Total opacification of the maxillary sinus is a symptom of acute sinusitis which, according to MedScape, can be caused by an infection, structural variations in the nasal cavity, allergic responses or nasociliary malfunction. Sinonasal polyps are another condition that show up as opacified areas on a scan.
The maxillary sinuses are open cavities inside the maxilla, which is the upper jaw bone that extends upward on either side of the nose to the eye sockets. Normal sinus cavities show up as dark areas on CT scans and X-rays, while opacified areas show up as grey, and bone structures show up as white.
