What is it?
The
nephrotic syndrome is not itself a disease, but a condition that is often
caused by any of a group of diseases that damages the tiny blood-filtering
units (glomeruli) in the kidneys, where urine is made.
The
kidneys clean the blood by filtering out excess water and salt and waste products
from food. Healthy kidneys keep protein in the blood; this protein dissolved
in the blood maintains the thickness of the blood and its ability to draw
water from the tissues. But kidneys with damaged filters may let protein leak
into the urine (proteinuria). Normally, a person loses less than 150 mg of
protein in the urine in a 24-hour period. A person with nephrotic syndrome
will lose around 25 times the normal amount. This is the primary indicator
of NS.
How many people does it affect?
Every
year, about two in every 10,000 people experience nephrotic syndrome, which
is around 10,000 sufferers in the UK. Its prevalence is difficult to establish
in adults because the condition is usually a result of an underlying disease.
In children, it is diagnosed in more boys than girls, usually between 2 and
3 years of age.
As
well as the symptoms of the kidney disease itself, and the side effects of
treatment, a significant proportion of sufferers ultimately end up with kidney
failure, requiring dialysis and transplantation.
How does it affect sufferers?
In
addition to proteinuria there are three main symptoms of nephrotic syndrome
associated with protein leaking into the urine:
Edema - Swelling
Nephrotic-related swelling makes tissue puffy, soft, and impressionable to
the touch. Edema is most common in the legs and feet, especially after standing
all day. It can cause feelings of tightness in the extremities and may affect
mobility. In later stages, swelling may occur in the abdomen, hands, and around
the eyes in the morning. In later stages, the whole body may swell. Some people
gain weight after fluid builds up in their bodies for a long time.
Hypoalbuminemia
This is a low level of albumin (a protein) in the blood due to proteinuria.
Low albumin in the blood causes fluid to move from the blood into the tissue,
causing swelling. The kidney perceives the decrease of fluid in the blood
and aggressively retains as much fluid and salt as it can. This contributes
to the body's fluid-overload state.
Hypercholestrolemia - High blood cholesterol
This is common in nephrotic syndrome. In addition to albumin, other important
enzymes involved in cholesterol metabolism slip through the glomeruli, which
contribute to high blood cholesterol.
Treatment
There
is no known cure for NS. Some children who develop the condition early in
life can grow out of it by their late teens. In the intervening years the
symptoms of each relapse are treated with drugs.
Steroids
are commonly used to stop the movement of protein from the blood into the
urine, but these drugs can have serious side effects. They cause weight gain,
retard growth and can make bones brittle in later life.
If
steroids do not work, then the next line of treatment is to give highly toxic
immunosuppressive drugs, like the drugs used for chemotherapy in cancer. Unfortunately,
by this stage these will often not work, and the child will then develop kidney
failure.
Diuretics
may also be given to help in reducing the swelling that is caused by water
retention.
Complications
Nephrotic
syndrome is associated with kidney failure. The disease that causes NS can
damage the glomeruli and interfere with their ability to clean the blood.
Kidney failure can happen gradually or suddenly. At this stage sufferers are
likely to need kidney dialysis and ultimately a transplant.
Some
patients develop blood that abnormally over clots. This means that they are
at risk for developing a blood clot in the legs or in the renal veins that
transport blood from the kidney. Blood thinners may be required to prevent
this complication.
Research
A
team based at the Bristol Children's Hospital Kidney Unit are researching
the causes of NS and are looking for better forms of treatment and ultimately
a cure but funding is desperately needed to provide suitable equipment and
additional staff to further this vital research.