For endoscopic ultrasound (EUS), a high-frequency US transducer is incorporated into the tip of an endoscope to provide high-resolution images of the gastrointestinal wall and structures in close proximity to the gastrointestinal tract. Linear echoendoscopes that can image parallel to the long axis of the instrument allow visualisation of a projecting needle, relative to adjacent tissue, making EUS-guided aspiration or intervention possible. Transoesophageal EUS-guided real-time fine-needle aspiration (FNA) of mediastinal lymph nodes (particularly subaortic, subcarinal, paraoesophageal and pulmonary ligament nodes) has become a useful, minimally invasive and safe method for staging the mediastinum, to confirm or refute N2 or N3 disease in patients with nonsmall cell lung cancer. EUS-FNA has a pooled sensitivity and specificity of 84 and 99.5%, respectively, for the detection of malignant mediastinal lymph nodes in lung cancer.
Endobronchial ultrasound (EBUS) is another relatively new technique that allows ultrasound-guided sampling of mediastinal lymph nodes. EBUS-transbronchial needle aspiration (EBUS-TBNA) can be performed with real-time guidance using a bronchoscope with a convex ultrasound probe (Fig. 1). EBUS-TBNA is particularly useful for sampling high mediastinal, paratracheal, subcarinal, hilar and interlobar nodes, with a pooled sensitivity of 90% for mediastinal lymph node staging. Recently, Herth et al. evaluated a combined mediastinal staging approach using both EUS-FNA and EBUSTBNA performed by a single operator in a single sitting, and found a combined sensitivity of 96%, higher than that for either technique alone. Such combined minimally invasive approaches may find wider clinical applicability in appropriately selected lung cancer patients in the future.
FIGURE 1 ■ Endobronchial ultrasound-transbronchial aspiration (EBUS-TBNA) of a subcarinal node in a patient with mediastinal lymphadenopathy. The needle is visualised as a linear focus of high echoreflectivity (arrow). (Courtesy of Dr Pallav Shah, Royal Brompton Hospital.)
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