7. Pneumonia.pdf

Pneumonia AP DR. MIE MIE SEIN MBBS BLOCK 2  Learning Outcomes 1. Classify pneumonia. (C2) 2. Describe the pathogenesis and morphology of lobar pneumonia. (C2) 3. Describe the pathogenesis and morphology of bronchopneumonia. (C2) 4. St...

Pneumonia AP DR. MIE MIE SEIN MBBS BLOCK 2  Learning Outcomes 1. Classify pneumonia. (C2) 2. Describe the pathogenesis and morphology of lobar pneumonia. (C2) 3. Describe the pathogenesis and morphology of bronchopneumonia. (C2) 4. State the atypical pneumonia and non-infective pneumonia. (C1) 5. Compare the clinicopathological features between lobar pneumonia and bronchopneumonia. (C4) Manipal University College Malaysia 2  Definition Pneumonia is defined as collection of inflammatory exudate in lung parenchyma distal to terminal bronchioles. Mostly resulting in consolidation (solidification) of lung part(s). Manipal University College Malaysia 3  Classifications of pneumonia Criterion Type Example/comment Anatomical pattern Bronchopneumonia Most widely used classification before identifying aetiological agent Lobar pneumonia Clinical Primary In an otherwise healthy person circumstances Secondary With local or systemic defects in defence Aetiological agents Bacterial Streptococcus pneumoniae Staphylococcus aureus Mycobacterium tuberculosis, etc. Viral Influenza, measles, etc. Fungal Cryptococcus, Candida, Aspergillus, etc. Other Pneumocystis jiroveci, Mycoplasma, Aspiration, lipid, eosinophilic Host reaction Fibrinous According to dominant component of exudate Suppurative Manipal University College Malaysia 4  Pathogenesis Pneumonia usually occurs whenever defense mechanisms of respiratory system are impaired or immunity of the host is low. The pulmonary defense mechanisms may also be compromised by many factors, including: Loss or suppression of the cough reflex, as a result of altered sensorium (e.g., coma), anesthesia, neuromuscular disorders, drugs, or chest pain, any of which may lead to aspiration of gastric contents. Dysfunction of the mucociliary apparatus, which can be caused by cigarette smoke, inhalation of hot or corrosive gases, viral diseases, Accumulation of secretions in conditions such as cystic fibrosis and bronchial obstruction. Interference with the phagocytic and bactericidal activities of alveolar macrophages by alcohol, tobacco smoke, anoxia, or oxygen intoxication. Pulmonary congestion and edema. Manipal University College Malaysia 5  Lobar pneumonia Affects anatomically delineated segment(s) or the entirety, of a lobe or lung Relatively uncommon in infancy and old age Affects males more than females 90% due to Streptococcus pneumoniae (pneumococcus) Pneumococcal pneumonia typically affects otherwise healthy adults between 20 and 50 years of age Lobar pneumonia caused by Klebsiella typically affects the elderly, diabetics or alcoholics. Manipal University College Malaysia 6  Clinical features Symptoms Cough, fever and production of sputum. The sputum appears purulent and may contain flecks of blood, so-called ‘rusty’ sputum. Occasional patients may have hemoptysis. Fever can be very high (over 40°C), with rigors. (Shaking chills) Acute pleuritic chest pain on deep inspiration reflects inflammation of the pleura (pleurisy). Signs As the lung becomes consolidated, the chest signs are dullness to percussion with bronchial breathing. Pleural friction rub Manipal University College Malaysia 7  Morphological changes in Lobar Pneumonia Congestion. This first stage lasts for about 24 hours and represents the outpouring of a protein-rich exudate into alveolar spaces, with venous congestion. The lung is heavy, oedematous and red. Red hepatisation. In this second stage, which lasts for a few days, there is massive accumulation in the alveolar spaces of polymorphs, together with some lymphocytes and macrophages. Many red cells are also extravasated from the distended capillaries. The overlying pleura bears a fibrinous exudate. The lung is red, solid and airless, with a consistency resembling fresh liver. Manipal University College Malaysia 8  Grey hepatisation. This third stage also lasts a few days and represents further accumulation of fibrin, with destruction of white cells and red cells. The lung is now grey–brown and solid. Resolution. This fourth stage occurs at about 8–10 days in untreated cases, and represents the resorption of exudate and enzymatic digestion of inflammatory debris, with preservation of the underlying alveolar wall architecture. Most cases of acute lobar pneumonia resolve in this way but infections with some more virulent bacteria may lead to tissue damage and fibrosis or abscess formation (e.g. Staphylococcus aureus, Klebsiella pneumoniae). Manipal University College Malaysia 9  Stages of pneumonia (A) Acute pneumonia The congested septal capillaries and numerous intra-alveolar neutrophils are characteristic of A early red hepatization. Fibrin nets have not yet formed. (B) Early organization of intra-alveolar exudate, seen focally to be streaming through B the pores of Kohn (arrow). (C) Advanced organizing pneumonia The exudates have been converted to fibromyxoid masses rich in macrophages and C