A 28-year-old man presents to the emergency department with acute onset proptosis, chemosis, ophthalmoplegia, and fever (38.5°C) for 2 days. He reports a history of sinusitis 1 week ago. On examination, visual acuity is 6/9 in both eyes, intraocular pressure is elevated, and fundoscopy shows disc edema. CT orbit with contrast shows inflammatory changes in the orbital fat with no discrete abscess. Blood cultures have been drawn. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis This patient presents with the classic pentad of orbital cellulitis: proptosis, chemosis, ophthalmoplegia, fever, and vision impairment. The CT finding of inflammatory orbital fat without a localized abscess confirms diffuse orbital cellulitis rather than orbital abscess. ## Management Algorithm ```mermaid flowchart TD A["Orbital Cellulitis Suspected"]:::outcome --> B{"Imaging shows abscess?"}:::decision B -->|Yes| C["Surgical drainage + IV antibiotics"]:::action B -->|No| D["Diffuse cellulitis"]:::outcome D --> E["Blood cultures drawn?"]:::decision E -->|Yes| F["Start broad-spectrum IV antibiotics immediately"]:::action E -->|No| G["Draw cultures, then start antibiotics"]:::action F --> H["Adjunctive: corticosteroids, treat sinusitis"]:::action G --> H H --> I["Daily clinical reassessment"]:::action I --> J{"Improvement in 48-72 hrs?"}:::decision J -->|Yes| K["Continue IV antibiotics 2-3 weeks"]:::outcome J -->|No| L["Repeat imaging, consider drainage"]:::urgent ``` ## Rationale for Correct Answer **Key Point:** Orbital cellulitis is a medical emergency requiring empiric broad-spectrum IV antibiotics initiated immediately after blood cultures are obtained — not delayed by further investigation. **High-Yield:** The antibiotic regimen must cover: - *Staphylococcus aureus* (including MRSA in some regions) - *Streptococcus pneumoniae* - Gram-negative organisms (*Haemophilus influenzae*, *Klebsiella*) - Anaerobes (if odontogenic or sinusitis source) **Standard empiric regimen:** - **Ceftriaxone** 2 g IV 12-hourly (broad Gram-negative + Gram-positive coverage) - **Vancomycin** 15–20 mg/kg IV 8–12-hourly (MRSA coverage) - **Metronidazole** 500 mg IV 8-hourly (anaerobic coverage) **Clinical Pearl:** Blood cultures should be drawn before antibiotics, but antibiotic administration must NOT be delayed waiting for culture results. The risk of vision loss and cavernous sinus thrombosis is too high. ## Why Observation Is Dangerous Orbital cellulitis can progress to: - Cavernous sinus thrombosis (mortality 5–10% even with treatment) - Optic nerve ischemia and permanent vision loss - Meningitis Every hour of delay increases morbidity. Topical antibiotics and NSAIDs alone are insufficient. ## Role of Imaging & Surgery - **CT/MRI:** Repeat if no clinical improvement by 48–72 hours to rule out abscess formation requiring drainage. - **Surgery:** Reserved for localized abscess, failure to respond to antibiotics, or signs of vision-threatening complications. [cite:Harrison 21e Ch 379]