The renal artery and renal vein are the blood vessels responsible for bringing blood to and taking blood away from the kidneys, respectively. Blood in the renal artery contains glucose, oxygen, and cellular waste products. In the renal vein, the blood has been filtered, and is free of cellular waste and any other impurities. Both the renal artery and vein split into multiple smaller vessels, which connect to filtration units inside the kidney called nephrons, where blood filtration takes place. Every day, the vessels carry many gallons of blood.
Both the renal artery and renal vein can be susceptible to conditions that can restrict or block blood flow. If this happens in either vessel, problems filtering the blood can result, and cellular waste products may build up in the body. The renal artery and renal vein are each more prone to these particular types of problems, and they usually worsen over time. In extreme cases, kidney failure can occur, where the kidney isn't able to filter blood properly at all.
Renal arteries can develop a condition called renal artery stenosis, where the artery hardens and narrows, accumulating plaque on its walls. This is a specific form of atherosclerosis, which is the general term for hardening of the arteries anywhere in the body. A complete blockage of the renal artery can occur if this condition is left unchecked, which can prevent the kidney from filtering blood. If significantly reduced blood flow in the artery occurs, the flow can be improved by placing a stent around the blockage site, rerouting the flow of blood so the kidney can continue to filter it.
The renal vein can develop a different condition called a thrombosis, which is a clot that blocks blood flow in the vein. A thrombosis is much more uncommon than stenosis, which can also happen in the renal vein, but it is more immediately dangerous. Blood clots don't affect the kidney as much as stenosis does, but they are dangerous because they can travel to other parts of the body through the rest of the circulatory system. Clots can get caught in small arteries or capillaries, causing an embolism, or obstruction.
If a problem does occur with the renal artery and renal vein, certain lifestyle changes can improve the condition to some degree. Exercising, controlling blood pressure, and eating a low-sodium diet can lower the risk of blood vessel problems. While these actions will not guarantee relief or guarantee that someone without these conditions will never develop them, they may help to mitigate any further damage.