Acute Bacterial Rhinosinusitis (ABRS)

Risk factors

• Preceding viral URI (vast majority)
• Allergic rhinitis
• Anatomic obstruction (deviated septum, polyps, concha bullosa)
• Dental infection (maxillary sinus floor adjacent to molar roots)
• Smoking, air pollutants
• Immunodeficiency (HIV, hypogammaglobulinemia)
• Cystic fibrosis, primary ciliary dyskinesia
• Diabetes (mucormycosis risk)

Pathophysiology

Viral URI → mucosal edema and ciliary dysfunction obstruct sinus ostia → impaired mucociliary clearance and stagnant secretions → bacterial overgrowth. Dominant pathogens: Streptococcus pneumoniae, non-typeable Haemophilus influenzae, Moraxella catarrhalis. Staphylococcus aureus and anaerobes in chronic/severe cases. Odontogenic etiology → mixed oral flora.

Clinical presentation

Differential diagnosis

• Viral rhinosinusitis — Symptoms <10 days, peak at days 3-6 then improve; supportive care; antibiotics not indicated
• Allergic rhinitis with sinus congestion — Itch, sneezing, clear discharge, atopic history, no fever or facial pain; intranasal corticosteroid
• Chronic rhinosinusitis — Symptoms ≥12 weeks; nasal endoscopy shows polyps or purulence; CT confirms mucosal disease
• Dental abscess — Maxillary tooth pain with percussion, periapical lucency on dental imaging; treat underlying tooth
• Migraine or tension headache — Recurrent headache with photophobia/phonophobia or scalp tension; no purulent discharge or fever
• Invasive fungal sinusitis (mucormycosis) — Immunocompromised or poorly controlled diabetic with rapid facial pain, black eschar on turbinate or palate, cranial neuropathies; emergent ENT/surgical debridement + IV amphotericin B
• Nasal foreign body — Unilateral purulent foul discharge in a child
• Trigeminal neuralgia — Lancinating facial pain triggered by light touch; no purulent discharge

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[URI / sinus symptoms] --> B{Symptom duration<br/>and pattern}
  B -->|<10 days, improving| C[Viral rhinosinusitis<br/>Supportive care]
  B -->|≥10 days no improvement| D[ABRS]
  B -->|Severe onset ≥3-4 d<br/>T≥39 + purulent| D
  B -->|Double-sickening<br/>worse after improvement| D
  D --> E{Adult<br/>uncomplicated?}
  E -->|Yes| F[Option:<br/>watchful waiting 7 d<br/>OR amox-clav]
  E -->|No / risk factors| G[High-dose amox-clav<br/>5-10 days]
  F --> H{Improved?}
  G --> H
  H -->|Yes| I[Complete course]
  H -->|No at 72 h| J[Switch antibiotic<br/>± CT sinus<br/>± ENT referral]
  D --> K{Red flags?<br/>Orbital/intracranial/<br/>immunocompromised}
  K -->|Yes| L[Urgent CT/MRI<br/>IV antibiotics<br/>ENT/Ophtho]

Treatment

Complications

• Orbital cellulitis or abscess (especially ethmoid sinusitis in children) — proptosis, ophthalmoplegia, vision loss
• Subperiosteal abscess
• Cavernous sinus thrombosis — bilateral CN III/IV/VI palsies, proptosis, fever, altered mental status
• Pott puffy tumor — frontal sinusitis with osteomyelitis and forehead subperiosteal abscess
• Meningitis, epidural/subdural empyema, brain abscess
• Invasive fungal sinusitis in immunocompromised — mucormycosis, aspergillosis
• Progression to chronic rhinosinusitis

PANCE pearls

• Distinguishing viral from bacterial sinusitis: duration ≥10 days, double-sickening, or severe high-fever onset with purulent discharge ≥3-4 days.
• IDSA 2012 recommends amoxicillin-clavulanate over amoxicillin alone — most boards updated to this answer.
• Avoid macrolides and TMP-SMX as monotherapy — >25% pneumococcal resistance.
• Periorbital swelling + decreased EOM + proptosis = orbital cellulitis → IV antibiotics + CT + ophthalmology/ENT.
• Black necrotic eschar on palate or turbinates in a diabetic or immunocompromised patient = mucormycosis — emergent surgical debridement and IV amphotericin B.
• Intranasal corticosteroids improve symptoms in ABRS as adjunct therapy.

References

• IDSA 2012 — Chow AW et al. IDSA Clinical Practice Guideline for Acute Bacterial Rhinosinusitis. Clin Infect Dis 2012;54(8):e72-e112
• AAO-HNS 2015 — Rosenfeld RM et al. Clinical Practice Guideline (Update): Adult Sinusitis. Otolaryngol Head Neck Surg 2015;152(2S):S1-S39
• AAP 2013 — Wald ER et al. Clinical Practice Guideline for the Diagnosis and Management of Acute Bacterial Sinusitis in Children Aged 1 to 18 Years. Pediatrics 2013