The renal vein is the primary blood vessel responsible for carrying filtered, deoxygenated blood away from the kidney and delivering it to the inferior vena cava. While kidneys filter waste products from the blood, they also consume oxygen and glucose to perform this work, resulting in the blood leaving the organ being deoxygenated.

B. renal artery: This vessel carries oxygenated blood from the heart (via the abdominal aorta) to the kidneys for filtration.

C. venules: While venules are small vessels that collect blood from capillaries within the kidney tissue, they are internal components that eventually merge into the renal vein rather than being the final vessel that takes blood away from the organ as a whole.

D. capillaries are the site of exchange (such as in the glomerulus or peritubular network) within the kidney; they do not take blood away from the organ but instead transition blood from the arterial to the venous system.