Endoscopic examination now available for more than 3-4 decades, has made it possible to visualize the organs such as the stomach, the colon and other parts of the intestine, genitor-urinary system and the tracheobronchial tree in the lungs. The laparoscopic and thoracoscopic examinations of the peritoneal and the pleural cavities involve small incisions and a minimal surgical approach to look into the close cavities which could not be otherwise examined. Their examination has also allowed to take biopsy and fluid specimens for histo-pathological, cytological, microbiological, biochemical and immunological investigations for diagnosis of different diseases. There however remain some areas particularly in the chest which can not be seen and examined with ease. Mediastinum, the area between the two lungs which contains the heart, the great vessels and several other structures is one such area which is largely unapproachable.
Mediastinum in particular, contains the lymph nodes which are commonly involved in diseases such as tuberculosis, cancers (e.g. lymphomas and metastases), sarcoidosis and other lymphomatous disorders. Mediastinoscopy is sometimes employed to get lymph node biopsy and other specimens from the mediastinum. This is however fraught with complications which are generally considered of greater magnitude than the benefits obtained from this procedure. Moreover, the investigation involves expertise of a thoracic surgeon which is generally unavailable.
In the last few years, a new technique i.e. endobronchial ultrasound (EBUS) has become available which accurately guides the endoscopist to obtain aspirates from lymph nodes and other masses/ tumours in the vicinity. The EBUS guided aspiration is highly safe and accurate in the diagnosis of diseases such as cancers, sarcoidosis and tuberculosis (etc.). It has been extensively used to stage lung cancer to decide the form of therapy – surgical or non-surgical (radio and/or chemotherapy).
For the present, the EBUS guided aspiration is a relatively costlier test because of the costs of the set-up required for the procedure, the equipment and the needle used for aspiration. Moreover, it requires enough experience and training to get good results. The EBUS guided needle aspiration along with other bronchoscopic biopsies have been proven to be most successful for the diagnosis of sarcoidosis, which is being now commonly seen. It has significantly improved the success rates of the investigations. One expects that the cost will come down after the cheaper needles become available.