Does blood in the renal artery has more urea than blood in the renal vein?
Does the renal artery have more or less oxygen?

What do you think? I've done my homework, your turn. I'll be happy to help you, but I can't give you the answers.

I think that blood in the renal artery has more urea than blood in the renal vein since blood goes to the kidneys through the renal artery.. but I am not sure...

Think about where the urea is produced. Is it produced within the kidney or outside of the kidney?

Inside the kidney.. and therefor oxygenated blood is taken to the renal artery and more urea is found in the renal vein... is that correct?

I'm not going to tell you if that is correct or not, rather I am going to ask you if you feel comfortable with this answer.

Look into the efferent and afferent blood (hemo/hemato) pathways and the parenchymal function of the kidney.