Bronchiectasis is a chronic lung condition characterized by the permanent and abnormal widening of the airways, or bronchi, within the lungs. This damage disrupts the airways’ ability to clear mucus effectively, leading to a vicious cycle of chronic infection, inflammation, and further structural damage to the bronchial walls. The diagnostic process requires a combination of a patient’s clinical history, physical findings, and specific medical tests to both confirm the presence of this structural damage and determine its underlying cause. Early and accurate diagnosis is important for preventing further lung function decline and starting targeted management.
Initial Clinical Assessment
The first step in diagnosing bronchiectasis involves a detailed review of the patient’s medical history and current symptoms. Physicians look for a persistent, wet cough that often lasts months to years, a hallmark symptom that typically involves the daily production of a large volume of sputum. This cough is often described as “wet” because of the excessive mucus, which can sometimes be purulent or contain blood.
The physician will also investigate a history of recurrent respiratory infections that require frequent courses of antibiotics, as well as past events like severe childhood pneumonia or whooping cough (pertussis) that may have initiated the airway damage. During the physical examination, the doctor listens to the chest with a stethoscope for specific sounds. Common findings include crackles and rhonchi, though these physical signs are not always present and are often non-specific.
Measuring Lung Capacity and Airflow
Pulmonary function tests (PFTs) are performed to measure how well the lungs are working, but they are generally used to assess the severity of functional impairment rather than to confirm the structural diagnosis. Spirometry is the most common test, requiring the patient to forcibly exhale to measure the amount of air exhaled and the speed of the exhalation.
The key measurements obtained are the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1). In bronchiectasis, these measurements often reveal an obstructive pattern, characterized by a disproportionate reduction in the FEV1 compared to the FVC, though mixed obstructive-restrictive patterns or even normal function can be seen. PFTs confirm functional limitation and track disease progression, but they do not provide the necessary visual evidence of airway dilation.
High-Resolution CT Scanning
The definitive diagnosis of bronchiectasis relies on imaging, with High-Resolution Computed Tomography (HRCT) scanning considered the gold standard. HRCT provides detailed, cross-sectional images of the lungs, allowing clinicians to visualize the anatomical damage to the bronchi. This advanced imaging is far superior to a standard chest X-ray, which often shows only non-specific changes in early disease.
The key signs doctors look for on the HRCT scan are markers of airway dilation and thickening. One classic finding is the “signet ring sign,” which appears when a dilated bronchus is viewed end-on next to its accompanying, smaller pulmonary artery, resembling a signet ring on a finger. Another common sign is the “tram track” appearance, which are parallel line opacities seen when the thickened, non-tapering walls of the dilated bronchi run alongside each other. The presence of these specific radiological features confirms the irreversible structural damage required for a diagnosis of bronchiectasis.
Testing for Etiology and Infection
Once the diagnosis of bronchiectasis is confirmed by HRCT, the next set of tests focuses on identifying the specific underlying cause and any current infectious agents. Determining the etiology is important because the management of bronchiectasis is often directed at the root cause, such as an immune deficiency or an inflammatory condition.
A sputum culture is routinely performed by collecting a sample of the patient’s mucus to identify specific bacteria, such as Pseudomonas aeruginosa or Haemophilus influenzae, which commonly colonize the damaged airways. Identifying these organisms guides the selection of appropriate antibiotics for current infection or long-term management. Blood tests are also conducted to screen for systemic causes.
Screening for Underlying Causes
Blood tests include measuring serum immunoglobulins (IgG, IgA, IgM) to check for immune deficiencies, or testing for alpha-1 antitrypsin deficiency. For some patients, especially those with severe or early-onset disease, specific testing for cystic fibrosis (CF) via a sweat test or genetic analysis may be necessary.