Chronic sinusitis is one of the more prevalent chronic illnesses in the United States, affecting persons of all age groups (see Epidemiology). It is an inflammatory process that involves the paranasal sinuses and persists for 12 weeks or longer (see Pathophysiology). The literature has supported that chronic sinusitis is almost always accompanied by concurrent nasal airway inflammation and is often preceded by rhinitis symptoms; thus, the term chronic rhinosinusitis (CRS) has evolved to more accurately describe this condition.