The radiographic differentiation of pulmonary oedema

A radiographic scoring system has been reported to have a high diagnostic accuracy in the differentiation of pulmonary oedema of renal, cardiac and capillary origin. In the present study, a similar scoring system was used in 51 patients with radiographic appearances of pulmonary oedema due to renal failure (n = 16), cardiac failure (n = 13) and to adult respiratory distress syndrome (ARDS) (n = 22). Evidence of increased pulmonary capillary permeability to transferrin was sought in all patients using a double-isotope method to derive a protein accumulation index (PAI). Using the clinical diagnosis of each type of pulmonary oedema as the "gold standard", sensitivity, specificity and accuracy for the chest radiographic scoring system in pulmonary oedema of cardiac origin were 46, 84 and 75%, respectively. For renal patients these values were 63, 86 and 78% and for ARDS, 89, 33 and 77%. For the PAI in ARDS, sensitivity was 85%, specificity 67% and accuracy 86%. The radiographic scoring system failed to distinguish between pulmonary oedema of renal and cardiac origin and cannot be considered of diagnostic value, but it was more successful in assessment of ARDS. Radiographic appearances suggestive of capillary injury and increased capillary permeability to transferrin occurred in all groups and such findings are not specific to ARDS as currently defined.