PNEUMONIA & SUPPURATIVE LUNG DISEASES

Dr. Thin Thin Win @ SafiyaDepartment of Pathology, PPSP

PNEUMONIA

Definition

Infection of the lung parenchyma(consolidation or hardening of lung parenchyma)

Etiology

Result whenever pulmonary defense mechanism are impaired or resistance of host is loweredPulmonary defense mechanism –1. cough reflex2. mucociliary apparatus3. phagocytic alveolar macrophages

Etiology

Caused by varieties of infectious agent such as bacteria, viruses, fungi, mycoplasma etc:…Mostly bacterial pneumonia -Pneumococci, Klebsiella pneumoniae, Staphylococci, Streptococci, H.influenzae, Pseudomonas aeruginosa

Clearing mechanism can be interfered with many factors:

1. Loss or suppression of cough reflex -aspiration of gastric contents in coma, anesthesia, neuromuscular disorders, drugs, chest pain –aspiration pneumonia

2. Injury to mucociliary apparatus –cigarette smoking, inhalation of hot or corrosive gases, viral d/s, genetic disorders

Clearing mechanism can be interfered with many factors:

3. Interfered phagocytic/ bactericidal action of alveolar macrophages –alcohol, smoking, anoxia, O2 intoxication

4. Pulmonary congestion & edema5. Accumulation of secretions – cystic

fibrosis & bronchial obstruction

Bacterial Pneumonia(community acquired acute pneumonia)

2 gross patterns

Lobar pneumoniaLobular bronchopneumonia

Lobar pneumonia

Consolidation of a large portion of a lobe or an entire lobe (whereas patchy consolidation in bronchopneumonia)

Lobar pneumonia Bronchopneumonia

A closer view of the lobar pneumonia demonstrates the distinct difference between the upper lobe and the consolidated lower lobe.

Uniformly consolidated lower lobe in lobar pneumonia ( gray hepatization) – lower lobebecome airless, liver like texture, gray white

4 stages of inflammatory response

CongestionRed hepatizationGray hepatizationResolution

Stage of congestion

Lung – heavy, boggy, redVascular engorgementIntra-alveolar fluid with few neutrophils& often numerous bacteria

Stage of red hepatization

Massive confluent exudation with red cells, neutrophils and fibrin filling the alveolar spacesGross – lobe appear distinctly red, firm & airless with liver-like consistency

Stage of red hepatization

Stages of gray hepatization

Progressive disintegration of red cells Persistence of fibrinosuppurativeexudatesGross – grayish brown, dry surface

Stages of gray hepatization

Stage of resolution

Consolidated exudates within alveolar spaces undergoes progressive enzymatic digestion to produce a granular, semi fluid debris Resorbed & ingested by macrophages, coughed up or organized by fibroblasts growing into it

Stage of resolution

Bronchopneumonia

Patchy consolidation of lung May be one lobe or multilobarFrequently bilateral & basal

Gross

3 to 4 cm in diameterSlightly elevated, dry, granular, gray-red to yellow Poorly delimited at margin

Histology Suppurative, neutrophil-rich exudates that fills bronchi, bronchioles and adjacent alveolar spaces

At higher magnification, the pattern of patchy distribution of a bronchopneumonia is seen.

Bronchopneumonia

Viral and Mycoplasmal Pneumonia(Community acquired atypical pneumonia)

Morphology

Patchy or whole lobe Bilateral or unilateralRed-blue, congested & subcrepitantPleuritis or pleural effusion is infrequent

Viral and Mycoplasmal Pneumonia(Community acquired atypical pneumonia)

HistologyInflammatory reaction in interstitial tissue, virtually within the walls of alveoliAlveolar septa – widened, edematousMononuclear infiltrates of L, H, P & N in acute casesAlveoli – free of exudatesPink hyaline membrane in alveolar walls

Complication of pneumonia

1. Abscess formation- due to tissue destruction & necrosis

2. Empyema- spread of infection to pleura cavity causing intra-pleural fibrinosuppurativereaction

Complication of pneumonia

3. Organization of exudates- convert portion of lung into solid tissue with fibrous scar

4. Bacterial dissemination to heart valves, pericardium, brain, kidneys, spleen, joints resulting metastatic abscesses, endocarditis, meningitis, suppurativearthritis

