What Is Bronchoalveolar Lavage?
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Bronchoalveolar Lavage - An Overview

Published on Oct 13, 2022 and last reviewed on Feb 28, 2023   -  4 min read


Bronchoalveolar lavage (BAL) is a minimally invasive procedure by which cells and other components of the bronchi and alveoli are obtained.


BAL is also known as a bronchoalveolar wash. It is a minimally invasive procedure that involves the instillation of sterile normal saline into the tracheobronchial tree. The introduction of a bronchoscope typically facilitates it into the airways. A bronchoscopy is an endoscopic method to visualize the airways directly using a thin, light-weighted, flexible tube that can be advanced quickly into the small airways and bronchioles. BAL plays an important role in the diagnosis of infections and malignancies. It provides samples for various microbiological tests.

What Are the Advantages of Bronchoalveolar Lavage?

One of the significant advantages of BAL is that it prevents the incorrect use of antibiotics. Administration of unnecessary antibiotics is associated with toxicity risks and, thereby, the development of antibiotic resistance. And secondly, it can be carried out as a daycare procedure.

What Are Bronchoalveolar Lavages Used For?

BAL may be used to collect cells and tissues for laboratory testing.

These tests help in diagnosing different lung disorders, such as:

  • Bacterial infections.

  • Fungal infections.

  • Viral infections.

  • Malignancies.

  • Diffuse alveolar hemorrhage.

  • Pulmonary alveolar proteinosis.

How Is the Bronchoalveolar Lavage Performed?

It is typically done by spraying an anesthetic agent down the throat to relax and anesthetize the muscles around, followed by introducing a bronchoscope into the tracheobronchial tree and inspecting the airways, but before any biopsies are collected. This reduces the potential introduction of bronchial wall debris and red blood cells into the most distal airways, which could alter the composition of the lavage.

The bronchoscope is guided into the subsegment of the lung and advanced until the tip of the bronchoscope is wedged into the bronchiole. Sterile normal saline is injected through a handheld syringe and withdrawn back into the syringe. This process is repeated 3-5 times, and up to 300 ml is instilled. If only 5 % of the instilled returns, the procedure should be aborted, whereas if 30 % or more of the instilled returns, it is considered an adequate return.

What Are the Histopathological Findings?

The recovered lavage fluid should be pooled, mixed, and volume recorded, and it should be sent to the laboratory. The BAL fluid cells specimen can remain viable for up to 4hrs at room temperature. The specimen should be routinely processed for microbiology and cytological studies. There are chances of contamination of the BAL specimen by secretions from the oropharynx; semiquantitative culture may help interpret the results.

A large number of oral flora may indicate contamination of the specimen. The specimen is analyzed for cell counts and differential counts, which can be extremely helpful in assessing infection. In addition to culture, other techniques such as polymerase chain reaction (PCR) or special stains may help to identify the pathogens.

Processing of the BAL Fluid on Cellular Analysis:

Typically, BAL fluid obtained from a healthy individual without any underlying lung disease is predominated by 80 % to 90 % of alveolar macrophages, 1 % to 3 % of neutrophils, 5 % to 15 % of lymphocytes, and 1 % of eosinophils, and less than 1 % of mast cells.

Increased Neutrophil Count:

If the neutrophil count is more than 5 %, it indicates:

  • Idiopathic pulmonary fibrosis.

  • Acute respiratory distress syndrome.

  • Infection.

  • Connective tissue disorders.

Increased Eosinophil Count:

The eosinophil count is more than 25 % indicating eosinophilic lung disease.

Increased Lymphocyte Count:

  • If the lymphocyte count is more than 50 %:- it indicates hypersensitivity pneumonitis.

  • If the lymphocyte count is more than 15 %- then clusters of differentiation (CD4/CD8) ratios are assessed.

Elevated CD4/CD8 ratio is seen in the following:

  • Chronic Hypersensitivity pneumonitis.

  • Sarcoidosis.

  • Berylliosis.

  • Asbestosis.

  • Crohn's disease.

  • Connective tissue disorders.

Normal CD4/CD8 ratios are seen in the following:

  • Tuberculosis.

  • Malignancies.

Decreased CD4/CD8 ratios are seen in the following:

An increase in BAL neutrophils has been correlated with the disease severity and prognosis for interstitial pulmonary fibrosis. Increased BAL eosinophils have been associated with more severe disease and worse prognosis in Interstitial pulmonary fibrosis. Likewise, increased neutrophils in BAL patients with sarcoidosis have been associated with a more progressive disease that is less likely to respond to immunosuppressive therapy. BAL lymphocytosis has been correlated to support the diagnosis of sarcoidosis and chronic hypersensitivity pneumonitis. If the BAL findings are non-diagnostic, then transbronchial and surgical lung biopsy play an important role in the diagnosis.

Can Bronchoalveolar Lavage Be Used as a Therapeutic Agent?

The BAL can be used as a therapeutic agent by using small amounts of sterile normal saline to dislodge heavy mucous plugs in the small, distal airways. It is specifically used in the case of pulmonary alveolar proteinosis, which helps remove heavy lipo proteinaceous particles from the lung tissues. Also, in children with refractory Mycoplasma pneumoniae and pneumonia complicated by atelectasis, the therapeutic BAL method has significantly shortened the disease duration, radiographic resolution time, and length of hospital stay.

What Are the Complications of Bronchoalveolar Lavage?

There is little risk in undergoing a bronchoalveolar lavage. The procedure can lead to a sore throat for a few days.

Serious complications are rarely seen but may include,

  • Bleeding in the airways is more likely seen if a biopsy is taken.

  • Fever is commonly seen but not always a sign of infection.

  • A collapsed part of a lung: In rare cases, an airway may be injured during bronchoscopy. If the lung is punctured, it may lead to a collection of air surrounding it, which can cause the lung to collapse.


Bronchoalveolar lavage plays a crucial role in diagnosing and monitoring patients with interstitial lung disease. A combination of physical examination, high-resolution computed tomography (HRCT) imaging, and BAL analysis can provide enough information for the clinician to reach a correct diagnosis and avoid more invasive testing to obtain lung tissue for histopathological examinations. It can be used both as a diagnostic tool and a therapeutic agent, thereby proving itself as a key role in the diagnosis and management of a few disorders.

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Last reviewed at:
28 Feb 2023  -  4 min read




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