Illusory consolidation of the left lower lobe: a pitfall of portable radiography

The definition of the left hemidiaphragm is frequently lost when patients are evaluated with portable radiographic equipment. Experimental evidence, based on results of radiography and subsequent sagittal sectioning of a frozen, unembalmed human thorax, corroborated the authors' hypothesis that this finding is related to loss of tangential imaging of the apex of the hemidiaphragm due to cephalic angulation of the central beam accompanied by projection of extrapleural fat onto the base of the left lung. In eight of ten patients in whom portable radiography was performed in 10 degrees-15 degrees of lordosis, varying degrees of loss of definition of the left hemidiaphragm were seen, in the absence of disease. This potential pitfall can be avoided by ensuring that the central beam is tangent to the hemidiaphragm. To do otherwise can create the false impression of disease in the left lower lobe, pleural space, or both.