Nowadays, the gastroscopy(esophageal gastro-duodenoscopy) is the most powerful method to recognize organic changes in the esophagus, stomach and duodenum.
What does the preparation look like?
The upper digestive tract must be completely empty for a conclusive assessment. The gastroscopy has to be done on an empty stomach. That means the last meal must be eaten at 10pm at the latest and the last drink consumed 6 hours prior. The medication must be consulted with the physician.
How is a gastroscopy performed?
Basically, the patient can decide to take a form of anesthetic (sedative syringe / anesthetic syringe / pharynx spray). This is recommended, as the muscles relax and a gag reflex will be suppressed.
The optical endoscope is then passed through the mouth via the esophagus into the stomach and duodenum. The stomach is inflated with air, in order to be able to assess the smallest changes of the mucous membrane.
Biopsies should be taken from different parts of the stomach in order to test for infestation with the Helicobacter pylori bacterium, but also to exclude an autoimmune gastritis(missing intrinsic factor). Sometimes, treatment procedures, e.g. Polyp removal or haemostasis. After the test has been completed, the air is sucked out again and the endoscope will be removed.
Immediately after the gastroscopy a feedback is received about possible optically recognisable reddening, if present. Only after histological evaluation an accurate diagnosis can be made.

What are the complications?
As with any examination, there are of course complications. However, the gastroscopy is a very low-risk routine procedure.
Very rarely it can lead to injuries of the stomach wall, risking perforation, stronger hemorrhage during tissue sampling, impairment of the respiratory function, hypersensitivity reactions or cardiovascular problems.
How does the treatment feel?
The treatment usually takes less than 10 minutes and if an anesthetic is taken, it is not at all unpleasant. Only after the examination a rough neck can be perceived.
There is also an after-effect of anesthesia. That is why at least one hour after, neither food should be eaten nor drinks drunk. Since there can be a little air in the stomach, outgoing winds are not abnormal. If the mucous membrane has been injured during treatment, it can lead to higher sensitivity to foods.
*This post is based on research and personal experience. All products (if any mentioned) are bought and tried by myself if not written otherwise.