Lung Nodule Management

An Interventional Pulmonology Perspective

Udit Chaddha, MBBS; Jonathan S. Kurman, MD, MBA; Amit Mahajan, MD, FCCP; D. Kyle Hogarth, MD

Disclosures

Semin Respir Crit Care Med. 2018;39(6):661-666. 

In This Article

Radial Endobronchial Ultrasound

The r-EBUS employs a 20-MHz flexible catheter that houses a rotating ultrasound transducer that produces a real-time 360° ultrasound image of the airway wall and surrounding structures. When advanced into the lung periphery, the small diameter of the airways allows for perfect contact with the wall surface. The radial probe can be advanced through the biopsy channel of the bronchoscope either directly or through a guide sheath.[13] When a guide sheath is used, it improves access to smaller lesions by acting like an extended working channel (EWC), through which small instruments can be passed to the target area once the probe itself is removed. Alternatively, thin bronchoscopes can be used to navigate further into the periphery obviating the need for a guide sheath.[14] Fluoroscopic guidance can also be used as a supplement to the sonographic view.[15] The junction of the characteristic snowstorm appearance of the low-density alveolated normal lung and the solid tumor, represented by a hyperechoic line, allows the operator to guide the probe into the desired location.

The use of r-EBUS to visualize and guide biopsies of peripheral lung lesions was first described by Hürter and Hanrath in 1992.[16] Herth et al first prospectively studied r-EBUS, comparing it to fluoroscopy-guided transbronchial biopsies (TBBs).[17] While they did not achieve an overall improvement in diagnostic yield (80 vs. 76%), there was a nonsignificant trend for r-EBUS to better diagnose lesions <3 cm in size.

r-EBUS has since been studied to confirm its improved diagnostic yield compared to conventional TBB,[18] with an overall pneumothorax rate of approximately 1%. This represents a significant improvement compared to CT-guided lung biopsies.[19] The diagnostic yield, however, is lower for lesions smaller than 2 cm.[20] Chen et al clearly demonstrated an increase in yield with each centimeter increase in size of the peripheral lung lesion.[21] The yield was 84% when the probe was within the target (concentric sonographic view) as opposed to only 48% when the probe was adjacent to the lesion (eccentric view).

In 2013, an American College of Chest Physicians (ACCP) statement[22] quoted a 73% yield of r-EBUS for diagnosing peripheral lung cancers which led to the recommendation: "In patients suspected of having lung cancer, who have a peripheral lung nodule, and a tissue diagnosis is required due to uncertainty of diagnosis or poor surgical candidacy, r-EBUS is recommended as an adjunct imaging modality (Grade 1C)." While a very safe and feasible technology,[23,24] r-EBUS is far from a complete platform. It involves somewhat blind advancement of the catheter toward the target lesion using the operator's knowledge of airway anatomy and the available imaging (and sometimes fluoroscopy), and lacks a navigation platform to guide the catheter into the appropriate airway. Multimodality bronchoscopy, using EMN in combination with r-EBUS, results in a higher diagnostic yield.[10] In general, the yield is dependent upon a lesion's size, its distance from the hilum, and the sonographic view obtained. Ground glass nodules are not easily visualized with ultrasound. The previously reported high yield of r-EBUS was not confirmed by the AQuIRE registry, which is based on real-world data, that found an overall diagnostic yield of only 57%.[25] This finding was confirmed by a recent prospective, multicenter study.[26] The diagnostic yield remains inferior to the percutaneous approach.[19]

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