0908 - Pathology of Pneumonia Flashcards
What are the layers of airway tissue?
Lumen, mucose, submucosia, fibrocartilage, adventitia
What type of inflammation is typically seen in bacterial or fungal pneumonia?
Acute inflammation characterised by neutrophils and exudate.
What type of inflammation is typically seen in viral pneumonia?
Chronic inflammation, characterised by mononuclear cells (agranular - lymphocytes, plasma cells). Inflammation is predominantly in the alveolar wall/interstitium, but some oedema fluid enters the alveolus.
How can pneumonia be classified?
By causative agent, clinical setting, mechanism (e.g. aspiration), or anatomic distribution - bronchogenic or lobar.
What factors influence the pathogenesis of pneumonia?
Virulence of the organism
Factors affecting host resistance - chronic disease, immune deficiency, or extremes of age.
Factors affecting airway defences - altered cough reflex, ineffective mucociliary escalator, interference with macrophage activity, accumulation of secretions in the airways.
What are the signs and symptoms of bacterial pneumonia?
Fever Leukocytosis (acute inflammation) Cough with sputum (alveolar exudate) Pleuritic chest pain (pleuritis) increased RR Cyanosis (V/Q mismatch)
What are the four classic stages of bacterial lobar pneumonia?
Congestion - leaking of oedema fluid into lung
Red Hepatisation - Neutrophils and exudate, fibrinogen converted to fibrin, RBCs present
Grey Hepatisation - Decreased vascular response, but still ‘solid’ because of exudate
Resolution - No more exudate - all coughed up/digested.
No longer as applicable due to antibiotics.
What signs indicate the congestive stage of bacterial pneumonia?
Heavy, enlarged lobe, with dilated and congested capillaries. Air spaces filled with pale fluid and scattered blood cells - bacteria only occasional.
What signs indicate the red hepatic stage of bacterial pneumonia?
Cut surface is dry and red - ‘solid’ and like liver. Increased numbers of neutrophils, with clotted oedematous fluid in alveolar spaces and more numerous bacteria.
What signs indicate the grey hepatisation stage of bacterial pneumonia?
Loss of red colour after 2-3 days, spreads from hilum out. Large numbers of neutrophils, less capillary congestion, and decreased blood flow through unventilated lobe.
What signs indicate the resolution stage of bacterial pneumonia?
Liquefaction of previously solid exudate, fibrinolytic enzymes, apoptosis of neutraphils, and fluid contents removed through expectoration (coughing) or lymphatics. Takes several weeks.
What are the cardinal signs of viral pneumonia?
Rarely fatal without superimposed bacterial infection. Infalmmation is interstitial and lymphocytic. Lots of lymphocytes in the wall - widening of interstitium.
What categorises respiratory syncytial virus pneumonia?
Winter epidemics, children LRT, bronchiolitis and pneumonia, destruction of bronchiolar epithelium with debris, mucus plugs and fibrin. Giant cells (macrophages) and lymphocytes.
What categorises fungal infections of the lung?
Can be pathogenic or opportunistic. Often form abscesses.
What categorises Pneumocystis pneumonia?
Opportunistic fungus, causes pneumonia in AIDS patients and malnourished children. Breathlessless, fever and cough. Macro - airless, red, beefy lungs. Micro, alveolar spaces filled with foamy, amorphous material, mild interstitial infiltrate, silver stain reveals numerous small round cysts.
