Water vital for kidneys
The kidney is the water filter of the human body. It allows the body
to rid itself of poisons that can be dissolved in water. The liver
gets rid of the other fat-soluble poisons.
Through the blood is the way substances are transported, so something
coming from the foot can be dissolved in the blood transported around,
until it gets to the kidney and is excreted through the urine.
To do this, several things need to happen. First, there has to be
a certain amount of water in the blood to be able to dissolve any
thing. There is a certain amount of water needed each day to carry
on the work of the kidney – it cannot work with anything less that
500ml of fluid. This is the very minimum of fluid the kidney can get
rid of, because it would need to be so concentrated that it would
not have room to get rid of the normal breakdown waste products of
the body.
Because we sweat about 500ml per day as well, we need about 1.2 litres
of water per day, as the bare minimum for the body to function. When
people talk of drinking fluids or water each day, they are working
on the basis that there is a minimum needed by the kidney.
As the amount of water increases, the amount of urine will increase
after about 30 minutes. If you drink 5 litres per day, you will excrete
about 4.5 litres and, if you drink one litre per day, you will excrete
about 500ml per day.
The difference is that the urine is more concentrated. Because urine
is more concentrated there is a risk that several things, like calcium
or uric acid (the acid that causes gout), might be in high concentrations
in the urine. Therefore, one might get precipitation in the urine
of the calcium of urate (uric acid).
The result is a kidney stone, which is more likely to form if the
urine is concentrated. Anyone who has had a kidney stone will be aware
of the pain it can cause. That pain is usually from the pressure of
the tube pushing the stone to try to make it go through the tube,
from the kidney to the bladder.
The tube (ureter) will go into a spasm as it tries to push the kidney
stone (calculi) down the tube. If the stone is near the kidney, one
will usually feel the pain high up, toward the back of the abdomen
in the area known as the loin.
If the stone moves down to the bladder, the pain is usually felt
more toward the front and lower dawn in the abdomen in the groin,
and sometimes, in men, the pain is felt in the testicle.
This is known as the loin-to-groin pain associated with kidney stones.
The best way to stop these stones in the first place is to stop the
urine from getting too concentrated, and making sure that one drinks
about 1.5 litres to 2 litres of water per day. But, if there is a
stone, the treatment will usually be to take painkillers and an antiinflammatory
medication (indomethacin, voltaren).
Sometimes, the kidney stone will get stuck as it travels down the
tube from the kidney to the bladder. The most common spot for it to
get stuck is just before the bladder. If the calculi is stuck at this
level, one might need to have an operation to remove the stone, with
a clasp inserted through the bladder and up into the ureter to pull
it out. Other times, a tube is pushed into the kidney and pushes the
stone down to the bladder and out. Another option is to blast the
stone.
Various diseases affect the kidney, and the ones most doctors worry
about are high blood pressure (hypertension) and diabetes.
Hypertension causes direct damage to the delicate filters (glomeruli)
and blood vessels in the kidney. Damaged glomeruli release chemicals
that push the blood pressure higher, creating a vicious cycle of damage
– higher blood pressure and, eventually, renal failure.
The same thing happens with diabetes. A combination of high pressure
and diabetes is the leading cause of kidney failure and subsequent
dialysis. Fortunately, the use of potent treatments and good control
of diabetes can stop most of the damage, but underscores the need
to check blood pressure regularly and know if one has diabetes, to
avoid the complications.
Dialysis is the mechanical filtering of blood needed to keep you
alive if your kidneys are not working. Often, people need to be hooked
up to a dialysis machine three times a week for about four hours each
time. This is a risky, time-consuming and restrictive business, but
people can be kept alive and often go on to have a transplant.
Again, this underlies the preferred option of looking after one’s
first set of kidneys. Poorly controlled blood pressure and diabetes
can also destroy the transplant kidney. So some people will not get
a transplant if they cannot maintain the kidney’s original condition.
Kidneys also make erythropoietin (hormone needed to make red blood
cells) and activate vitamin D to do its work managing calcium and
bone density. Generally, the advice is to look after your kidneys,
watch your blood pressure and, if you have diabetes, keep the sugars
under control so you won’t be looking for a new kidney.
