Thoracic CT findings of novel influenza A (H1N1) infection in immunocompromised patients

Abstract

The goal of this study is to describe the spectrum of initial and follow-up CT findings of novel influenza A (H1N1) infection in a series of immunocompromised patients. Eight immunocompromised patients with documented novel influenza A (H1N1) had CT imaging at our institution between May 2009 and August 2009. A total of 20 CTs (initial and follow-up) were reviewed for the presence, severity, and distribution of the following: ground glass opacity, consolidation, interlobular septal thickening, mosaic perfusion, airway wall thickening, airway dilatation, nodules, cysts, pleural effusion, pericardial effusion, lymphadenopathy, and air trapping. The most common findings were airway thickening/dilatation, peribronchial ground glass opacity, centrilobular nodules, and tree-in-bud opacities. Peripheral consolidation involving the lower lobes was also a common pattern. Findings frequently involved all lobes and were closely associated with either large or small airways. Two patients presented with atypical CT findings including focal lobar consolidation and patchy lower lobe consolidation with soft tissue centrilobular nodules. Most survivors showed near complete resolution of findings within 35 days. CT scans in immunocompromised patients with novel influenza H1N1 commonly show a strong airway predominance of findings or peripheral areas of consolidation involving the lower lobes. A subset of patients with novel influenza A (H1N1) will show findings not typical of viral infection.

Fig. 1

A 58-year-old man with novel influenza A (H1N1) and history of allogenic stem cell transplant. Axial maximum intensity projection shows patchy bilateral GGO with a peribronchial distribution. Note the small nodular regions of GGO adjacent to some of the distal vessels (arrows)

Fig. 2

A 51-year-old, male, liver transplant recipient with novel influenza A (H1N1). Axial CT demonstrates patchy bilateral GGO and consolidation with a peribronchial distribution. There is also airway thickening associated with these abnormalities

Fig. 3

A 36-year-old man with novel influenza A (H1N1) and Hodgkin’s lymphoma s/p autologous stem cell transplant complicated by graft vs. host disease. a Axial CT demonstrates patchy bilateral peribronchial consolidation, GGO, centrilobular nodules, and airway thickening typical of the airway-centric nature of novel influenza A (H1N1). The differential density between the central and peripheral lung is due to graft vs. host disease and pre-existed the other acute findings. b CT image at the lung base demonstrates patchy soft tissue centrilobular nodules with tree-in-bud opacities (arrow)

Fig. 4

A 43-year-old man with novel influenza (H1N1) s/p autologous stem cell transplant. Axial CT demonstrates peripheral posterior bilateral lower lobe consolidation in addition to more diffuse ground glass opacity

Fig. 5

A 48-year-old man with novel influenza A (H1N1), HIV, and Burkitt’s lymphoma. CT demonstrates focal non-segmental right upper lobe consolidation. This was the only significant abnormality detected

Fig. 6

A 31-year-old, female, lung transplant recipient with novel influenza A (H1N1). High-resolution CT scan demonstrates focal soft tissue centrilobular nodules progressing to lobular consolidation within the left lower lobe. While these findings are associated with the distal airways, this finding is more commonly seen with bacterial bronchopneumonia

Fig. 7

A 51-year-old, male, liver transplant recipient with novel influenza A (H1N1). a Initial CT demonstrates patchy peribronchial consolidation and GGO in the lower lobes. b Interval follow-up CT performed 26 days later shows near complete resolution of the previously seen abnormalities

Fig. 8

A 66-year-old man with novel influenza A (H1N1), diabetes, and renal failure. a Axial CT demonstrates extensive, patchy bilateral GGO and consolidation without a distinct peribronchial or subpleural distribution. b Follow-up CT demonstrates worsening of dependent consolidation, primarily in the lower lobes. While there has been improvement in some of the non-dependent regions of consolidation, the patient has developed more confluent GGO, typical of diffuse alveolar damage. This patient also has pneumomediastinum from alveolar rupture