Morphologic Changes in Lobar Pneumonia A classic example of acute inflammation.It involves FOUR STAGES:1st STAGE: STAGE OF CONGESTION: This 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 2nd STAGE: STAGE OF RED HEPATIZATION: It last for a few days. In the alveolar spaces there is massive accumulation of neutrophils together with macrophages and lymphocytes. Numerous red blood cells are also extravasated from the capillaries. The lung is red, solid and airless, with a consistency resembling fresh liver.3rd STAGE :GREY HEPATIZATION: It lasts a few days and represents further accumulation of fibrin, with destruction of white cells and red cells. The lung now is gray brown in colour and solid.4th STAGE: RESOLUTION: It occurs at about 8 – 10 days in untreated cases and represents the resorption of exudate and enzymatic digestion of inflammatory debris, with preservation of underlying alveolar wall architecture

Red Hepatization: The congested septal capillaries and extensive neutrophil exudation into alveoli corresponds to early red Hepatization,. Fibrin not yet formed

Gray Hepatization: Advanced organizing pneumonia featuring transformation of exudates to Fibrinomyxoid masses richly infiltrated by macrophages and fibroblasts

CLINICAL COURSE OF PNEUMONIA

-The major symptoms of pneumonia are malaise , fever, cough productive of sputum and chest pain.

- The characteristic radiologic appearance of lobar pneumonia is that of a radiopaque, usually well – circumscribed lobe, whereas broncho- pneumonia shows focal opacities.

Cough with greenish or yellow phlegmFever with shaking chillsSharp chest painRapid, shallow breathingShortness of breath Headache

Excessive sweating Clammy skinLoss of appetiteExcessive fatigueConfusion in elderly people

Radiological findings in Pneumonia

Lobar Pneumonia Broncho Pneumonia

Usually Unilateral Usually Bilateral

Involvement of an entire lobe

Patchy involvement

Uncommon at extreme of ages

More common in infancy and old age

95% cases are due to Strep Pnemococcus

Organisms of less virulence are responsible

Microbiologic association of Pneumonia

1.Pneumonia due to Strep Pneumococcus: Respond readily to Penicillin treatment but there are increasing numbers of Penicillin – resistant strains of Pneumococci

Commercial Pneumococal vaccines containing capsular polysaccharides from the common serotypes of Pneumococcus are available, and their proven efficacy mandates their use in patients at risk for the Pneumococal infections

2. Pneumonia due to Haemophilus Influenzae

Both unencapsualated and capsulated forms are important causes of community - acquired pneumonias.

H. Influenzae is the most common cause of bacterial cause of acute exacerbation of COPD

2. Pneumonia due to Moraxella Catarrhalis It is increasingly being recognized as a cause of pneumonia especially in elderly.3. Pneumonia due to Staph Aureus: It is an important cause of secondary bacterial pneumonia in children and healthy adults following viral respiratory illness (e.g., measles in children and influenza in both children and adults).

It is associated with a high incidence of complications , such as lung abscess and empyema

Staphylococcal pneumonia is also an important cause of nosocomial pneumonia

5. Pneumonia due to Klebsialla Pneumonia

It is the most common cause of gram – negative bacterial pneumonia .

It frequently afflicts debilitated and malnourished persons particularly chronic alcoholics.

Thick and gelatinous sputum is characteristic because the organism produces an abundant viscid capsular polysaccharide, which the patient may have difficulty in coughing up.

6. Pneumonia due to Pseudomonas Aeruguinosa

It is most commonly seen in nosocomial settings

It is also common in patients who are neutropenic, usually secondary to chemotherapy ; in patients with extensive burns; and in those requiring mechanical ventilation

7. Pneumonia due to Legionella Pneumophilia:It is the agent of Legionnaire’s Disease ,an eponym for the epidemic and sporadic forms of pneumonia caused by this organism.

It flourishes in artificial aquatic environments such as water – cooling towers and within the tubing system of domestic (portable) supplies.

The mode of transmission is thought to be either inhalation of aerosolized organisms or aspiration of contaminated drinking water Can be severe ; In immunocompromised the fatality rate is 30% to 50% PONTIAC FEVER Self limiting upper respiratory tract disease caused byLegionella , without Pneumonic features

Special Types of Pneumonias

Community – Acquired Atypical Pneumonias

Nosocomial Pneumonias

Aspiration Pneumonias

Community Acquired Atypical Pneumonias

●Unlike “typical” acute pneumonias , atypical Pneumonia is characterized by:

● Modest amount of sputum ● No Physical findings of consolidation of lung ● White cell counts normal or moderately increased ● May present as a severe upper respiratory tract infection

or “chest cold” that goes undiagnosed OR may present as a fulminant life- threatining infection in immunocompromised patients.

● Organisms responsible are: (i) Mycoplasma Pnuemoniae (most common) (ii) Viruses ( most importantly Influenza virus) (iii) Chlamydia Pneumoniae (iv) Rickettsiae

The term “ATYPICAL” denotes the moderate amounts of sputum, absence of physical findings of consolidation, only moderate elevation of white cells count and lack of alveolar exudates

Morphologic findings in Atypical Pneumonias•The process may be patchy or it may involve whole lobes bilaterally or unilaterally.

• Macroscopically the affected areas are red- blue , congested and subcrepitant.

• Histologically the inflammatory reaction is largely confined within the walls of alveoli. The septa are widened and edematous ; they usually contain a mononuclear inflammatory infiltrate of lymphocytes , histiocytes and occasionally plasma cells.

• In contrast to bacterial pneumonias the alveolar spaces in atypical pneumonias are remarkably free of cellular exudate.

Viral Pneumonias; The thickened alveolar walls are heavily infiltrated with mononuclear leucocytes

Clinical course of atypical pneumonia•The clinical course of atypical pneumonia is extremely varied• May present as a severe upper respiratory tract infection or “chest cold” that goes undiagnosed OR may present as a fulminant life- threatining infection in immunocompromised patients.• Most typically the onset is that of an acute, nonspecifically febrile illness characterized by fever, headache, , malaise, and later cough with minimal sputum.• Chest radiographs usually reveal transient , ill – defined patches , mainly on lower lobes.• Physically findings are characteristically minimal. • Prognosis for a uncomplicated is good; generally complete recovery is the rule.

Typical Pnuemonia Atypical PnuemoniaConsolidation of lung Consolidation is not evident

The major symptoms of pneumonia are malaise , fever, cough productive of sputum and chest pain.

May present as a severe upperrespiratory tract infection or “chest cold”that goes undiagnosed OR may present as a fulminant life – threatininginfection in immunocompromisedpatients

Copious amount of sputum Modest amount of sputum

White cell count is increased; with a predominance of Neutrophils

White cell count is usually normal

Histology: Inflammatory exudates in alveolar spaces;Predominant cell is neutrophil

Histology: the inflammatory infiltrate is largely confined within the walls of alveoli; Predominant cell is Lymphocyte.

X-Ray: Findings of consolidation X- Ray: Transient ill – defined patches