Exploiting gravity in abdominal angiography.

The difference between the specific gravity of blood and contrast medium and the consequent tendency of contrast media to fill the lower tissues is exploited in abdominal angiography by special positioning of patients: prone for the coeliac, hepatic and mesenteric arteries, prone with the legs raised for abdominal aortography; lateral decubitus on the side of interest for renal angiography. The advantages are better parenchymal opacification, increased contrast and improved details. Gravity positioning saves time and material, and is easy to learn.