A stent is a tubular support placed inside a blood vessel, canal, or duct to either aid in healing or to relieve an obstruction or narrowing that has occurred in a structure. A stent is sometimes placed to treat collapsed trachea which is often seen in small dogs and restricts breathing. Fluoroscopy is used to guide to placement of a stent because this modality enables veterinarians to see structures in motion, such as food moving through the esophagus and urine flowing through the ureters. Subtle changes in the position of structures may be examined during movement such as the head, neck and joints of the limbs.