Lobular pneumonia is an acute purulent inflammatory disease caused mainly by purulent bacteria, with the lobules of the lung as the lesion unit. The lesions are often centered on the small bronchi, so it is also called bronchopneumonia, which occurs mainly in children, frail elderly and bedridden people. Most lobar pneumonia is caused by bacteria. The common causative agents are Staphylococcus, Pneumococcus, Haemophilus, Klebsiella, Streptococcus, Pseudomonas aeruginosa and Escherichia coli. The onset of lobar pneumonia is often associated with the less pathogenic groups of the above bacteria, which are usually resident in the oral cavity or upper respiratory tract, with the less pathogenic pneumococci types 4, 6, and 10 being the most common causative organisms. When suffering from infectious diseases or malnutrition, cachexia, coma, anesthesia and post-surgery, these bacteria may invade the normally sterile fine bronchi and terminal lung tissue to grow and multiply, causing lobar pneumonia due to decreased body resistance and impaired respiratory system defenses. Therefore, lobar pneumonia is often a complication of certain diseases, such as post-measles pneumonia, post-surgical pneumonia, aspiration pneumonia, and crushing pneumonia. Pathological changes The lesion of lobar pneumonia is characterized by purulent inflammation of the lung tissue centered on the fine bronchi. To the naked eye, solid grayish-yellow lesions are scattered on the surface and in sections of both lungs, mostly in the lower lobes and dorsal aspect. The lesions vary in size and are mostly about 0.5-1 cm in diameter (equivalent to the lung lobules) and irregular in shape, and a cross-section of the lesion’s fine bronchial hair is often visible in the center of the lesion. In severe cases, the lesions may fuse with each other to form a patch, or even involve the entire lobe and develop into fused bronchitis, usually without accumulating pleura.