Pulmonary Infection

pneumonia

Definition • Pneumonia is acute inflammation of the lung, usually due to infection affecting distal airways,especially alveoli,with the formation of inflammatory exudates.

Classification • Etiological agent – Bacterial – Viral – Fungal – Others: mycoplasma

• Other criteria – Clinical circumstances – Host reaction – Anatomical pattern

Bacterial Pneumonias Definition

Bacterial pneumonia is a generic term that refers to inflammation and consolidation (solidification) of the lung parenchyma evoked by bacteria invasion. •Consolidation — A process of becoming solid and firm because air spaces are filled with exudate.

• classification: – Lobar pneumonia – Lobular pneumonia (Bronchopneumonia)

Lobar pneumonia • Lobar pneumonia is an acute bacterial infection of a large portion of a lobe or an entire lobe.

• Etiology – 90%~95% of lobar pneumonias are caused by pneumococci (Streptococcus pneumoniae). – Klebsiella pneumoniae, staphylococci, streptococci, H. Influenza are occasional cause.

• Incidence: It occurs in typically otherwise healthy adults between 20 and 50 years of age.

Morphology • Four stages: – Congestion – Red hepatization – gray hepatization – Resolution

The stage of congestion • Macroscopically – the affected lobe(s) is(are) heavy, boggy, red.

Red, edematous

The stage of congestion • Histologically – Alveolus walls vascular congestion and dilation – alveoli contain protein-rich edema fluid, scattered neutrophils and numerous bacteria

The stage of red hepatization • Macroscopically – the lung lobe is distinctly red, firm and airless with liver-like consistency.

consolidation of all or the majority of a lobe of the lung

• Red • Solid • Consistency resembling fresh liver

The stage of red hepatization • Histologically – Alveolar wall vascular congestion becomes more evident – the alveolar spaces are packed with red cells, fibrin and neutrophils. – the pleura usually demonstrates a fibrinous or fibrinopurulent exudate (plueritis).

The stage of gray hepatization • Macroscopically – the lung is dry 、 gray 、 firm and liver-like in consistency.

gray hepatization in the lower lobe of the lung

• Dry Pale

Firm

The stage of gray hepatization • Histologically – Alveolus wall vascular congestion diminishes – the fibrinous exudate, neutrophils persist and increase within alveoli – the number of RBC relatively reduces (disintegration) – The pleuritis is most intense.

　　　　　　图注：大叶性肺炎 灰色肝变期，肺泡腔完整，肺泡隔内毛细血管明显扩张充 血。腔内渗出的纤维素网络了大量的中性粒细胞。 　　

　

灰色肝样变期 ( 低倍 )

灰色肝样变期 ( 高倍 )

The stage of resolution • Macroscopically – the lung is edematous (boggy and wet).

• Histologically – Alveolus wall vascular congestion reoccurs – Exudates within the alveoli are enzymatically digested and either reabsorbed or expectorated, leaving the basic architecture intact. – The pleural reaction may similarly resolve or undergo organization, leaving fibrous thickening or permanent adhesions.

Clinical Course • The onset is abrupt, with high fever and an episode of a severe shaking chill • Chest pain • A cough productive of rusty-colored purulent sputum (when?) • Dyspnea

Complications • Suppurative pleuritis • Pulmonary carnification: organization of the exudate • Bacteremic dissemination: may cause septicemia, pyemia or infective shock • Lung abscess

Pulmonary carnification

Lobular pneumonia • Lobular pneumonia has a characteristic patchy distribution, centered on inflamed bronchioles and bronchi with subsequent spread to surrounding alveoli. Because lobule is made of bronchiole and surrounding alveoli, we also call lobular pneumonia bronchopneumonia.

Etiology • The common agents are staphylococci, streptococci, pneumococci, Haemophillus influenza, Pseudomonas aeruginosa, etc.

Incidence • These people are vulnerable because of lower defensive mechanism. – Infants • With whooping cough, measles.

– The old age • With influenza, chronic bronchitis, etc.

– People suffering from chronic debilitating illness or immunosuppression

Morphology • Macroscopically – foci of inflammatory consolidation are distributed in patches throughout one or several lobes, most frequently bilateral and basal. – The lesions are gray-red to yellow, varying in size up to 0.5 to 1 cm in diameter, poorly delimited in margin. – in severe cases, they may confluent. – The surrounding areas of consolidation is usually hyperemia and edematous, but the large intervening areas are generally normal.

Bronchopneumonia

Morphology • Histologically – focal suppurative exudate fills the bronchi 、 bronchioles and adjacent alveolar spaces. – The centers of suppurative lesions lie in bronchi and bronchioles.

Clinical course • The onset is insidious, often overshadowed by the predisposing condition. • Low-grade fever • Cough with purulent sputum • Course is irregular, lying on the treatment and patient’s condition. • Most can be cured.

Complications • • • •

Respiratory failure Heart failure Pyemia Abscess

小叶性肺炎并发肺脓肿