Swollen nasal mucosa (the lining of the nose) may be red, irritated, or inflamed. Pus-filled discharge may be present. Computed tomography (CT scan) or magnetic resonance imaging (MRI) may also show the sinuses filled with fluid or in an inflamed, swollen state. CT scan or MRI may be used to look for serious complications of sinusitis, such as involvement of the ocular (vision) system, meningitis, or encephalitis. Because sinusitis symptoms can be similar to those of other illnesses, in some cases it may be necessary to do tests to make certain there is not another cause of the symptoms.