Guidelines for Differentiating Acute and Chronic Rhinosinusitis

1. Definition & Classification

Acute rhinosinusitis is defined by symptom duration of less than 4 weeks and is usually precipitated by an upper‑respiratory‑tract infection. 1
Chronic rhinosinusitis is defined by symptoms lasting 8 weeks or longer and requires abnormal CT or MRI findings for diagnosis. 1
Sub‑acute rhinosinusitis represents symptoms lasting 4–8 weeks, reflecting unresolved acute disease. 1
Recurrent acute rhinosinusitis is characterized by ≥ 3 episodes per year with complete resolution between attacks. 1

Both acute and chronic forms share the following symptoms: purulent rhinorrhea, post‑nasal drainage, nasal congestion, facial pain/pressure, headache, cough, and anosmia. 1
Acute bacterial rhinosinusitis more often presents with high‑grade fever (≥ 39 °C) and a sudden, severe onset, whereas chronic disease tends to have vague or insidious symptoms. 1

Acute rhinosinusitis is primarily an infectious process (viral or bacterial). 1
Chronic rhinosinusitis is principally an inflammatory disorder; the contribution of bacterial infection is uncertain. 1
Chronic disease can be subdivided into infectious and hyperplastic (non‑infectious) phenotypes. 1
Hyperplastic eosinophilic chronic rhinosinusitis is marked by eosinophil‑predominant inflammation and is frequently associated with nasal polyps, asthma, and aspirin sensitivity. 6

Diagnosis is clinical, based on symptom duration and presentation; imaging is not recommended for uncomplicated cases. 1
Imaging abnormalities are common in healthy individuals with viral URIs and therefore unreliable for acute diagnosis. 7
Acute bacterial rhinosinusitis should be diagnosed when symptoms persist ≥ 10 days without improvement or when there is “double worsening” (symptom worsening after initial improvement within 10 days). 8

CT or MRI imaging is required to confirm the diagnosis. 1
Operational definition: persistent inflammation documented on imaging at least 4 weeks after initiating appropriate medical therapy. 1
Up to 50 % of patients with a strong clinical history of chronic rhinosinusitis may have normal CT scans, underscoring diagnostic complexity. 1

First‑line therapy: amoxicillin ± clavulanate; treatment duration 10–14 days. 10
Watchful waiting is appropriate for mild, uncomplicated cases. 8

Antibiotics have a controversial and limited role; long‑term courses are generally not beneficial. 10
Intranasal corticosteroids are the mainstay of therapy. 10
Systemic corticosteroids may be considered for the hyperplastic eosinophilic phenotype. 1
Functional endoscopic sinus surgery is reserved for medically refractory disease. 1

Do not diagnose chronic rhinosinusitis on symptoms alone; imaging confirmation is essential. 1
Avoid assuming chronic disease is a persistent bacterial infection that requires prolonged antibiotics; it is fundamentally inflammatory. 1
The term “rhinosinusitis” is preferred over “sinusitis” because nasal cavity inflammation accompanies sinus involvement. 1