Visualization of differences in soft-tissue densities. The liver in ascites.

The lateral liver border was demonstrated on the plain radiograph in 54 of 100 proved cases of ascites. The etiology of ascites, the density of the fluid, and the total protein content were similar whether the border was visualized or not. Tomography of the right upper quadrant indicated that the lateral liver margin is visualized in ascites as a result of contact between the liver and the surrounding fluid. Radiography of autopsied livers submerged in fluid demonstrated distinguishable differences in object density, and photodensitometry of the plain radiographs revealed a difference in blackness where the fluid and liver made contact. Comparison of mean liver density and mean ascitic fluid density showed a difference of 5%. These findings indicate that differences in soft-tissue densities (excluding fat) can be distinguished on the plain radiograph.