Computed tomographic patterns of orbital cellulitis due to sinusitis

Purpose: To describe the CT findings of orbital cellulitis due to sinusitis. Methods: The records and CT scans of 45 consecutive patients with orbital cellulitis due to sinusitis treated at the Hospital of the Medical School of Ribeirão Preto were analyzed by a radiologist and two orbital surgeons. Results: Three major types of CT changes were observed: diffuse fat infiltration, subperiosteal abscess and orbital abscess. Diffuse fat infiltration (characterized by an increased density of the extra- or intraconal fat) was seen in 11 patients (24.44%). A subperiosteal abscess was diagnosed in 28 patients (62.23%). A surgically proved orbital abscess was detected in 6 patients (13.33%). Conclusions: In all cases of orbital cellulitis due to sinusitis intraorbital changes can be detected by CT scans either as a diffuse infiltration of the orbital fat or as a detachment of the periorbita (subperiosteal abscess) or a true orbital abscess. Category I of Chandler orbital cellulitis classification (inflammatory edema) must be understood as a stage of a process that is already happening within the orbit and, as the term "preseptal cellulitis" means a palpebral infection, this designation should not be used to stage orbital cellulitis.