Endobronchial Ultrasound (EBUS) Biopsy of Mediastinal Lymph Nodes
Mediastinoscopy is the ‘gold standard’ method for determining the presence of nodal metastases in the mediastinum. Generally performed as an outpatient surgical procedure, it is associated with a low rate of serious adverse effects (<1%) and the procedure is highly accurate, with false negative rates reported to be between 6% and 9%. Endobronchial ultrasound (EBUS) guided fine needle aspiration biopsy of mediastinal nodes offers a less invasive alternative for histologic sampling of the mediastinal nodes. The procedure has been widely adopted by pulmonologists and is poised to replace mediastinoscopy in the future. For thoracic surgeons, the technique can be easily learned and it may be important to do so if our specialty is to maintain its traditional and important role in the diagnosis and staging of thoracic malignancies.
The EBUS bronchoscope (BF-UC160F-OL8; Olympus America Inc., Center Valley, PA) is similar in dimensions to a standard adult fiber optic bronchoscope. The 6 mm diameter scope has a curvilinear ultrasound (US) probe at its distal end which provides a 50 degrees linear continuous B-mode ultrasound image, with color Doppler capability to aid identification of vascular structures . Proximal to the US probe, and at 30 degrees to the long axis of the bronchoscope, are a fiber optic lens and a biopsy channel, through which a 22-G biopsy needle can be passed (NA-201SX-4022; Olympus America Inc., Center Valley, PA) . A disposable latex balloon is placed over the US probe, which is inflated with sterile water to provide a fluid interface between the probe and the tracheal wall.
Operative Steps
The biopsy needle consists of a 22-guage needle with inner stylet housed in a flexible sheath, both of which may move independently of one another relative to the bronchoscope. The biopsy needle is passed through the biopsy channel and the housing secured to the bronchoscope by a flange. There are two main techniques to perform transbronchial puncture. The ‘quick jab’ technique is easiest and most useful for the subcarinal nodes or nodes along the main stem bronchi where the cartilage is thinner (Figures 8 and 9). With the node visualized by US, the sheath is advanced out of the end of the scope until the top right corner of the ultrasound image becomes slightly indented. This indicates that the end of the sheath is in contact with the wall of the bronchus and it is therefore safe to advance the needle. The guard for the needle is then released and using a quick jab the needle is plunged into the lymph node. If the needle is more slowly advanced there is a tendency for it to push the wall of the bronchus away from the scope, thus losing contact with the balloon and resulting in image loss. Once the needle is visualized within the lymph node, the stylet is moved in an out a few times to dislodge any bronchial epithelium that may have entered the needle, and then withdrawn. Suction is applied to the biopsy needle (typically negative 20 cc of air using a Vac-Loc syringe) and the needle passed in and out of the node approximately 10 times under US visualization. Suction is then released and the entire biopsy needle withdrawn. Smears are prepared by advancing the needle out of the sheath, reinserting the stylet and applying a drop of the aspirate to frosted glass slides. Air is used to ‘flush’ remaining aspirate material either onto additional slides or into RPMI medium for cell block analysis.
Specificity is as high as
90%.
EBUS being performed under general intravenous anesthesia with use of laryngeal mask airway. The CV-180 video processor enables picture-in-picture display, which allows easy correlation between visualized anatomy and the ultrasonic image.
Reference:
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