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Chest infections Pathogens Bacterial pneumonia Streptococcus pneumoniae (pneumococcus) Staphylococcus Pseudomonas Klebsiella Chlaymidia Neisseria meningitides Haemophilus influenzae Anaerobes Legionella Mycoplasma pneumoniae Actinomyces israeli Tuberculosis Viral pneumonia (25% of community-acquired pneumonias) Influenza Varicella, herpes zoster Rubeola CMV Coxsackie, parainfluenza, adenovirus, RSV Fungal pneumonia Histoplasmosis Coccidioidomycosis Blastomycosis Aspergillosis Cryptococcosis Candidiasis Zyogomyocoses Parasitic pneumonias Pnet~mocystis carinii Toxoylasma gondii ACQUISITION OF PNEUMONIA Community-acquired pneumonia S. pneumoniae ,, Haemophilus Mycoplasma Hospital-acquired pneumonia (incidence 1%, mortality 35%): nosocomial infection Gram negatives: Pseudomonas, Proteus, E. coli, Enterobacter, Klebsiella Pneumonia in immunosuppressed patients Bacterial pneumonia (gram negative) still most common TB Fungal PCP(Pneumocystic carinii pneumonia). Endemic pneumonias Fungal: histoplasmosis, coccidioidomycosis, blastomycosis Viral Aspiration-associated pneumonia (important) RISK FACTORS The radiographic appearance of pulmonary infections is variable depending on pathogen, underlying lung disease, risk factors, and prior or partial treatment. Common pathogens associated in community-acquired infections are: Risk Factor Pathogens I Alcoholism ===Gram negatives, Strep. pneumoniae, TB, aspiration (mouth flora) Old age ====Strep. pneumoniae, S. aureus, aspiration Aspiration ====Mouth flora (anaerobes) Cystic fibrosis ==Pseudomonas, S. aureus, Aspergillus Chronic bronchitis ===Strep. pneumoniae, H. influenzae.. Other risk factors for developing pneumonia Bronchiectasis Coma, anesthesia, seizures (aspiration) Tracheotomy Antibiotic treatment Immunosuppression (renal failure, diabetes, cancer, steroids, AIDS) Chronic furunculosis (Staphylococcus) RADIOGRAPHIC SPECTRUM OF PULMONARY INFECTIONS TYPE Pathogen LOBAR PNEUMONIA Infection primarily involves alveolus Spread through pores of Kohn and canals of Lambert throughout a segment and ultimately an entire lobe Bronchi are not primarily affected and remain air-filled; therefore: Air bronchograms No volume loss because airways are open Nowadays uncommon due to early treatment Round pneumonia (children): S. pneumoniae S. pneumoniae K. pneumoniae Others: S. aureus H. influenzae Fungal Type BRONCHOPNEUMONIA Primarily affects the bronchi and adjacent alveoli Volume loss may be present as bronchi fill with exudate Bronchial spread results in multifocal patchy Opacities S. pneumoniae K. pneumoniae Others: S. aureus H. influenzae NODULES Fungal S. aureus Gram negatives Other: H. influenzae Mycoplasma Fungal Histoplasma Aspergillus C yptococcus Coccidi~ides Bacterial Legionella Nocardia Septic emboli S. aureus Variable in size Indistinct margins CAVITARY LESIONS Abscess: necrosis of lung parenchyma t bronchial communication Fungus ball (air crescent sign) Pneumatoceles due to air leak into pulmonary interstitium (S. auueus) Anaerobes Fungal TB DIFFUSE OPACITIES Reticulonodular pattern: interstitial peribronchial areas of inflammation (viral) Viral Mycoplasma Alveolar location (PCP) Miliary pattern: hematogenous spread (TB) PCP Complications of Pneumonia Parapneumonic effusion Stage 1: exudation: free flowing Stage 2: fibropurulent: loculated Stage 3: organization, erosion into lung or chest wall Empyema Bronchopleural fistula (fistula between bronchus and pleural space) with eroding pleural-based fluid collections Bronchiectasis Pulmonary fibrosis, especially after necrotizing pneumonia or ARDS Adenopathy.. RESOLUTION OF PNEUMONIA 80% to 90% resolve within 4 weeks 5% to 10% resolve within 4 to 8 weeks (usually in older or diabetic patients). Subsequent films should always show interval improvement compared to the prior films. Nonclearance Antibiotic resistance Consider other pathogen, (e.g., TB) Recurrent infection Obstruction pneumonitis due to tumor Bacterial Infections Common pathogens S. pneumoniae, 50% (40-60 years) Mycoplasma, 30% Anaerobes, 10% Gram negatives, 5% Staphylococcus, 5% Haemophiltis, 3% (especially in infants and patients with COPD) Clinical findings Pneumonic syndrome Fever Cough Pleuritic pain Sputum Ancillary findings Headache, arthralgia, myalgia Diarrhea Hemoptysis STREPTOCOCCAL PNEUMONIA Radiographic features Lobar or segmental pneumonia pattern Bronchopneumonia pattern Round pneumonia (in children) STAPHYLOCOCCAL PNEUMONIA Radiographic features Bronchopneumonia pattern Bilateral in > 60% Abscess cavities in 25%-75% Pleural effusion, empyema, 50% Pneumatoceles, 50% (check valve obstruction), particularly in children Central lines Sign of endocarditis PSEUDOMONAS PNEUMONIA Typical clinical setting Hospital-acquired infection Ventilated patient Reduced host