We learned earlier that kidneys detoxify by secreting
toxins or filtering toxins out of the blood into urine. But how do
we know this?
The best way to learn what kidneys do is to examine the
product of their function- urine. Examining the urine is also a good
way to know if anything is wrong with kidney function. Medical technicians
in hospitals and clinics routinely examine urine ("urinalysis")
looking for any abnormalities. Any abnormalities could signal
kidney disease. Examples of diseases that can be detected by urinalysis
kidney stones, and chronic infections of the urinary
||Kidneys stones, after they have been
concentrated and removed from urine. Such stones in the urine can
block urine formation and cause severe pain.
Urine is analyzed
in three ways:
- Unmagnified ("macroscopic"): check for amount,
- Chemical analysis with a "dip stick": check
for acidity, density, amount of protein, glucose, ketones,
and white blood cells.
Special tests can be done for other substances, such
as illegal drugs.
- Magnified (microscopic): check for crystals,
squamous (flat) cells, bacteria,
and other large objects.
- Not enough urine might mean that the kidneys are not
filtering blood well.
- Too much urine might mean that the kidneys are not
reabsorbing the water that is filtered out of blood - a common sign
of diabetes mellitus.
- Urine should be yellow. If it is pale or clear it may
mean dilution, either because too much water is being lost or it could
be that you just drank a lot of liquid.
- Urine should be near neutral (pH=7), neither acidic nor basic.
- Presence of the substances listed above may indicate
that the kidney is not cleaning the blood adequately or that the body
contains more of the substance than even normal kidneys can handle.
- Red blood cells should not be in urine, unless the urine
is collected from females during menstruation.
- White blood cells should not be in urine. They could
indicate infection of the kidneys, bladder, or other parts of the urinary
- Too many crystals and stones could indicate a risk
for blockage of the urinary tract. This prevents urine from being discharged,
puts pressure on the kidney tubules, and stops urine formation.
Kidneys can become physically damaged by precipitates
such as stones or by excess pressure (high blood pressure, obstructions
in the bladder or the tube (urethra) that leads outside the body). The
damage can progress to renal
insufficiency and end-stage kidney disease,
which require renal dialysis
or a kidney transplant.