A gastroscopy is a visual examination of your stomach. The examination is done through the mouth using a flexible telescope, called an endoscope, which is about as thick as a pencil. The endoscope lets the doctor see the inside of the gastrointestinal tract and any problems.
The examination is also called an upper gastrointestinal endoscopy, as it examines the upper gastrointestinal tract. You may also hear it called an upper GI endoscopy.