Diagnostic imaging in 2009: update on evidence-based practice of pediatric imaging. What is the role of imaging in sinusitis?

Abstract

Acute sinusitis is bacterial infection of the paranasal sinuses. Under normal circumstance, the paranasal sinuses are assumed to be sterile. However, the paranasal sinuses are continuous to nasal mucosa or nasopharynx that are heavily colonized with bacteria. These bacteria are present in low density and removed by the normal mucociliary function of the paranasal sinuses. Normal mucous secretions contain antibodies, and together with mucociliary clearance, work to clear bacterial from the paranasal sinuses. Thus, maintaining the mucociliary flow and an intact local mucosal surface are key host defenses against infection [1]. The common predisposing events that set the stage for acute bacterial sinusitis are an acute viral upper respiratory infection that results in a viral rhinosinusitis (predisposes to approximately 80% of bacterial sinus infections), and allergic inflammation (that predisposes to 20% of bacterial infection). Once the mucosa of the paranasal sinuses swells due to either viral infection or allergy, it causes sinus ostia obstruction, thus interfere with the normal mucociliary clearance. This leads to low pressure within the paranasal sinuses thus further exaggerate mucosal thickening and poor sinus clearance, resulting in acute bacterial sinus infection. Streptococcus pneumonia and Hemophilus influenza are two common organisms for acute bacterial sinusitis. Since the widespread use of the heptavalent pneumococcal conjugate vaccine (PCV7) in 2004, pneumococcal strains have declined thus, H influenza has become a more prevalent organism [2, 3]. Other organisms include Moraxella catarrhalis, other Streptococcus species, and Staphylococcus.