Endoscopic ultrasound (EUS) uses sound waves (ultrasound) to produce high quality images of the lining of the upper digestive tract (esophagus, stomach, and 1st part of the small intestine); as well other organs that are near it such as the liver, gallbladder, pancreas, and surrounding lymph nodes.
It can be combined with a procedure called fine needle aspiration (FNA) where a needle can be advanced from the probe to the target organs and a small sample aspirated through the needle. The sample can then be sent to the lab to be analyzed.
EUS can also be used to provide a minimally invasive way of draining pseudocysts from the pancreas. Pseudocysts are fluid-filled sacs that appear like a true cyst. However, the sac is not composed of a specific lining of cells that are common to a true cyst.