Pleural effusions: patterns on ventilation-perfusion lung scans

Perfusion and ventilation abnormalities created by pleural effusions can interfere with the interpretation of the lung scan. This retrospective study identified and evaluated the specificity of scintigraphic patterns for pleural effusion. Ninety-two ventilation-perfusion lung scans were analyzed for the following signs of pleural effusion: presence of fissures, straightened or concave lung borders, costophrenic angle blunting, and attenuation of lung activity by interposed fluid. The findings later were correlated with chest radiographs. Of 25 pleural effusions detected by chest radiography, scintigraphy predicted 14 (specificity, 86%). In all of these cases, there was agreement with the chest radiograph (specificity, 100%). The fissure sign and the straight-concave border sign were equally reliable for the prediction of pleural fluid. Costophrenic angle blunting was never seen as the sole indicator of pleural fluid, and attenuation was seen alone in only one case. Another finding observed during this evaluation was absent ventilation at the lung base with preserved perfusion. Scintigraphic patterns may not be reliable in obstructive lung disorders and diseases with altered lung compliance. The recognition of scintigraphic patterns of pleural effusions on ventilation-perfusion scans can improve the clinical value of lung scintigraphy by reducing the number of indeterminate readings.