Spectrum of CT findings in nosocomial Pseudomonas aeruginosa pneumonia.

The purpose of this study was to evaluate CT findings in nosocomial Pseudomonas aeruginosa Pneumonia (PAP) and to compare features of PAP in patients with isolated P. aeruginosa cultures and those with coexistent infections. A retrospective database search revealed 28 patients with nosocomial PAP (12 men, 16 women; mean age, 57 years) in which thoracic CT had been performed within a mean of 1.7 days from the time of respiratory culture. Two chest radiologists blinded to culture data performed a consensus reading noting distribution and pattern of consolidation, ground-glass opacity, nodules, peribronchial infiltration, necrosis, effusions, and pleural enhancement. Coexistent respiratory cultures were recorded. Consolidation was present in all patients, involving multiple lobes in 23 (82%) and demonstrating upper zonal involvement in 23 (82%). Nodular features were present in 14 (50%), including tree-in-bud patterns with centrilobular distributions in 9 (64%) and larger, randomly distributed nodules in 5 (36%). Five of five patients with consolidations limited to the lower lung zones had associated upper lung nodules. Ground-glass opacity was seen in nine (31%) and peribronchial infiltration in 16 (57%). Necrosis was present in eight (29%). Thirteen (46%) bilateral and five (18%) unilateral pleural effusions were present with enhancement occurring in two (1%). Coexistent positive respiratory cultures were identified in 13 patients. The distribution of consolidation, frequency and distribution of nodules, and frequency of necrosis did not differ significantly between patients with and without other positive cultures. With CT, PAP most commonly presents with multifocal airspace consolidation. Nodular features were identified in half, with one-third demonstrating tree-in-bud opacities. Unsuspected necrosis occurred in one-third of cases. CT findings in patients with and without other respiratory isolates did not differ in the distribution and frequency of consolidations, nodularity, or necrosis.