Choanal atresia is most commonly due to-

Ans. is 'b' i.e., Presence of bucconasal membrane Choanal atresiao Choana, also called posterior nares, is an opening in the posterior part of each nasal cavity, through which nasal cavity communicates with nasopharynx.o Choanal atresia is a congenital anomaly characterized by closure of one or both posterior nasal cavities (i.e., choana). It is due to persistence of bucconasal membran.o Approximately 60- 70% of cases are unilateral and are more common on right side.o Bilateral cases occurs in 20-30% of patients and 50% of these patients are associated with other congenital anomaly, i.e., CHARGE syndrome - Coloboma, Heart defects, Choanal atresia, Retraded growth, Genitourinary abnormalities and Ear defects.Diagnosiso Unilateral lesions go unnoticed until the child presents with persistent unilateral nasal discharge. There is absence of air bubbles in nasal discharge. A simple test for unilateral choanal atresia is to have the child attempt nose blowing with opposite nostril occluded by external pressure. Failure to detect any air movement is suspicious for complete obstruction.o Bilateral choanal atresia presents as respiratory distress in newborn and requires support immediately after birth.o CT scan is the preferred imaging modality