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A 55-year-old woman reports sinus pressure for the past 2 weeks along with headache, rhinorrhea, postnasal drip, and cough that followed a cold 3 weeks ago. She has chronic allergic rhinitis, but now the pressure on the right side of her face has become intense and her right upper molars are painful. The nasal discharge has become discolored and she feels feverish. She is diagnosed clinically with right maxillary sinusitis and elects antibiotic treatment with amoxicillin. Two weeks later when her symptoms have persisted, a CT is ordered and she is found to have air-fluid levels in both maxillary sinuses and loculated fluid on the right side (Figures 33-1 and 33-2). The antibiotic is changed to amoxicillin/clavulanate and she is given information about nasal saline irrigation for symptom relief. If the symptoms don't improve, the clinician plans to send her to ear, nose, and throat (ENT) for further evaluation.


Bilateral maxillary sinusitis on axial CT. Note that fluid levels are greater on the right. (Reproduced with permission from Chris McMains, MD.)


Maxillary sinusitis on coronal CT of same patient. (Reproduced with permission from Chris McMains, MD.)


Rhinosinusitis is symptomatic inflammation of the paranasal sinuses, nasal cavity, and their epithelial lining.1 Mucosal edema blocks mucous drainage, creating a culture medium for viruses and bacteria. Rhinosinusitis is classified by duration as acute (<4 weeks), subacute (4 to 12 weeks), or chronic (>12 weeks).


  • Rhinosinusitis is common in the United States, with an age-adjusted prevalence of 11.7% of the adult population in 2015.2 The prevalence is increased in women and in individuals living in the southern United States.

  • Only 10% of adults with symptoms of sinusitis actually have bacterial infection; in contrast 60% of children with sinusitis have a bacterial cause.3 Of adult patients with acute viral sinusitis accompanying an upper respiratory tract infection (URI), only 0.5% to 2.5% develop superimposed acute bacterial sinusitis.4

  • The prevalence of chronic rhinosinusitis in patients referred for evaluation of potential chronic rhinosinusitis, based on symptoms, ranges from 65% to 80%.1

  • Children average 6 to 8 colds per year. In one study of 112 children with URIs, 8% developed sinusitis.5


  • Sinus cavities are lined with mucus-secreting respiratory epithelium. The mucus is transported by ciliary action through the sinus ostia (openings) to the nasal cavity. Under normal conditions, the paranasal sinuses are sterile cavities and there is no mucus retention.

  • Bacterial sinusitis occurs when ostia become obstructed or ciliary action is impaired, causing mucus accumulation and secondary bacterial overgrowth.

  • The causes of sinusitis include6:

    • Infection—Most commonly ...

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