Dr. Mauricio González
MULTIMEDICA VISTA HERMOSA
The Endobronchial Ultrasound with Transbronchial Needle Aspiration procedure (EBUS–TBNA) is a new technology that allows sampling of the lung periphery as well as of the mediastinum and pulmonary hilum in a less invasive manner. There are two types of endobronchial ultrasound (EBUS) used in clinical practice: radial to locate peripheral pulmonary lesion andlineal to take specimens of hilar, and mediastinal lymph nodes and masses. Both ultrasounds are done under general anesthesia with access of the airway via an endotrachial tube or laryngeal mask.
RADIAL ENDOBRONCHIAL ULTRASOUND
The radial ultrasound was the first to be introduced, used initially by clinicians to detect the degree of invasion of malignant tumors of the bronchial wall in adults, and later adapted to investigate peripheral lung lesions. To perform the procedure, a flexible bronchoscope is used, a radial transducer of 1.2 mm. in diameter of 20 MHz (UM-S20-17S, Olympus, Tokyo, Japan) placed inside a plastic guide of 1.7 mm in diameter is passed through the work channel of the bronchoscope and is guided to the location suggested by means of the thoracic tomography, when the tissue lesion is found, the guide is left in the place in mention, the transducer is removed and the forceps or the cytology brush is introduced to take specimens. Hemorrhage or bleeding is rare probably because of the tamponade effect made by the plastic guide. Pneumothorax rates are reported in less than 0.5% of the cases compared to 20-40% reported in Percutaneous Lung Biopsy.
Diagnostic efficiency of the flexible bronchoscopy in the investigation of peripheral pulmonary lesions in adults is less than 20%. Diagnostic efficiency of the endobronchial ultrasound in the same investigation is above 80% in some reports. The majority of studies performed in adults with the endobronchial ultrasound are related to lung tumors, however, it has also been applied in patients with focal pulmonary lesions, as is the case of immunosuppression (with non/diagnostic routine bronchoscopies), tuberculosis, cryptococcosis, lung abscess, idiopathic interstitial pneumonia.
A great variety of diseases in children are presented with peripheral lung nodes that require histologic diagnosis as is the case of infectious or inflammatory processes including granulomas, fungal infections, primary embolus and post-transplant secondary tumors. Previously, surgery was needed to take a biopsy in these patients. Thoracoscopy is associated with significant morbidity; up to 13% of cases become an open thoracotomy. The Percutaneous Pulmonary Biopsy can also be performed but with complications in up to 44% of the cases. Pneumothorax can occur in up to 17% of the cases after a TAC guided thoracic biopsy and bleeding has been reported in 13 to 46% of the cases. The endobronchial ultrasound in the context of older children (12 years old) can provide a safe alternative to open lung biopsy or to percutaneous radiologic techniques.
To be able to use a transducer of 1.2 mm., a bronchoscope of 4.9 mm in diameter with a work channel of 2 mm. is required. The endotrachial tube must be number 6 and in case of a laryngeal mask 2.5 which allows appropriate ventilation of the patient with such a bronchoscope. These devices can be used in a child as young as 8 years old, but it is not until approximately the 12th year of age when they can be used to detect peripheral lesions.
A concern regarding the use of endobronchial ultrasound in the pediatric population is the degree of radiation exposure, since the procedure is performed using fluoroscopy. The optimum procedure is performed under fluoroscopy because it minimizes the probability of Pneumothorax, it ensures that the plastic guide is properly placed and that the sampling instruments keep a prudent distance from lung periphery.
LINEAL ENDOBRONCHIAL ULTRASOUND
It was initially developed to delimit lung cancer stages by less invasive means. It is performed with a specific Bronchoscope (BF-UC160F-OL8, Olympus) with a transducer mounted in the end of the bronchoscope. The bronchoscope has a maximum external diameter of 6.9 mm, characteristic unique optics, with a 30 degree oblique camera. The transducer has a range of vision of 130 degrees, with images taken at 90 degrees of the bronchoscope. The Doppler mode can be used to confirm the presence of blood fluid on suspicion of vascular structures. The images produced by the ultrasound are processed by a specific Scanner (EU-C60, Olympus).
A ball is fastened on one end of the transducer and is filled with saline solution to allow adequate transmission of the ultrasound signal through the bronchial wall. Biopsies are performed using a specific No. 22 needle inserted through the work channel of the bronchoscope. The lineal endobronchial ultrasound has great diagnostic precision in mediastinal or hilar sampling and allows the patient to avoid more invasive diagnostic procedures. Its diagnostic efficiency is equivalent to mediastinoscopy for sampling lymph nodes of the upper mediastinal region, but is greater for sub-carinal lesions. Other advantages are its ability to access the hilar and posterior mediastinal regions, as its low number of complications and cost.
In literature there are no reports of significant complications to this date and in the centers where the lineal Ultrasound is practiced, it has substituted mediastinoscopy as the procedure of choice. The transducer has a diameter of 6.9 mm and can safely go through an endotrachial tube 7.5 but probably will need a number 8 to allow appropriate lung ventilation during the procedure.
These devices are not likely to be used in children under 12 years of age. The lineal ultrasound can be used in mediastinal masses more frequently in children: Lymphoma and Neuroblastoma, it also allows visualization of bronchogenic and enteric cysts, as well as the aspiration of the content of the cysts for diagnostic or therapeutic purposes. Other cases in which the lineal ultrasound can be of much help are hilar, sub-carinal and mediastinal adenopathy associated to Mycobacterium Tuberculosis and Mycobacteria not tuberculosis, as well as Sarcoidosis and other granulomatous diseases.
The indications to perform endobronchial ultrasounds (EBUS) may differ significantly between the adult and the pediatric populations, but the advantages of the technique continue to be the same: It is a less invasive technique that allows sampling of peripheral lung lesions, mediastinal or hilar masses with a great diagnostic precision and a significantly less morbi-mortality.