PNEUMONIA .pptx

lung

1. PNEUMONIA DR.MANJULA N MBBS MD (PATHOLOGY)

2. INTRODUCTION Pneumonia is defined as infection of the lung parenchyma . It causes the alveoli to be filled with inflammatory exudates and usually results in consolidation (solidification) of lung.

3. Pneumonia is defined as acute inflammation of the lung parenchyma distal to the terminal bronchioles (consisting of the respiratory bronchiole, alveolar ducts, alveolar sacs and alveoli). The terms ‘ pneumonia ’ and ‘ pneumonitis ’ are often used synonymously for inflammation of the lungs, while ‘ consolidation ’ (meaning solidification) is the term used for gross and radiologic appearance of the lungs in pneumonia.

4. PATHOGENESIS The microorganisms gain entry into the lungs by one of the following four routes: 1. Inhalation of the microbes present in the air. 2. Aspiration of organisms from the nasopharynx or oropharynx. 3. Haematogenous spread from a distant focus of infection. 4. Direct spread from an adjoining site of infection.

5. RISK FACTORS Immunological deficiency. Treatment with immunosuppressive agents. Leukopenia. Impaired local defense mechanisms.

6. RISK FACTORS Loss or suppression of the cough reflex, e.g., coma, anesthesia, or neuromuscular disorders. Damage or injury to the mucociliary apparatus: e.g , cigarette smoke, viral diseases. Accumulation of secretions: Cystic fibrosis .

7. CLASSIFICATION OF PNEUMONIA Classification depending on the anatomic distribution: Lobar pneumonia Bronchopneumonia Interstitial pneumonia

8. CLASSIFICATION OF PNEUMONIA Etiological classification: Primary Secondary Suppurative

9. CLASSIFICATION OF PNEUMONIA Clinical setting in which the infection occurs: Community-acquired acute pneumonia Community-acquired atypical pneumonia Nosocomial pneumonia or hospital-acquired pneumonia Pneumonia in immunocompromised host Healthcare associated pneumonia

10. COMMUNITY-ACQUIRED PNEUMONIA Causative Microorganisms : these may be bacteria or virus. Bacterial infection of the lung parenchyma causes the alveoli to be filled with an inflammatory exudate and produces consolidation (solidification) of the pulmonary parenchyma. Pathogenesis: v arious mechanisms by which lung is infected are as follows:- Aspiration of oropharyngeal contents: Most frequent . Inhalation of aerosolized droplets: Second most frequent. Bloodstream infection: Less common. MCC – CAP - Streptococcus pneumoniae. Infectious pneumonia in patients living independently in the community.

11. BACTERIAL PNEUMONIA Depending on the anatomic distribution, bacterial pneumonia can be divided into: Lobular bronchopneumonia and Lobar pneumonia. Lobar pneumonia : It is defined as fibrinosuppurative consolidation of a large portion of a lobe or of an entire lobe of the lung. Bronchopneumonia: It is characterized by patchy (scattered solid foci) area consolidation in the same or several lobes of the lung.

12. LOBAR PNEUMONIA Laennec’s description divides lobar pneumonia into 4 sequential pathologic phases:- MORPHOLOGICAL STAGES The inflammatory response is classically divided into four stages:- Congestion, Red hepatization, Gray hepatization and Resolution Characterized by diffuse inflammation affecting part or entire lobe, usually the lower lobes.

13. BRONCHOPNEUMONIA Gross: Bronchopneumonia is characterized by widespread focal/patchy areas of acute suppurative inflammation. They are centered on bronchioles and bronchi with subsequent spread to surrounding alveoli. The involved alveoli show consolidation. The consolidated areas are larger and more numerous in lower lobes (because of the tendency of secretions to gravitate into the lower lobes) and frequently bilateral. Cut section : It appears slightly raised above the surface of the surrounding lung and measures several millimeters in diameter. They are dry, solid, granular, gray-red to yellow, and poorly delimited at their margins. Microscopy : The bronchi, bronchioles and adjacent alveolar spaces are filled with exudate rich in neutrophils.

14. STAGE OF CONGESTION This stage lasts for less than 24 hours. Gross : The involved lobe of the lung is heavy, boggy and red. A blood-stained frothy fluid oozes from the cut surface. Microscopy : Dilatation and congestion of capillaries in the alveolar walls. The air spaces in the alveoli are filled with pale eosinophilic fluid with few neutrophils, red cells and numerous bacteria.

