Bronchopneumonia

# Historical Perspective
- Pneumonia was first recognized by Hippocrates. It was first identified and described by Laennec in 1819.
- In 1842, Rokitansky differentiated Pneumonia into Bronchopneumonia and Lobar Pneumonia.

# Classification
- Pneumonia may be classified according to anatomic distribution of consolidation into two subtypes/groups:
Lobar
Lobular (Bronchopneumonia)
- Lobar
- Lobular (Bronchopneumonia)

# Pathophysiology
- The pathogenesis of Bronchopneumonia is characterized by inflammation of lung parenchyma.
- On gross pathology, multiple foci of consolidation is a characteristic feature of Bronchopneumonia. They are present bilaterally, most commonly in the basal lobes. These lesions are 2-4 cm in diameter, grey-yellow, dry, often centered by a bronchia, are poorly delimited and have the tendency to confluence, especially in children.
- On microscopic histopathological analysis, a focus of inflammatory condensation, centered by a bronchiola with acute bronchiolitis is a characteristic finding in Bronchopneumonia. In addition, alveolar lumens surrounding the bronchia are filled with neutrophils and suppurative exudate("leukocytic alveolitis"), massive congestion is present and inflammatory foci are separated by normal, aerated parenchyma.
- Bronchopneumonia is most commonly caused by pneumococcal serotypes 3, 7,8,10,18 and 20.
- Common mechanisms in development of pneumonia include, micro-aspiration, hematogenous spread, spread from a contiguous focus and macro-aspiration.
- Bronchopneumonia is usually associated with infections due to gram-negative bacteria, Staphylococcus aureus and some fungi.

# Clinical Features
- Common clinical findings in Bronchopneumonia include cough, fever, chills, dyspnea, pleuritic chest pain and sputum production. However, many of these features may be absent in older patients.
- Bronchopneumonia can also case Gastrointestinal symptoms such as nausea, vomiting and diarrhea.
- Older patients may also present with altered mental status.

# Differentiating Bronchopneumonia from other Diseases
- Lobular pneumonia must be differentiated from other diseases that cause similar clinical symptoms and interstitial infiltrates on chest x-ray such as:
- Lobar pneumonia
- Non-infectious lung conditions such as: Hypersensitivity pneumonitis, Collagen vascular disease, Asbestosis, Drug toxicities, Pulmonary fibrosis, Pulmonary edema, Pulmonary embolism and neoplastic lesions.
- Other types of pneumonias such as: cryptogenic pneumonia.

# Epidemiology and Demographics
- The rate of Community acquired pneumonia is approximately 5.16-7.06 cases per 1000 individuals per year.

## Age
- Patients of all age groups may develop Bronchopneumonia.
- Bronchopneumonia is more commonly observed among elderly patients.

## Gender
- Brochopneumonia is more commonly observed in men than women.

## Race
- Bronchopneumonia is more commonly observed in Black persons than caucasians.

# Risk Factors
- Common risk factors in the development of Bronchopneumonia are Influenza infection, Alcohol abuse, Hyposplenism/splenectomy, smoking, COPD/Asthma and Immunocompromise. Additional risk factors include, homelessness, incarceration, pregnancy, crack cocaine use, opioid use and occupational welding.
- Risk factors for a complicated course include, older age, preexisting lung condition, immunodeficiency/AIDS, and acquisition of a nosocomial infection.

# Natural History, Complications and Prognosis
- Early clinical features include sudden fever, chills, cough and chest pain.
- If left untreated, patients with Bronchopneumonia may progress to develop tachypnea and increasing systemic toxicity. They may also progress to develop Lobar pneumonia.
- Common complications of Bronchopneumonia include parapneumonic effusion, empyema, necrotizing pneumonia, lung abscess and metastatic infections such as endocarditis, septic arthritis, peritonitis, pericarditis and meningitis, and other cardiac complications.

# Diagnosis

## Diagnostic Study of choice
- The diagnosis is made when clinical and radiological evidence suggests the presence of Bronchopneumonia.

## Symptoms
- Symptoms of Bronchopneumonia may include the following:
Fever
Chills
Cough
Chest Pain
Shortness of breath
- Fever
- Chills
- Cough
- Chest Pain
- Shortness of breath

## Physical Examination
- Physical examination may be remarkable for:
Fever
Respiratory rate >24 breaths/min (Tachypnea)
Tachycardia
Chest Examination:
Audible crackles
Decreased or bronchial breath sounds
Dullness to percussion in areas of consolidation
Tactile fremitus
Egophony
- Fever
- Respiratory rate >24 breaths/min (Tachypnea)
- Tachycardia
- Chest Examination:
Audible crackles
Decreased or bronchial breath sounds
Dullness to percussion in areas of consolidation
Tactile fremitus
Egophony
- Audible crackles
- Decreased or bronchial breath sounds
- Dullness to percussion in areas of consolidation
- Tactile fremitus
- Egophony

## Laboratory Findings
- There are no specific laboratory findings associated with Bronchopneumonia.
- A leukocytosis (15000-30000 per mm3)  with a left ward shift on a blood test can aid in diagnosis of Bronchopneumonia.
- An elevated concentration of ESR or CRP is a non-specific indication of inflammation in the body.

## Imaging Findings
- Chest x-ray is the imaging modality of choice for Bronchopneumonia.
- On chest x-ray, Bronchopneumonia is characterized by peribronchial thickening and poorly defined air-space opacities. Inhomogeneous patchy areas of consolidation involving several lobes reflect more severe disease. When confluent, bronchopneumonia may resemble lobar pneumonia.
- In the case of a negative chest x-ray and a high clinical suspicion, HRCT scan may be used to confirm the diagnosis as it has a higher sensitivity and accuracy in detecting lesions and anatomical changes.
- In case of emergency where chest x-ray and HRCT cannot be performed, lung ultrasound performed by an experienced physician can yield findings.

## Other Diagnostic Studies
- Microbial analysis in Bronchopneumonia can be performed using techniques such as Blood culture, Sputum analysis, PCR and Urine antigen detection, however, pathogens are not commonly identified and empiric treatment should be started once the diagnosis is made.

# Treatment

## Medical Therapy
- The mainstay of therapy for Bronchopneumonia is antibiotics and supportive care.
- Choice of antibiotics is dependent on epidemiology of microbes, resistance and patients' co-morbidities and severity of illness.
- In patients without co-morbidities Macrolides such as Azithromycin and Clarithromycin can be used. In the case of Macrolide resistant pneumonias and patients with multiple co-morbidities, Doxycycline, Amoxicillin-Clavulanate, and Cephalosporins such as Cefpodoxime and Cefuroxime may be used.
- Response to antibiotics can be monitored with clinical improvement, serum inflammatory markers and chest x-ray findings. However, most non-complicated pneumonias are treated out-patient and only require two follow up treatments to clinically determine improvement and resolution of the pneumonia, respectively. Follow-up chest x-rays are only required in male patients over the age of 50 years and smokers.

## Prevention
- Effective measures for the primary prevention of Bronchopneumonia include vaccination against influenza and pneumococcal antigens, and smoking cessation. Pneumococcal vaccination is indicated in patients over the age of 65 years.