Clinical features

Abrupt onset of high fever with chillsProductive coughMucopurulent sputumPleuritic pain & friction rubRadiologic appearance - well circumscribed radio-opacity in LP- focal opacities in BP

SUPPURATIVE LUNG DISEASES

BronchiectasisLung abscessEmpyema

BRONCHIECTASIS

Definition Disease characterized by permanent dilatation of bronchi & bronchiolescaused by destruction of the muscle & elastic tissue, resulting from or associated with chronic necrotizing infection

Etiology

Obstruction & infection – major cause- obstruction (mucus, tumor, FB) →impaired normal clearing mechanism →pooling of secretion distal to obstruction → inflammation of airwaysSevere infection → necrotizing fibrosis and eventually dilatation of airways

Etiology

Congenital or hereditary- cystic fibrosis- intralobular sequestration of the lung- immunodeficiency state- primary ciliary dyskinesia- Kartagener syndrome

Morphology

Lower lobes, bilaterallyVertical air passagesMost severe in more distal bronchi & bronchioles

Gross

Airways – dilated, up to 4 timesLong, tube-like enlargement of airways → cylindrical bronchiectasisFusiform or saccular distension →saccular bronchiectasisDilated airways can be followed directly out to pleural surfacesOn C.S → cysts filled with mucopurulentsecretions

Bronchiectasis

Bronchial tubes are extremely dilated with thicken, fibrotic wall. Adjacent lung is almost completely destroyed

Focal area of dilated bronchi with bronchiectasis.

Bronchiectasis

Histology

Full-blown, active case → intense acute & chronic inflammatory exudation within the walls of bronchi & bronchiolesDesquamation of lining epitheliumExtensive areas of necrotizing ulceration

Clinical course

CorpulmonaleLung abscessMetastatic brain abscessesAmyloidosis

LUNG ABSCESS

Definition

A local suppurative process within the lung, characterized by necrosis of lung tissue

Etiology & Pathogenesis

Oropharyngeal surgical procedures, sinobronchial infection, dental sepsis, bronchitis

Aerobic & anaerobic streptococci , Staphylococcus aureus, GN organisms

Mechanisms

Aspiration of infective material in acute alcoholism, coma, anesthesia, sinusitis, gingivodental sepsis, debilitation →cough reflexes depressedAntecedent primary bacterial infection →post-pneumonic abscess, fungal infection, bronchiectasisSeptic embolismNeoplasiaMiscellaneous

Morphology

Size -few mm to large cavities of 5-6 cmSingle or multipleAbscess due to aspiration → more common on right ( more vertical right main bronchus ) and more singleAbscess from pneumonia or bronchiectasis → usually multiple, basal, diffusely scattered

Morphology

Cavity filled with suppurative debrisIf communication with air passage →partially drain → air-containing cavity Continued infection → large, fetid, green-black, multilocular cavities (gangrene of the lung)Suppurative destruction of lung parenchyma within central area of cavitation

Seen here are two lung abscesses, one in the upper lobe and one in the lower lobe of this left lung.

abscessing bronchopneumonia in which several abscesses with irregular, rough-surfaced walls are seen within areas of tan consolidation.

• Old pulmonary abscess cavity. • Multiloculated with delicate strands of fibrous tissue crossing the space. • No evidence of acute inflammation in the wall • Fairly normal surrounding lung.

Course

Most resolve with antimicrobial therapyExtension of infection into pleural cavity → empyemaHemorrhage Septic emboli → brain abscess,meningitisSecondary amyloidosis

EMPYEMA

Collection of pus in pleural cavitySuppurative pleuritisPresence of purulent pleural exudatesCharacterized by loculated, yellow-green, creamy pus composed of neutrophils admixed with other leukocytes

Etiology

Contiguous spread of organisms from intrapulmonary infectionLymphatic disseminationHaematogenous disseminationDirect extension of infection below diaphragm (subdiaphragmatic or liver abscess) especially on right side

Clinical course

May resolve by antibiotics

Obliterate pleural space or envelope the lungs → embarrass pulmonary expansion