A bronchial washing is a diagnostic procedure that collects fluid samples from your large airways to check for lung cancer, infections like tuberculosis and pneumonia, and other lung diseases. It’s performed during a bronchoscopy, where a doctor threads a thin, flexible scope into your airways, squirts a small amount of sterile salt water, and then suctions it back out along with cells, mucus, and microorganisms from the airway walls. The recovered fluid goes to a lab for analysis.
Conditions It Helps Diagnose
Bronchial washing serves two broad purposes: detecting cancer cells and identifying infections. On the cancer side, a lab examines the recovered fluid under a microscope for abnormal cells. This is called cytology, and it picks up malignant cells in roughly 43% of peripheral lung cancer cases (ranging from 12% to 65% depending on the tumor’s location and size). That number is lower than tissue biopsy or brushing, so bronchial washing is typically used alongside those techniques rather than on its own.
For infections, the fluid can be cultured to identify bacteria, fungi, and viruses. Common pathogens found this way include Klebsiella pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae among bacteria. Fungal organisms like Candida albicans and Aspergillus are also detectable, as is Pneumocystis jirovecii, a fungus that causes serious pneumonia in people with weakened immune systems. Tuberculosis can be identified as well, particularly in patients whose sputum samples came back negative.
Your doctor may order this procedure if you have a persistent cough that won’t resolve, difficulty breathing, or coughing up blood. It’s also commonly done when a chest X-ray or CT scan shows something abnormal in the lungs that needs a closer look.
How It Differs From Bronchoalveolar Lavage
Bronchial washing and bronchoalveolar lavage (BAL) are related but distinct procedures, and the terms are sometimes used interchangeably, which causes confusion. The key difference is where in the lung each one samples and how much fluid is used.
A bronchial washing targets the major airways (the trachea down to the segmental bronchi) using about 20 to 40 mL of saline. The scope isn’t wedged tightly into a small airway, so the sample represents the larger breathing tubes. Some contamination from the upper airways is unavoidable with this approach.
BAL goes deeper. The bronchoscope is pushed into a smaller airway and wedged snugly into place, sealing off that section. Then 150 to 300 mL of saline is flushed in and retrieved, pulling cells and organisms from the tiny bronchioles and air sacs (alveoli) deep in the lung. This makes BAL better suited for diagnosing interstitial lung diseases and infections that don’t typically colonize the upper airways. For suspected tuberculosis in patients with negative sputum smears, BAL has shown sensitivity around 85% with near-perfect specificity.
In practice, your pulmonologist may perform both during the same bronchoscopy session, collecting a bronchial washing from the large airways first and then advancing the scope for a BAL if deeper samples are needed.
What the Procedure Feels Like
Bronchial washing is done as part of a bronchoscopy, which typically takes 15 to 30 minutes. You’ll receive a numbing spray (usually lidocaine) in your nose, throat, and vocal cords so you don’t gag or cough as the scope passes through. Many centers also offer intravenous sedation to help you relax, though the procedure can be safely done without it.
The bronchoscope itself is thin, with an outer diameter of 3 to 6 mm, roughly the width of a pencil. Once it reaches the target area in your airways, the doctor injects small amounts of saline through the scope and then gently suctions the fluid back. You may feel a mild urge to cough during the washing. The recovered fluid, which now contains airway cells and any organisms present, is sent to the lab in separate containers for cytology and microbiology testing.
Preparation and Fasting
Because sedation is typically involved, you’ll need to stop eating solid food at least 6 hours before the procedure. Clear liquids like water, black coffee, or apple juice are generally allowed up to 2 hours beforehand. Fatty or fried foods may require 8 or more hours of fasting. Your medical team will give you specific instructions about which medications to take or pause that morning, particularly blood thinners.
You’ll also need someone to drive you home afterward if you receive sedation, since the effects can linger for several hours.
Getting Your Results
Cytology results, which tell your doctor whether abnormal or cancerous cells are present, are typically available within about 2 business days. Microbiology cultures take longer because bacteria and fungi need time to grow in the lab. Standard bacterial cultures usually come back within 3 to 5 days, while tuberculosis cultures can take several weeks because the organism grows slowly. Your doctor may receive preliminary results sooner if rapid staining or molecular testing is used.
Risks and Safety
Bronchial washing is considered minimally invasive and carries a low complication rate. The most common side effects are mild coughing during and after the procedure, a temporary sore throat, and slight hoarseness. Minor bleeding can occur if the airway lining is irritated by the scope, but serious bleeding is rare. Because the washing uses a relatively small volume of saline (20 to 40 mL), it’s gentler on the lungs than a full BAL, which uses several times more fluid. A brief, low-grade fever in the hours after the procedure is not uncommon and usually resolves on its own.