Differences and similarities of cytomegalovirus and pneumocystis pneumonia in HIV-negative immunocompromised patients thin section CT morphology in the early phase of the disease.

The purpose of this study was to assess CT morphology of pneumocystis pneumonia (PcP) and cytomegalovirus (CMV) pneumonia for specific characteristic features, similarities as well as differences, which might contribute to an early diagnosis and, therefore, influence patient management 58 patients were included, 31 with CMV pneumonia and 27 with PcP. All patients with CMV pneumonia had underlying haematological malignancies (n = 31) mainly treated by haematopoietic cell transplantation (HCT) (n = 26). Patients with PcP had haematological malignancies (n = 17) treated by HCT in 6, solid tumours (n = 5) and corticosteroid therapy (n = 5). Thin section CTs were analysed retrospectively by two radiologists. 18 CT morphological criteria were evaluated for presence or absence. Significance was calculated by chi2 test. Interobserver correlation was tested by kappa-statistic (K) Only 5 of the 18 features were found to have significantly different frequencies in the two entities. Apical distribution (p<0.01), mosaic pattern (p<0.01) and homogeneous structure of ground-glass opacities (GGO) (p<0.05) were found more frequently in PcP (each K: 0.7-0.9), whereas small nodules or unsharp demarcation of GGO and consolidation were typical of CMV pneumonia (p<0.05). Peripheral sparing, consolidation and septal thickening inter alia were found equally in both groups In conclusion analysis of craniocaudal distribution, demarcation and structure of infiltrates may be helpful in prioritizing differential diagnosis of CMV pneumonia or PcP. However, some features thought typical for one or the other entities appear with similar frequency in both groups in HIV-negative patients.