Anomalous tracheal cartilage Complete tracheal ring 2021-09-30T16:02:28Z Continuous or nearly continuous configuration of the cartilaginous tracheal ring. Complete tracheal rings Complete tracheal ring deformity The trachea is surrounded by 16-20 rings of hyaline cartilage; these rings are incomplete and horseshoe-shaped (C-shaped). In complete tracheal rings, the rings encircle the entire trachea (O-shaped) or nearly the entire trachea. Pulmonary artery sling is a vascular anomaly often seen in CTRD in which the left pulmonary artery (LPA) originates from the right pulmonary artery (RPA) and encircles the distal trachea and right primary bronchus before entering the hilum of the left lung. Pumonary artery sling should be coded separately (HP:0004961). CTRD