Choanal Atresia
Basic Information 
Clinical Presentation
History, Chief Complaint
• Foals affected with bilateral choanal atresia are unable to breathe at birth and present with acute respiratory distress. Foals with bilateral choanal atresia usually die unless an emergency tracheotomy or orotracheal intubation is performed. Placement of the hands over the nares reveals no air movement from the nares.
• Unilateral choanal atresia may not be clinically evident until the horse is placed into athletic training. Affected horses make a respiratory noise and develop exercise intolerance. An additional abnormality is failure to pass a nasogastric tube on the affected side(s).
Physical Exam Findings
• The diagnosis of choanal atresia is suspected based on clinical signs of nasal obstruction or severe dyspnea in foals at birth. Evaluation of airflow from the nares reveals no air movement from the affected side(s).
• Endoscopy is the best method to confirm choanal atresia. Endoscopic findings compatible with choanal atresia include failure to pass the endoscope into the nasopharynx and the presence of a sheet of tissue at the caudal aspect of the junction between the ethmoid turbinates, nasal septum, and caudal nasal conchae. Because of the obstructing membrane, the nasopharynx cannot be visualized.
Etiology and Pathophysiology
• Choanal atresia results from failure of the bucconasal membrane to separate from the primitive buccal or oral cavity from the nasal pits during embryologic development.
• This membrane can be complete, consisting of bone or fibrocartilage, or membranous. In horses, the majority of affected cases are membranous.
• Bilateral choanal atresia results in dyspnea at birth and may result in death if an emergency tracheotomy is not performed.
• Unilateral choanal atresia is typically not diagnosed until the horse is placed into training and is not life threatening.
Diagnosis 
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
