History: 45 year old female with congestion and headache.

This is the appearance of acute sinusitis on CT. Sinusitis is inflammation of the sinuses as a result of infection with a virus, bacteria, or fungus. Usually patients do not need imaging for diagnosing sinusitis as it is diagnosed clinically by history and physical exam. However, sinusitis is frequently an incidental finding on head and maxillofacial imaging studies. On CT, features that suggest acute versus chronic sinusitis include air fluid levels and bubbly secretions, with a lack of underlying bony changes. Chronic sinusitis is diagnosed in the presence of underlying sclerosis of the bony walls of the sinuses.

The differential for this appearance includes a “pseudo” fluid level (a mucus retention cyst), a blood level in the setting of trauma, and postobstructive secretions. If chronic sinusitis is considered, the differential diagnosis includes fungal sinusitis, fungal mycetoma, Wegner’s granulomatosis, sarcoidosis, and sinonasal polyposis.

Patients with cystic fibrosis and immotile cilia syndrome (Kartagener syndrome) are predisposed to sinusitis.