A gastroscopy often takes less than 15 minutes, although it may take longer if it's being used to treat a condition. It's usually carried out as an outpatient procedure, which means you won't have to spend the night in hospital.Before the procedure, your throat will be numbed with a local anaesthetic spray. gastroscopy is a procedure where a thin, flexible tube called an end oscope is used to look inside the oesophagus (gullet), stomach and first part of the small intestine (duodenum). It's also sometimes referred to as an upper gastrointestinal endoscopy. The endoscope has a light and a camera at one end.