Early diagnosis of poststernotomy mediastinitis: Are there typical findings in contrast-enhanced CT?

Objectives: Contrast-enhanced CT is the method of choice to differentiate superficial (SSWI) and deep sternal wound infection (DSWI) following sternotomy. This study focuses on the CT findings to assess if there are typical abnormalities in patients with proven DSWI.

Methods: 32 patients (22 male, 11 female, mean age 66±12 years) with clinically proven DSWI (bacterial culture from mediastinal fluid, surgically obtained inflammatory tissue) received in total 48 examinations using a 64-slice CT scanner and a standardized scanning protocol. Only initial CT scans were considered (n=32) to evaluate CT findings of acute mediastinitis. These examinations were analyzed by two experienced observers (consensus decision) for the following findings: Localized fluid collections with contrast-enhancement pre- (ps) and retrosternal (rs), increased attenuation of fat (ps/rs), free gas (ps/rs), sternal dehiscence/destruction, pleural effusion, pericardial effusion, mediastinal lymph nodes.

Results: Our patients underwent CT an average of 40±41 days after surgery (9–210 days). CT findings included localized fluid collections with contrast-enhancement (ps, 66%; rs, 94%), increased attenuation of fat (ps, 16%; rs, 41%), free gas (ps, 66%; rs, 53%), sternal dehiscence/destruction (53%), pleural effusion (75%), pericardial effusion (9%), mediastinal lymph nodes (78%). Statistical significance could be detected for retrosternally localized fluid collections with contrast-enhancement (p<0.05).

Conclusion: Our data indicate that retrosternally localized fluid collections with contrast-enhancement seem to be the key CT finding to diagnose acute mediastinitis. However, the inclusion of the other non-specific CT findings does increase the level of diagnostic confidence and may help to assess the extent of the disease.