Fig. 3

Left down and right down position in dehydrated and hydrated healthy subject. Common femoral veins (white arrows) appear significantly larger when dependent vs. anti-dependent in the volunteer in both left down (top left image) and right down (top middle image) positions. This is especially clear when magnified (bottom images; A = anti-dependent, D = dependent), where the anti-dependent vein appears nearly collapsed. Vein size did not appear larger when the subject was hydrated (right images)