Gastrointestinal (GI) endoscopies are performed using one of two techniques: inserting the endoscope through the mouth to examine the upper GI tract, or inserting the endoscope through the anus to examine the lower GI tract.  

When the endoscope is inserted through the mouth, it is known as an upper endoscopy. This approach enables the physician to view the esophagus, stomach and duodenum. Also known as an esophagogastroduodenoscopy, this procedure is used to diagnose swallowing difficulties, nausea and vomiting, reflux, bleeding, indigestion, abdominal pain, and chest pain. These procedures normally take between 15 to 20 minutes. Examples of upper endoscopies include:

• Esophagoscopy. Examines the esophagus.
  
  
• Gastroscopy. Examines the stomach.
  
  
• Upper GI endoscopy. Examines the esophagus, stomach and duodenum (the first part of the small intestine).
  

  

• Enteroscopy. The small intestine beyond the duodenum is examined using a long endoscope, or enteroscope.
  
  
• Endoscopic retrograde cholangiopancreatography (ERCP). An examination of gallbladder, pancreas, and the ducts that drain into the liver. After the endoscope is inserted, a dye is passed through a thin flexible tube (catheter) inside the endoscope before x-rays are taken.

In other cases, the endoscope is inserted through the anus. This allows the physician to see the anus, rectum and large intestine. It may take from a few minutes to an hour to perform these procedures. There are three major types of these endoscopies:

• Anoscopy. Examines the anus.
  
  
• Sigmoidoscopy. Examines the lower part of the large intestine (sigmoid colon), the rectum and the anus.
  
  
• Colonoscopy. Examines the entire large intestine, the rectum and the anus.