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NCCN Guidelines for Patients



Kidney Cancer, Version 1.2017


Kidney cancer basics

What are the kidneys?

How the kidneys filter and clean blood

The renal arteries carry blood with waste into the


See Figure 3

. Blood then flows through

tiny filtering tubes in the kidneys called renal tubules.

Blood is “cleaned” as it flows through the renal

tubules. The renal tubules take waste and other

substances out of the blood. These substances are

made into urine.

The clean, filtered blood flows out of the kidneys

through the renal veins. The renal veins then merge

with a larger vein called the vena cava. The vena

cava takes clean blood back up to the heart.

Urine flows out of the renal tubules and collects in

a hollow space in the middle of the kidneys. This

hollow space is called the renal pelvis. Urine leaves

the renal pelvis through long tubes called ureters.

The ureters carry urine to the bladder. The bladder

holds urine until it is released from the body—when

you pee. A shorter tube, called the urethra, takes

urine from the bladder to outside the body.

Most people have two kidneys. But, each kidney

works on its own and does not need the other to

function. This means that the body can often work

well with less than one complete kidney. Many

people live full, healthy lives with only one kidney.

Figure 3

The kidneys filter blood to remove


Blood travels throughout the

body in a network of tubes called

blood vessels. Blood with waste

and extra water enters the kidney

through the renal artery. In the

kidney, renal tubules remove

excess water and other waste from

the blood to make urine. Urine

drips out of the renal tubules into

the renal pelvis then leaves the

kidney through the ureter. Clean,

filtered blood leaves the kidney

through the renal vein.

Figure 1.3 - The kidneys filter blood to remove waste

Renal artery

Renal vein


Renal pelvis

Renal tubule

Illustration Copyright © 2017 Nucleus Medical Media, All rights reserved.