15. STAGE OF RED HEPATIZATION It lasts for 2–3 days. Gross : The lobe appears distinctly red, firm and airless. The firm consistency of the affected lobe resembles that of the liver, hence termed red hepatization. The pleura may show serofibrinous pleurisy. Cut section: shows red and granular appearance. Microscopy : Alveoli show exudate and interlacing strands of fibrin. Numerous neutrophils and red cells are found in the fibrin meshwork.

16. STAGE OF GRAY HEPATIZATION Gray hepatization of lungs is seen on 5–7 days. Gross : The affected lobe gradually loses its red color and assumes gray appearance. Cut surface shows gray, dry and granular appearance. Microscopy : Progressive disintegration of red cells. Fibrinosuppurative exudate in the alveoli in which neutrophils are replaced by macrophages. There is a clear space between the alveolar wall and the exudate due to contraction of the fibrin thread present in the exudate.

17. STAGE OF RESOLUTION Resolution occurs by liquefaction of the previously solid, fibrinous constituents of the exudate in the air spaces. The fibrinous exudate within the air spaces undergoes progressive liquefaction to produce granular and semifluid debris. The liquefaction is due to fibrinolytic enzymes liberated from neutrophils. The liquefied material is removed, partly by expectoration, but mainly ingested by macrophages and drained through lymphatics. If not removed, it may become organized by ingrowth of capillaries and fibroblasts into the exudate. Gross : The affected lobe becomes more crepitant as the air spaces reopen. Cut section appears frothy . Microscopy : The alveolar space shows granular material and semifluid debris.

18. Hospital-acquired pneumonias Predisposing factors:- Severe underlying disease, Immunosuppression, Prolonged antibiotic therapy, Patients on mechanical ventilation or invasive access devices, such as intravascular catheters. The hospital-acquired pneumonias are serious and may be life-threatening. MCC – HAP – Gram negative bacterias – Klebsiela , Pseudomonas. Pulmonary infections acquired in the course of a hospital stay.

19. Etiological types of HIV infection associated pneumoniae Pneumocystis jirovecii Cytomegalovirus Mycobacterium avium- intracellulare Mycobacterium tuberculosis Streptococcus pneumoniae Haemophilus influenzae Invasive aspergillosis Invasive candidiasis

20. COMPLICATIONS Lung abscess : It may develop with extensive tissue destruction and necrosis. Organization : Delayed and incomplete resolution can cause ingrowth of granulation tissue into the alveolar exudate. Spread of infection to the pleural cavity: It may result in Pleuritis. Pleural effusion Pyothorax Empyema: Bacteremia

21. NON INFECTIVE PNEUMONIAS Some other types of pneumonias caused by certain noninfective varieties (e.g. aspiration pneumonia, hypostatic pneumonia and lipid pneumonia)

22. Aspiration or inhalation pneumonia It results from inhalation of different agents into the lungs. These substances include food, gastric contents, foreign body and infected material from oral cavity. A number of factors predispose to inhalation pneumonia which include:- Unconsciousness, Drunkenness, Neurological disorders affecting swallowing, Drowning, In premature infants and congenital tracheo -oesophageal fistula.

23. MORPHOLOGIC FEATURES Pathologic changes vary depending upon the aspirated particulate matter but in general right lung is affected more often due to direct path from the main bronchus. 1. Aspiration of small amount of sterile foreign matter such as acidic gastric contents produces chemical pneumonitis. It is characterised by haemorrhagic pulmonary oedema with presence of particles in the bronchioles. 2. Non-sterile aspirate causes widespread bronchopneumonia with multiple areas of necrosis and suppuration. A granulomatous reaction with foreign body giant cells may surround the aspirated vegetable matter.

24. SUMMARY Lobar pneumonia : Most common cause is Streptococcus pneumoniae or Pneumococcus Lobar pneumonia: Four stages 1. Congestion 2. Red hepatization 3. Gray hepatization 4. Resolution Bronchopneumonia : Acute bronchitis with extension into adjacent alveoli. Bronchopneumonia: Usually • Bilateral basal location due to gravitation of secretions • Affects extremes of age (infants or old) • X-ray chest—patchy opacification of the lobe Complications of pneumonia : • Lung abscess • Organization • Spread of infection to the pleura • Bacteremic dissemination X-ray chest: Gold standard for diagnosing pneumonia. Positive Gram stain on sputum : More useful than culture

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