Endoscopic ultrasound (EUS) is a procedure combining the range of endoscopy with the diagnostic abilities of ultrasound. EUS is used in the imaging of the upper GI tract and surrounding structures as well as the respiratory tract (where it is referred to as endobronchial ultrasound, EBUS). A high frequency transducer crystal is used, typically in the range of 12-20 Megahertz.
In a healthy patient, five layers are seen1:
- innermost layer (hyperechoic): superficial mucosal layer corresponding to the interface of the oesophageal lumen and the mucosal layer
- second layer (hypoechoic): mucosal layer
- third layer (hyperechoic): submucosal layer
- fourth layer (hypoechoic): muscularis propria
- fifth layer (hyperechoic): esophageal adventitia
Endoscopic ultrasound can be used for local TNM staging of oesophageal cancer to determine the local invasion of the tumour through the normal oesophagus.
Endoscopic ultrasound can be used for aspiration of both solid and cystic pancreatic masses.