CT differentiation of abscess and non-infected fluid in the postoperative neck

Background: Differentiation of postoperative neck abscess from non-infected fluid is important because the treatment is different. Purpose: To determine specific CT findings that might help to differentiate abscesses from non-infected fluid collections in the postoperative neck. Material and Methods: We retrospectively reviewed CT scans of 50 patients (43 men and 7 women; mean age, 62.5 +/- 8.9 years) who had postoperative fluid collections in the neck (26 abscesses and 24 non-infected fluid collections). Diagnosis of an abscess was determined by a positive bacteria culture from the fluid collection. Diagnoses were correlated with the following CT findings: anatomic spaces involved, the maximum transverse diameter, margin, attenuation, rim enhancement, gas bubbles, and manifestations of soft tissue adjacent to a fluid collection. Results: Rim enhancement pattern and soft tissue manifestations showed significant differences between abscess and non-infected fluid. The reliable CT findings for abscess were: (i) rim enhancement >50% of the circumference, 54% sensitive, 71% specific, and 62% accurate; and (ii) severe soft tissue manifestations, 39% sensitive, 92% specific, and 64% accurate. There were no significant differences in the anatomic spaces involved, the maximum transverse diameter, margin, attenuation, and gas bubbles between abscess and non-infected fluid. Conclusion: CT findings that may help differentiate postoperative neck abscess from non-infected fluid were rim enhancement >50% of the circumference and severe soft tissue manifestations.