Axial CT post contrast Coronal CT bone windows

Diagnosis: Antral choanal polyp

Choanal polyps are usually antral choanal and arise from the maxillary antrum and protrude through the middle meatus extending into the nasal cavity to the back of the choana which is the boundary between the nasal cavity and the nasopharynx . A rare type of choanal polyp is a sphenochoanal polyp which arises from the sphenoid sinus and extends through the sphenoid ostium into the choana via the sphenoethmoidal recess. Many believe that the antral choanal polyp is simply a large mucous retention cyst within the maxillary sinus which has protruded into the nasopharynx. Antral choanal polyps represent approximately 5% of all nasal polyps and are more common in the pediatric population. Nasal polyps in general are associated with diabetes, vasomotor rhinitis, cystic fibrosis, and allergy. Nickel workers have been reported to have a high incidence of nasal polyps. On imaging, nasal polyps have a lower attenuation, 10-18 Hounsfield units similar to mucus and there may be calcification. On MR, the signal is a function of the amount of inspissated secretions; however, they are usually isointense on T1 and bright on T2 without enhancement except at the mucosal surface.

Nasal polyps are usually not a diagnostic dilemma on imaging. Other entities to consider in the differential of a low attenuation, non-enhancing, non-invasive nasopharyngeal mass may include nasal dermoid or epidermoid and cephalocele. Possibilities in the general differential of a nasopharyngeal mass include inverting papilloma, nasal angiofibroma, nasopharyngeal carcinoma, lymphoma, and esthesioneuroblastoma Related Cases

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Nasal angiofibroma Esthesioneuroblastoma Inverting papilloma