Diagnostic value of 99mTc-HM-PAO leukocyte scintigraphy and computer tomography in patients with sternal wound infections.

METHODS: 99mTc-HM-PAO leukocyte scintigraphy (LS) and computer tomography (CT) were carried out on 19 patients after cardiac surgery; 10 patients with a high clinical probability of an infected sternal wound (group II) and additionally 9 postoperative patients without clinical symptoms of infection, as a control group (group I). LS was carried out with mixed, autologous leukocytes, labelled with 99mTc-HM-PAO in vitro. CT scans were obtained with the use of intravenous contrast material. Findings from the LS of control patients (group I) were as follows: a cold area in the view of the sternum, a 'biffed sternum' and a diffuse, increased lung uptake of leukocytes. The CT scans of the control group showed focal oedema, focal haematoma and moderate sternal abnormalities. The CT findings of a well-defined fluid collection in the retrosternal space led to one control patient being classified as having a retrosternal abscess. In the group II, the LS finding of an increased leukocyte uptake and the CT finding of a structural irregularity of the sternum, or of air or fluid collection in the retrosternal space, were taken as signs of infection. In 11 of the 13 cases, the infection was verified clinically: 9 of these proved positive on LS and 8 on CT. LS was positive in cases with either superficial or deep processes. In all cases, CT revealed whether the infection was limited to the presternal space or whether the sternum and mediastinum were also involved.
CONCLUSIONS: LS and CT are sensitive methods for the early detection of postoperative sternal wound infections. CT is superior for the exact localisation of the process, while specific signs of infection can be differentiated from those of uninfected sternotomy by the use of LS. A combination of LS and CT is suggested in the diagnosis of poststernotomy infection.