parenchyma.

This leads to consolidation or solidification, terms used for macroscopic or radiologic appearance of the lungs affected by pneumonia.

Bacterial pneumonia is mainly classified into lobar and diffuse depending on the degree of lung irritation or damage.

Classically, the disease has four stages:[1] The openings between the alveoli known as the pores of Kohn, and the collateral airways of the canals of Lambert, are undeveloped in children.

Pathological specimens to be obtained for investigations include: On a posteroanterior and lateral chest radiograph, an entire lobe will be radiopaque, which is indicative of lobar pneumonia.