i will like to know what organ acts most directly to remove old red blood cells from circulation?

It's not the kidneys, kidneys regulate things like salt, and filter toxins and is why they have dialysis to filter these. The spleen is what filters old blood and why if we have to we can live without it. This question should be in your book somewhere, check the back for spleen. kidneys what is this? this has nothing to do with diabetes spleen

do not ask for help with your homework! Kidneys. All the blood travels through this organ to get cleansed. That's why so many diabetic people are on dialysis machines. It cleanses the blood.