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.
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
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