You may need to undress and put on a hospital gown. You will need to take out any false teeth or contact lenses.

You may be given an injection of antibiotics to help prevent an infection later. Your throat will be numbed with a spray, or with a lozenge that you suck. This means you won’t feel any pain as the endoscope goes in.

You don’t need to be put to sleep, but your doctor may offer you a mild sedative injection. It will make you feel drowsy, relaxed and less anxious.

To have the test you lie on a table. A fine, soft tube is placed into one nostril to give you a little oxygen to breathe. Your pulse and oxygen levels are checked throughout.

When you are ready, the doctor or nurse passes the endoscope over the tongue, down through the gullet and into the stomach and the first part of the bowel. The endoscope is about the thickness of your little finger.

This won’t hurt, but it may feel uncomfortable. Don’t worry – you aren’t going to choke. The feeling will pass, and once the tube is in place, the worst is over.

A liquid called contrast medium is then injected through the endoscope. This lets the doctor see your pancreas and bile duct more easily on the X-rays. Afterwards the liquid passes harmlessly out of the body.

As well as looking at your body organs the doctor may take some samples of tissue (biopsies) to be looked at later under a microscope.

The procedure normally takes about 30 minutes. Then the endoscope is gently removed.