## **Core Concept**
The patient's presentation suggests a complication of sinusitis, given the history of purulent nasal discharge, fever, and opacification of the ethmoid sinus on X-ray, now presenting with conjunctival congestion and edema. This condition is concerning for orbital involvement, likely orbital cellulitis or abscess, which are known complications of ethmoid sinusitis due to the close proximity of the ethmoid sinuses to the orbit.

## **Why the Correct Answer is Right**
The correct approach in evaluating this patient would involve imaging to assess the extent of orbital involvement and potential complications. A CT scan of the orbits with contrast is the most appropriate next step. This is because CT scans can help differentiate between orbital cellulitis and an orbital abscess, both of which are complications of sinusitis. This differentiation is crucial for management, as an abscess may require surgical drainage.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While a detailed history and physical examination are crucial, they have already been performed, and the question asks for the next step in evaluating the patient given the current clinical picture and imaging findings.
- **Option B:** Starting antibiotics is important but does not address the need to evaluate the extent of the current orbital involvement. Antibiotics would likely be part of the treatment regimen but do not replace the need for imaging to guide further management.
- **Option C:** An MRI might provide detailed images of soft tissues but is not the first choice for evaluating acute orbital complications of sinusitis, especially when a quicker, more readily available test like CT can provide critical information on the need for surgical intervention.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ethmoid sinuses are most commonly involved in sinusitis complications leading to orbital cellulitis or abscess in children. The thin bony lamina between the ethmoid sinuses and the orbit makes it a vulnerable area for spread of infection.

## **Correct Answer:** . CT scan of orbits with contrast.