Diagnosis
Pneumonia
Inflammation of the lung parenchyma resulting in consolidation of the affected part and a filling of the alveolar air spaces with exudate, inflammatory cells, and fibrin.
Etiology
Causes [len][cgk]
Virus (common)
Rhinoviruses, Coronaviruses, Influenza virus, Respiratory Syncytial Virus (RSV), Adenovirus, and Parainfluenza
Bacteria (common)
Streptococcus pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Mycoplasma pneumonia, Staphylococcus aureus, Group A Streptococci, Moraxella catarrhalis, Legionella pneumophila, Klebsiella, tuberculosis, Gram-negative bacilli
Fungi (less common)
Histoplasma capsulatum, blastomyces, Cryptococcus neoformans, Pneumocystis jiroveci, Coccidioides immitis and Histoplasmosis
Parasites (less common)
Toxoplasma gondii, Strongyloides stercoralis, Ascaris lumbricoides, and Plasmodium malariae
Drugs
Radiation
Chemical burns
Autoimmune diseases
Idiopathic interstitial pneumonia
Pathophysiology [cgk]
The lower respiratory tract is not a sterile environment and is constantly exposed to environmental pathogens
Mechanical defense: nasal hair and mucus
Chemical defense: alveolar epithelial cell-produced proteins like surfactant
Inflammatory reaction --> fluid from surrounding blood vessels fill the alveoli --> consolidation seen on chest X-ray
The inflammatory response leads to the clinical symptoms of pneumonia:
Activated alveolar macrophages work to engulf and eliminate bacteria
If bacterial growth exceeds host defense capacity --> uncontrolled infection
Fever, cough, dyspnea, and chest pain
Classification of bacterial pneumonia:
Community-acquired pneumonia
Hospital-acquired pneumonia: Develops after 48 hours of hospitalization
Atypical pneumonia: Caused by a pathogen not detectable by traditional Gram stain or standard cultures
Ventilator-associated pneumonia
Risk factors [iz8]
Altered consciousness --> risk of aspiration (alcoholism, seizure disorders, drug use)
Smoking
Immunodeficiency
COPD
Kidney disease
Liver disease
PPI
Dysphagia
Age
Complications [cgk]
Lung fibrosis
Necrotizing pneumonia
Empyema
Pulmonary abscess
Meningitis
Sepsis
Acute respiratory distress syndrome
Multiple organ failure
Epidemiology
Incidence per 100.000 [gh6][pok][iz8][4sp][8qd][yoa][d6r]
Symptoms & findings
Symptoms
Chills, Confusion, Cough, Crepitations, Cyanosis, Decreased consciousness, Diarrhea, Dyspnea, Fatigue, Fever, Headache, Hemoptysis, Hypotension, Hypothermia, Intercostal retraction, Lymphadenopathy, Myalgia, Respiratory distress, Respiratory failure, Seizure, Tachycardia, Tachypnea, Vomiting, Wheezing
Clinical findings
Acidosis, Elevated CRP, Elevated Lactate, Hypoxemia, Leukocytosis, Pleural effusion, Pulmonary infiltrate
Anamneses
None listed.
