Opaque maxillary antrum: a pictorial review.

The demonstration of an opaque antrum on a plain radiograph or cross-sectional imaging leads to consideration of an extensive differential diagnosis. Relevant clinical details narrow the differential and include the patient's age, signs and symptoms, a history of recent trauma, prior surgery or dental treatment. Computed tomography remains the most useful technique in coming to a specific diagnosis. Magnetic resonance imaging adds specificity in a few selected situations and is required in conjunction with CT in the staging of malignant tumours.