Choanal atresia is caused by the bucconasal membrane, a membrane that separates portions of the mouth and nose during fetal development but is normally gone by birth. In choanal atresia, the membrane is still present at birth and one or both nostrils are partially or completely shut off from the rest of the respiratory system. Clinical signs are evident immediately after birth in foals in which both nostrils are affected, because labored breathing is severe and air cannot be detected passing through the nostrils. This is a life-threatening condition. Immediately after birth, a tube must be inserted through the neck into the trachea (tracheotomy) to allow the foal to breathe until the condition can be corrected. The situation is less severe if only one nostril is affected.

Last full review/revision July 2011 by Bonnie R. Rush, DVM, MS, DACVIM; Neil W. Dyer, DVM, MS, DACVP; Joe Hauptman, DVM, MS, DACVS; Ned F. Kuehn, DVM, MS, DACVIM; Stuart M. Taylor, PhD, BVMS, MRCVS, DECVP; Wendy E. Vaala, VMD, DACVIM; Maureen H. Milne, BVMS, MVM, DCHP, MRCVS