Endoscopic Ultrasound (EUS) combines endoscopy and ultrasound to obtain much more information than possible with the standard endoscopy. EUS uses a small ultrasound transducer that is installed on the tip of the endoscope to visualize the layers of the GI tract including esophagus, stomach and first portion of small bowl in addition to much of the organs in the upper GI tract including the liver, pancreas, left adrenal gland. Furthermore, much of the vascular and lymph nodes in the upper GI tract can also be visualized using EUS.

Given that the EUS transducer is placed at a very close proximity to the targeted organ(s), the images obtained are frequently more accurate and more detailed than the ones obtained by traditional ultrasound and depending on the clinical scenario and the organ targeted, more accurate and sensitive than more advanced imaging modalities such as CT scans. EUS is performed to evaluate abdominal pain, pancreatic masses/cysts, and chronic pancreatitis, detailed examination of the common bile duct and submucosal lesions, & staging of cancers of the digestive tract.

Other uses of EUS include studying the flow of blood inside blood vessels using Doppler ultrasound, and to obtain tissue samples by passing a special needle, under ultrasound guidance, into enlarged lymph nodes, and suspicious tumors. The process of obtaining tissue with a thin needle is called fine needle aspiration (FNA). EUS can also be used to perform celiac plexus block on patient suffering from chronic pancreatitis or neurolysis on patient suffering from pain associated with pancreatic cancer. EUS can also be used to drain cysts or abscess in the upper or lower GI tract.

Although complications can occur, they are rare when doctors with specialized training and experience perform the EUS examination. Potential but uncommon risks of EUS include bleeding at a biopsy site, reaction to the sedatives used, and aspiration of stomach contents into your lungs, infection, and complications from heart or lung diseases. Another very uncommon, but serous complication of EUS is perforation, which is a tear through the lining of the intestine that might require surgery to repair.  The possibility of complications increases slightly if a needle biopsy is performed during the EUS examination, including an increased risk of pancreatitis or infection. These risks must be balanced against the potential benefits of the procedure and the risks of alternative approaches to the condition.