Acute respiratory distress syndrome caused by pulmonary and extrapulmonaryinjury: A comparative CT study

PURPOSE: To determine computed tomographic (CT) differences between acute r espiratory distress syndrome (ARDS) due to pulmonary injury (ARDS(p)) and e xtrapulmonary injury (ARDS(ex)). MATERIALS AND METHODS: CT appearances in 41 patients (27 male, 14 female; m ean age, 47.1 years +/- 17.1 [SD]; age range, 17-79 years; those with ARDS( p), n = 16; those with ARDS(ex), n = 25) were categorized as typical or aty pical of ARDS by two observers. The extent of individual CT patterns was al so quantified. RESULTS: Typical CT appearances were more frequent in ARDS(ex) than ARDS(p) (18 [72%] of 25 vs five [31%] of 16 patients, respectively; P < .01). Sens itivity, specificity, and accuracy of a typical CT pattern for the diagnosi s of ARDS(ex) were 72%, 69%, and 71%, respectively. Atypical appearances we re characterized by more extensive nondependent intense parenchymal opacifi cation (IPO) (P = .03) and cysts (P = .05), whereas typical CT appearances had more extensive dependent IPO (P = .01). Typical appearances at CT were independently related to the cause of ARDS (odds ratio, 8.9; 95% CI: 1.8, 4 4.2; P < .01) but were independent of the time from intubation. Foci of non dependent IPO were more extensive in ARDS(p) (P = .05) than ARDS(ex), but t his finding was ascribable to differences in time to CT (after intubation) between ARDS(p) and ARDS(ex). CONCLUSION: The differentiation between ARDS(p) and ARDS(ex) can, with some caveats, be based on whether the CT appearances are typical or atypical of ARDS but not on any individual CT pattern in isolation.