Localized findings
Approach
Blood test
Blood gas
Urine serelogy
Sputum culture
Chest x-ray
CT thorax
Bronchoscopy
Transtracheal Aspiration
Thoracentesis
Biopsy
Treatment
Prophylaxis: pneumococcal vaccine
Supportive measures include the following: [len][cgk]
Analgesia and antipyretics
Chest physiotherapy
Intravenous fluids
Diuretics
Oxygen supplementation
Positioning of the patient to minimize aspiration risk
Bronchodilators
N-acetylcysteine
Suctioning and bronchial hygiene
Ventilation with low tidal volumes (6 mL/kg of ideal body weight)
Nutrition
Early mobilization
Antibiotic therapy:
Non-ICU patients:
Beta-lactam + Doxycycline/Macrolide
ICU patients:
Beta-lactam + antipneumococcal Quinolone/Macrolide
Streptococcus pneumoniae:
1st line: Penicillin G, Amoxicillin
Alternatives: Macrolide, Cephalosporin, Clindamycin, Doxycycline
Penicillin resistant: Vancomycin, Linezolid, Amoxicillin (3 g/d)
Staphylococcus aureus:
1st line: Antistaphylococcal penicillin
Alternatives: Cefazolin, Clindamycin
Methicillin resistant: Vancomycin, Linezolid, Trimethoprim-Sulfamethoxazole
Haemophilus influenzae:
1st line: Amoxicillin
Alternative: Fluoroquinolone, Doxycycline, Azithromycin, Clarithromycin
Beta-lactamase: 2nd/3rd generation Cephalosporin, Amoxicillin/Clavulanate, Fluoroquinolone, Doxycycline, Azithromycin, Clarithromycin
Mycoplasma pneumoniae: Macrolide, Tetracycline, Fluoroquinolone
Chlamydophila pneumoniae: Macrolide, Tetracycline, Fluoroquinolone
Legionella species: Fluoroquinolone, Azithromycin, Doxycycline
Chlamydophila psittaci/Coxiella burnetii: Tetracycline, Macrolide
Francisella tularensis: Doxycycline, Gentamicin, Streptomycin
Yersinia pestis: Streptomycin, Gentamicin, Doxycycline, Fluoroquinolone
Bacillus anthracis: Ciprofloxacin, Levofloxacin, Doxycycline, Fluoroquinolone, Rifampin, Clindamycin, Chloramphenicol
Enterobacteriaceae: 3rd generation Cephalosporin, Carbapenem, Fluoroquinolone
Pseudomonas aeruginosa: Antipseudomonal beta-lactam + Ciprofloxacin, Levofloxacin, Aminoglycoside
Bordetella pertussis: Macrolide, Trimethoprim-Sulfamethoxazole
Anaerobe: Beta-lactamase inhibitor, Clindamycin, Carbapenem
Corticosteroids (controversial)
Differential diagnoses
Acute respiratory distress syndrome, Asthma, Atelectasis, Bronchiectasis, Bronchiolitis, Bronchitis, COPD, Croup, Epiglottitis, Foreign body, Interstitial lung disease, Lung abscess, Lung cancer, Myocardial infarction, Pneumonitis, Pulmonary edema, Pulmonary embolism, Respiratory failure, Sepsis, Shock, Syndrome of inappropriate antidiuretic hormone secretion
References
[1] http://emedicine.medscape.com/article/300157 (2014-01-02); [Medscape]
[2] Sattar SBA, Nguyen AD, Sharma S. Bacterial Pneumonia. [Updated 2024 Feb 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513321/
[3] Ramirez JA, Wiemken TL, Peyrani P, Arnold FW, Kelley R, Mattingly WA, Nakamatsu R, Pena S, Guinn BE, Furmanek SP, Persaud AK, Raghuram A, Fernandez F, Beavin L, Bosson R, Fernandez-Botran R, Cavallazzi R, Bordon J, Valdivieso C, Schulte J, Carrico RM; University of Louisville Pneumonia Study Group. Adults Hospitalized With Pneumonia in the United States: Incidence, Epidemiology, and Mortality. Clin Infect Dis. 2017 Nov 13;65(11):1806-1812.
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[6] Miyazaki T, Hirano K, Ichihara K, Gonzalez E, Gessner BD, Isturiz RE, Zhang P, Gray S, Pride M, van der Linden M, Jodar L, Maeda T, Kohno S, Arguedas A, Goto City Pneumococcal Pneumonia Incidence Study Group. Community-Acquired Pneumonia Incidence in Adults Aged 18 Years and Older in Goto City, Japan: A Prospective Population-Based Study. CHEST Pulmonary Volume 1, Issue 2, September 2023, 100007.
[7] Theilacker C, Sprenger R, Leverkus F, Walker J, Häckl D, von Eiff C, Schiffner-Rohe J. Population-based incidence and mortality of community-acquired pneumonia in Germany. PLoS One. 2021 Jun 15;16(6):e0253118.
[8] Sun Y, Li H, Pei Z, Wang S, Feng J, Xu L, Gao P, Cao B, Zhan S. Incidence of community-acquired pneumonia in urban China: A national population-based study. Vaccine. 2020 Dec 14;38(52):8362-8370.
[9] https://data.unicef.org/topic/child-health/pneumonia/
[10] DeAntonio R, Yarzabal JP, Cruz JP, Schmidt JE, Kleijnen J. Epidemiology of community-acquired pneumonia and implications for vaccination of children living in developing and newly industrialized countries: A systematic literature review. Hum Vaccin Immunother. 2016 Sep;12(9):2422-40.