endobronchial ultrasound

Endobronchial ultrasound (EBUS) puts an ultrasound probe on the tip of a bronchoscope so the operator can see through the airway wall. The airway lining is opaque to the eye, but ultrasound passes through it, revealing the structures pressed up against the outside — especially the lymph nodes and vessels of the mediastinum, the central compartment between the lungs. It is like using a stud-finder against a wall to locate what lies just beyond.

Its signature use is real-time needle sampling of mediastinal lymph nodes. The operator watches the target node on the ultrasound image and advances a fine needle through the airway wall straight into it, aspirating cells under live guidance and steering clear of the nearby blood vessels the ultrasound also shows. This is the technique known as EBUS-guided transbronchial needle aspiration.

EBUS transformed lung-cancer staging because it samples the mediastinal nodes that decide whether a cancer is surgically curable, doing so through the airway without an incision. It has largely replaced the older surgical approach (mediastinoscopy) for first-line nodal staging in many centres, and is also used to diagnose enlarged nodes from sarcoidosis, tuberculosis and other conditions. Its main limit is that it reaches only nodes adjacent to the central airways.