resistance Patients with cystic fibrosis Radiographic features Three presentations: Extensive bilateral parenchymal consolidation (predilection for both lower lobes) Abscess formation Diffuse nodular disease (bacteremia with hematogenous spread; rare) LEGIONNAIRES' DISEASE Severe pulmonary infection caused by Legionella pneumophila; 35% require ventilation, 20% mortality. Most infections are community acquired. Patients have hyponatremia. Seroconversion for diagnosis takes 2 weeks. Radiographic features Common features Initial presentation starts as peripheral patchy consolidation Bilateral severe disease Rapidly progressive Pleural effusions < 50% Lower lobe predilection Uncommon features Abscess formation Lymph node enlargement HAEMOPHILUS PNEUMONIA Caused by Hnemophilus influenzne. Occurs most commonly in children, immunocompromised adults or patients with COPD. Often there is concomitant meningitis, epiglottitis, bronchitis. Radiographic features Bronchopneumonia pattern Lower lobe predilection, often diffuse Empyema TUBERCULOSIS (TB) Transmitted by inhalation of infected droplets Mycobacterium tuberculosis or M. bovis. TB usually requires constant or repeated contact with sputum-positive patients as the tubercle does not easily grow in the immunocompetent human host. Target population: Patients of low socioeconomic scale (homeless) Alcoholics Immigrants: Mexico, Philippines, Indochina, Haiti Elderly patients AIDS patients Prisoners Primary infection Usually heals without complications. Sequence of events: Pulmonary consolidation (1-7 cm); cavitation is rare; lower lobe (60%) > upper lobes Caseous necrosis 2-10 weeks after infection Lymphadenopathy (hilar and paratracheal), 95% Pleural effusion, 10% Spread of a primary focus occurs primarily in children or immunosuppressed patients Secondary infection (Reactivation TB) Active disease in adults most commonly represents reactivation of a primary focus. However, primary disease is now also common in adults in developed countries since there is no exposure in childhood. Distribution is as follows: Typically limited to apical and posterior segments of upper lobes or superior segments of lower lobes (because high PO,?) Rarely in anterior segments of upper lobes (in contradistinction to histoplasmosis) Consolidation scarring Radiographic features Exudative tuberculosis Patchy or confluent airspace disease Adenopathy is uncommon Fibrocalcific tuberculosis Sharply circumscribed linear densities radiating to hilum Cavitation, 40% Complications Miliary TB may occur after primary or secondary hematogenous spread Bronchogenic spread occurs after communication of the necrotic area with a bronchus; it produces an acinar pattern (irregular nodules approximately 5 mm in diameter) Tuberculoma (1-7 cm): nodule during primary or secondary TB; may contain calcification Effusions are often loculated Bronchopleural fistula Pneumothorax COMPARISON Primary TB Location Appearance Cavitation Adenopathy as only Finding Effusion Miliary pattern Usually bases Focal No Common Common Yes Reinfection TB Upper lobes, sup. segment LL Patchy Frequent NO Uncommon Yes PULMONARY ABSCESS: The spectrum of anaerobic pulmonary infections includes: Abscess: single or multiple cavities > 2 cm, usually with air-fluid level Necrotizing pneumonia: analogous to abscess but more diffuse and cavities <2cm Empyema: suppurative infection of the pleural space, most commonly as a result of pneumonia. Predisposing conditions Aspiration (alcoholism, neurologic disease, coma, etc.) Intubation Bronchiectasis, bronchial obstruction Treatment: Antibiotics, postural drainage Percutaneous drainage of empyema Drainage/resection of lung abscess only if medical therapy fails. Viral Pneumonia Spectrum of disease Acute interstitial pneumonia: diffuse or patchy interstitial pattern, thickening of bronchi, thickened interlobar septae Lobular inflammatory reaction: multiple nodular opacities 5-6 mm (varicella; late calcification) Hemorrhagic pulmonary edema: mimics bacterial lobar pneumonia Pleural effusion: usually absent or small Chronic interstitial fibrosis (broncholitis obliterans). INFLUENZA PNEUMONIA Influenza is very contagious and thus occurs in epidemics. Pneumonia, however, is uncommon. Radiographic features Acute phase: multiple acinar densities Coalescence of acinar densities to diffuse patchy air space disease (bronchopneumonia type). Fungal infection Radiographic features Acute phase: pneumonic type of opacity (may be segmental, nonsegmental, or patchy); miliary (hematogenous) distribution in immunosuppressed patients Reparative phase: nodular lesions with or without cavitations and crescent sign Chronic phase: calcified lymph nodes or pulmonary focus with fungus (e.g., histoplasmosis) Disseminated disease (spread to other organs) occurs primarily in immunocompromised patients.