For endoscopic ultrasound of the upper digestive tract, a probe is inserted into the esophagus, stomach, and duodenum during a procedure called esophagogastroduodenoscopy. Among other uses, it allows for screening for pancreatic cancer, esophageal cancer, and gastric cancer, as well as benign tumors of the upper gastrointestinal tract. It also allows for characterization and biopsy of any focal lesions found in the upper gastrointestinal tract, such as esophageal tuberculosis. This is done by inserting a needle through the stomach lining into the target. Less commonly this procedure is used to identify malformations and masses in the bile ducts and pancreatic ducts.