What it is

• Pneumonia means infection/inflammation of lung parenchyma (especially alveoli).
• In lobar pneumonia, consolidation is confluent and lobar rather than patchy.
• Classically associated with bacterial infection, especially Streptococcus pneumoniae (also possible with Klebsiella and others).
  (Fishman’s Pulmonary Diseases and Disorders, p. 1640; Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 662)

How it develops (pathology)

1. Congestion: heavy, red, boggy lung; vascular engorgement and edema fluid in alveoli
2. Red hepatization: alveoli fill with neutrophils, RBCs, fibrin; firm “liver-like” lobe
3. Gray hepatization: RBC breakdown with persistent fibrinopurulent exudate; gray-brown appearance
4. Resolution: enzymatic digestion and clearance of exudate by macrophages/resorption/expectoration, or organization
   (Robbins & Kumar Basic Pathology, p. 470; Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 662)

Symptoms and signs

• Fever, chills/rigors
• Cough with sputum (sometimes rust-colored or purulent)
• Dyspnea
• Pleuritic chest pain
• Exam findings of consolidation (bronchial breath sounds, crackles)
  (Tintinalli’s Emergency Medicine, p. 505; Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 662)

Imaging features

• Lobar air-space consolidation on chest imaging
• Air bronchograms are a classic clue (air-filled bronchi outlined by surrounding alveolar opacification)
• Pleural effusion may accompany severe bacterial cases
  (Fishman’s Pulmonary Diseases and Disorders, p. 1640)

Complications

• Lung tissue necrosis/abscess
• Parapneumonic effusion or empyema
• Pleuritis with adhesions
• Bacteremic spread causing meningitis, endocarditis, pericarditis, septic arthritis, etc.
  (Robbins & Kumar Basic Pathology, p. 470; Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 662)

Clinical diagnosis and treatment principles

• Diagnosis is clinical plus radiographic infiltrate (history/exam + chest imaging).
• Identify severe disease and need for hospitalization.
• Start empiric antibiotics targeting common CAP pathogens, then narrow if microbiology identifies an organism.
• Supportive care: oxygen (if hypoxemic), fluids, antipyretics, monitoring for complications.
  (Tintinalli’s Emergency Medicine, p. 505)

Lobar vs bronchopneumonia (quick distinction)

• Lobar pneumonia: confluent involvement of large part/all of a lobe
• Bronchopneumonia: patchy, often multilobar/basal foci centered around bronchi/bronchioles