I. Introduction & Definition
- Definition: A diagnostic procedure performed during flexible bronchoscopy where saline is instilled into a subsegment of the lung and aspirated back to sample the alveolar and distal airway milieu.
- Concept: Often referred to as a “Liquid Biopsy” of the lower respiratory tract.
- Site: usually performed in the Right Middle Lobe (RML) or Lingula (highest yield due to anatomy), or the most affected area radiologically.
II. Indications
1. Diagnostic Indications
- Non-resolving Pneumonia: To identify resistant bacteria, fungi (Aspergillus), or Pneumocystis jirovecii (PCP).
- Immunocompromised Host: Evaluation of opportunistic infections.
- Interstitial Lung Disease (ILD): To determine cellularity (lymphocytic vs. neutrophilic) or identify hemorrhage.
- Aspiration Syndromes: Detection of lipid-laden macrophages.
- Pulmonary Hemorrhage: Diagnosis of Diffuse Alveolar Hemorrhage (DAH).
2. Therapeutic Indications
- Pulmonary Alveolar Proteinosis (PAP): Whole lung lavage to wash out surfactant protein accumulation.
- Mucus Plugging: To dislodge tenacious plugs (e.g., in severe Asthma or Cystic Fibrosis).
III. Procedure (Technique)
- Wedging: The bronchoscope tip is wedged into a segmental or subsegmental bronchus.
- Instillation: Sterile non-bacteriostatic saline is instilled.
- Dose: 1 ml/kg per aliquot (usually 3 aliquots).
- Aspiration: Gentle suction is applied to retrieve the fluid (effluent).
- Adequacy: >40% recovery of instilled volume is considered adequate.
IV. Analysis and Interpretation
The fluid is sent for Microscopy, Culture, Cytology, and PCR.
1. Normal Pediatric BAL Profile
- Macrophages: 80–90% (Predominant cell type).
- Lymphocytes: <10%.
- Neutrophils: <3%.
- Eosinophils: <1%.
2. Abnormal Patterns
| Finding | Differential Diagnosis |
|---|---|
| Neutrophilia (>50%) | Bacterial pneumonia, Aspiration, Cystic Fibrosis. |
| Lymphocytosis (>15%) | Hypersensitivity Pneumonitis, Sarcoidosis, Viral infection, TB. |
| Eosinophilia (>5%) | Asthma, ABPA, Parasitic infection, Drug reaction. |
| Hemosiderin-laden Macrophages | Diffuse Alveolar Hemorrhage (DAH), Idiopathic Pulmonary Hemosiderosis. |
| Lipid-laden Macrophages | Chronic Aspiration (sensitive but non-specific). |
| Milky/Opaque Fluid | Pulmonary Alveolar Proteinosis (PAP). |
| Silver Stain (+) | Pneumocystis jirovecii Pneumonia (PCP). |
V. Complications
- Transient Fever: Most common (10–30% of cases) due to cytokine release.
- Hypoxemia: Transient drop in SpO2 during and immediately after the procedure.
- Bronchospasm.
- Bleeding: Usually minor/self-limiting.