Putting a stent in by endoscopy. After you have had a sedative injection, the doctor puts a tube called an endoscope into your mouth and passes it down your throat to your stomach. The tube passes through to the beginning of the small bowel (your duodenum) and the opening of your bile duct.utting a stent in by endoscopy. After you have had a sedative injection, the doctor puts a tube called an endoscope into your mouth and passes it down your throat to your stomach. The tube passes through to the beginning of the small bowel (your duodenum) and the opening of your bile duct.