Endoscopic ultrasound
Overview
Endoscopic ultrasound is a medical procedure in which an endoscopically directed ultrasound is used to image thoracic and abdominal viscera.
A probe is inserted into the stomach and duodenum via esophagogastroduodenoscopy. Among other uses, it allows for screening for pancreatic cancer. It also allows for biopsing of any focal lesions found in the pancreas. This is done by inserting a needle through the stomach lining into the target.
Endoscopic ultrasound is performed with the patient sedated. The endoscope is passed through the mouth and advanced to the level of the duodenum. From various positions between the esophagus and duodenum organs outside the gastrointestinal tract can be imaged to see if they are abnormal and they can be biopsied by a process called "fine needle aspiration." Organs such as the liver, pancreas and adrenal glands are easily biopsied as are any abnormal lymph nodes. In addition the gastrointestinal wall itself can be imaged to see if it is abnormaly thick suggesting inflammation or malignancy. The quality of the image produced is directly proportional to the frequency used. Therefore a high frequency produces a better image. However, high frequency ultrasound does not penetrate as well as lower frequency ultrasound so that the examination of the nearby organs is not possible. The procedure is performed by gastroenterologists who have had extensive advanced training.