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.