Whilst under anaesthetic, a long, thin flexible instrument is inserted through your mouth. The doctor will be able to look for any abnormalities which may be present. If necessary, small tissue samples (biopsies) can be taken during the examination (painlessly) for detailed laboratory analysis.

Some treatments can also be done through the endoscope. These include stretching (dilating) narrowed areas of the oesophagus, stomach or duodenum, removing polyps and swallowed objects, and treatment of bleeding blood vessels and ulcers by internal injection or application of heat (using electrical diathermy).