fibroblasts. Source: Robbins and cotran Pathologic basis of disease Manipal University College Malaysia 10  Lobar pneumonia gray hepatization lower lobe is uniformly consolidated Source: Robbins and cotran Pathologic basis of disease Manipal University College Malaysia 11  Chest X ray chest radiograph shows dense right upper lobe air-space opacity, which bows the right minor fissure inferiorly (arrows) Source: https://www.pathologyoutlines.com/ Manipal University College Malaysia 12  Bronchopneumonia Bronchopneumonia has a characteristic patchy distribution, centred on inflamed bronchioles and bronchi with subsequent spread to surrounding alveoli. Often several lobes or bilateral It occurs most commonly in old age, in infancy and in patients with debilitating diseases, such as cancer, cardiac failure, chronic renal failure or cerebrovascular accidents. Typical organisms include staphylococci, streptococci and Haemophilus influenzae. Manipal University College Malaysia 13  Bronchopneumonia patches of consolidation (arrows) Source: Robbins and cotran Pathologic basis of disease Manipal University College Malaysia 14  Chest X ray chest radiograph shows patchy bronchovascular thickening (arrows) in the left lower lobe; trace blunting of the left costophrenic angle is present Source: https://www.pathologyoutlines.com/ Manipal University College Malaysia 15  Complications of Pneumonia Abscess formation: results from tissue destruction ( more in case of Klebsiella or type III Pneumococcal infections) Empyema: Virulent bacterial strains induce suppuration in the pleural cavity causing the intra-pleural fibrosuppurative reaction Fibrosis: Organization of intra-alveolar exudate may convert affected lung into solid fibrous tissue Bacterial dissemination: Dissemination of bacteria may lead to endocarditis, pericarditis, meningitis, suppurative arthritis and formation of metastatic abscesses in various organs, e.g, kidneys, spleen, etc. Manipal University College Malaysia 16  Atypical Pneumonia Pneumonias caused by organisms other than traditional bacteria are often referred to as ‘atypical pneumonias’. It is defined as an acute febrile respiratory disease which manifests with patchy inflammatory changes confined to alveolar space and pulmonary interstitium, Causative organisms are: Mycoplasma pneumoniae Influenza virus type A and B Respiratory syncytial viruses, adenovirus, rhinovirus, rubeola and varicella virus Chlamydia Coxiella burnetii Manipal University College Malaysia 17  Non-Infective Pneumonias Cryptogenic organising pneumonia Aspiration pneumonia when fluid or food is aspirated into the lung Lipid pneumonia endogenous: associated with airway obstruction causing distal collections of foamy macrophages and giant cells. This is often seen distal to bronchial carcinoma or an inhaled foreign body. exogenous: due to aspiration of material containing a high concentration of lipid. (liquid paraffin or oily nose drops) Manipal University College Malaysia 18  Differences between bronchopneumonia and lobar pneumonia Features Bronchopneumonia Lobar pneumonia Definition Patchy consolidation of multiple lobes (Bilateral) Involvement of a large part of a lobe or entire lobe, diffuse consolidation Predisposing illness Bronchitis/Bronchiolitis, chronic debility Affects healthy individuals Immune status Usually affects immunosuppressed individuals Affects previously healthy individuals Distribution Basal area more affected as secretions gravitate into May involve any lobe lower lobe Stages of inflammation No clear-cut division Divided into four stages Organisms Staphylococci, Streptococci, Pneumococci, Pneumococci/Streptococcus pneumoniae (95%) H. influenzae, Pseudomonas aeruginosa, Coliforms Klebsiella, H.influenzae Severity Less More Sputum Purulent, non-haemorrhagic Initially scanty, watery; later thick, purulent, Manipal University College Malaysia haemorrhagic 19  Distribution of lesions in bronchopneumonia and lobar pneumonia. [A] Bronchopneumonia is characterised by focal inflammation centred on the airways; it is often bilateral. [B] Lobar pneumonia is characterised by diffuse inflammation affecting the entire lobe. Pleural exudate is common. Source: Underwood’s Pathology Manipal University College Malaysia 20  TAKE HOME MESSAGE Pneumonia is defined as collection of inflammatory exudate in lung parenchyma distal to terminal bronchioles. S. pneumoniae (the pneumococcus) is the most common cause of acute pneumonia; the distribution of inflammation is usually lobar. Lobar pneumonias evolve through four stages: congestion, red hepatization, gray hepatization, and resolution. Important causes of viral pneumonia include influenza virus, and coronavirus COVID-19, the latter a newly emergent pathogen. Bacterial pneumonias are characterized by predominantly intra-alveolar neutrophilic inflammation, while viral pneumonia shows interstitial lymphocytic inflammation Manipal University College Malaysia 21 References: Robbins and Cotran Pathologic Basis of Disease 10th Edition Underwood’s pathology: A clinical approach 7th edition Manipal University College Malaysia 22  Thank you! Manipal University College Malaysia 23