It is a test that lets the doctor look at the lining of your:

• oesophagus (gullet)
   

• stomach
   

• duodenum (the first part of the small intestine).

The test is done with a thin, flexible telescopic instrument called an endoscope. It is passed through the mouth and down into the stomach. The doctor can look for anything unusual, and take samples of tissue (biopsies) to be examined under a microscope.