EUS combines ultrasound technology with endoscopy to gain an internal vantage point to obtain higher resolution ultrasound images. While conventional endoscopy only provides a view of the innermost lining of the digestive tract, or its wall, the addition of ultrasound allows the physician to see beyond that wall to visualize all five layers of the GI tract as well as surrounding tissue and organs.  EUS also provides a minimally invasive means for biopsy.