Fig. 3.1 Lobar pneumonia in a 74-year-old man with acute myeloid leukemia and neutropenic fever. Urine culture disclosed gram-positive cocci. (a, b) Thin-section (2.5-mm section thickness) CT scans at levels of the right upper (a) and middle lobar (b) bronchi, respectively, show lobar parenchymal opacity involving the right upper and middle lobes.

(c, d) Coronal reformatted images at levels showing the right upper lobar bronchus (RUB) (c) and right middle lobar bronchus (RMB) (d), respectively, demonstrate parenchymal opacity in the right upper and middle lobes. Also note crazy-paving appearance (arrows in c) within parenchymal opacity lesion

Lobar Pneumonia

Pathology and Pathogenesis

Fibrinosuppurative consolidation of a large portion of a lobe, or of entire lobe, is the dominant characteristic of lobar pneumonia, while patchy consolidation deÞnes bronchopneumonia. There are four stages of the inßammatory response: congestion (vascular engorgement, intra-alveolar ßuid with few neutrophils), red hepatization (massive conßuent exudation with neutrophils and red blood cells, Þlling alveolar spaces), gray hepatization (progressive disintegration of red

blood cells), and resolution (organized by Þbroblasts growing into it) [11].

Symptoms and Signs

Acute development of fever and purulent sputum is the classic manifestation of lobar pneumonia. Dyspnea, pleuritic chest pain, and hemoptysis may be present. Leukocytosis is often found, suggesting acute inßammatory process. In older debilitated or immunosuppressed patients, it may be mild or absent. Inspiratory crackle is heard on chest auscultation.