Human States kidney stone prevalence by age and sex

Human Research Project

Kidney Stones

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Normally, the waste product from the blood is
filtered through the kidneys, but when it over accumulates, it may produce
kidney stones. Kidney Stones are small, solid pebbles that are made of minerals
and salts that form within your kidneys, and it may become painful. There could
many reasons for the formation of kidney stones because it implicates
environmental and metabolic risk factors. Kidney stones mostly happen to
adults, but children and teenagers can get them, too.  There are several treatments; how to treat it
will depend on the type, the size and the location of the stones either in the
kidneys or the urinary tract.

Kidney stones affect about 5% of the world
population. The peak age for kidney stones is between 20 years old and 50 years
old. Furthermore, the probability of having it is more in men than in women
(Figure 1). 

Figure 1 United
States kidney stone prevalence by age and sex

Kidney stones occur in the urinary system. The
urinary system is made of different organs, such as the kidney, ureters,
urinary bladder, and urethra. The urinary system aids the body to get rid of
waste, like urea. It also keeps chemicals, such as potassium and sodium, and
water in check.

The excretory system is conformed of other
different systems: urinary system, respiratory system, biliary system, and
integumentary system. The main job of the excretory system is to eliminate all
waste the body produces that would otherwise interfere with cellular function;
it also regulates the content of the body’s fluid by limiting what and how much
can go out. In other words, the body seeks to be in homeostasis to prevent any
damage. To make it simple, without the mechanisms that allow the human system
to eliminate wastes, humans would die of intoxication, as is the case when the
kidneys or the liver stop working. A clear example of the excretory in action
is when cellular respiration produces carbon dioxide and it is removed from our
system by an effective circulatory system and respiratory system, which are
part of the excretory system.

There are several organs and structures that are
involved in the excretory system: kidneys, ureter, urinary bladder, urethra,
lungs, skin, some glands, etc. But the ones affected by kidney stones are only
in the urinary system: kidneys, ureter, bladder, prostate, urethra. Arguably, the kidneys are the most important organs of this system. They
do three essential things that help to balance the body: purifying the blood
(table 1.1), regulating blood pressure and the amount of water in the body, and
synthesizing hormones, like erythropoietin which controls red blood cell
production. Once the kidneys have separated all waste, the urine goes from the
kidneys to the bladder through the ureter which are muscular tubes that are
about 28 centimetres long. Next, urine ends up in the bladder where it is
stored allowing it to be occasional. Finally, the urethra, the tube that
connects the bladder with the meatus, leads the final part of the urinary
system. The urine leaves the body through it


Kidneys are very effective in eliminating waste
from the blood. Nevertheless, under certain circumstances, such as chronic
dehydration, some waste may accumulate in the kidney. As these microscopic
crystals (waste) stick to each other, they become a larger and larger,
reaching, in some extreme cases, more than 10centimetres wide. 

Certainly, there are different kind of kidney
stones. In other words, they can be made of different substances. There is
calcium, struvite, uric acid, and cystines stones.  There are several factors that could
produce these type of stone; for example, many foods have oxalate, such as nuts
and chocolate. High quantities of vitamin D may also contribute to calcium
stones. Struvite stones often form only due to an infection. The problem with
these stones is their fast grow rate and its often lack of symptoms. Uric acid
stones are normally present in people who don’t drink enough liquids and/or eat
food with high levels of proteins. Furthermore, there certain genetic factor
that may influence the formation of them. Lastly, cystine stones form
exclusively in people with certain hereditary issues that provoke the kidney to
make an excessive amount of specific amino acids that produce them.

Usually, a kidney stone doesn’t show any symptoms
until it is moving because it is formed of many microscopic crystals that may
cut tissue as it moves through the urinary system. 

This information brings a very interesting
question: where do kidney stones form? Kidney calcium stones usually form on
plaque, which is a deposit of calcium phosphate that forms within tissues, more
specifically in the Loops of Henle’s walls.

There are several factors that boost the
probabilities of having kidney stones: genetics, dehydration, obesity, certain
surgeries. First, family history of the disease increases the chances of having
it. Dehydration play an important role in kidney stone formation; people who
live in warm and humid environments tend to have more risk of it. There is a
correlation between obesity and kidney stones.

Although, symptoms can provide enough information
to set the basis, they cannot deliver enough data to discern what type of
stones is, until a full diagnosis have been done. Several diagnosis can be

Ultrasound scan

Computed tomography

Blood test

Urine test

Analysis of passes stones

Medical history

Simple x-ray is not recommended because only
calcium stones are easy to identify. Struvite stones are harder to find, and
uric acid stones do not appear at all. With that being said, x-ray is useful to
figure out how favorable a treatment for calcium stones was.

Usually, small stones pass through the urinary
system, but when there are bigger stones, treatment is necessary. The kind of
treatment depends on several factors: size, composition, location of the stone,
as well as symptoms and medical history. There are invasive and non-invasive
treatments. The are many types of treatments from drinking plenty of fluids to Nephrolithotomy.
The most common treatments are medication, shock wave therapy, ureteroscopy,
and nutritional therapy. When the stone is smaller than five millimetres, a
conservative management is used. This consists of a high fluid intake, as well
as a good and healthy diet, such as orange juice and oxalate restrictions. When the stone is between five and ten millimetres or
the stone has been stuck for four weeks or more after observation, medication
is often required. Normally, it is a muscle-relaxing
medication. Muscle- relaxing medication, such as Tamsulosin, helps, as
its name says, with the relaxation of the muscle, making easier for the stones
to pass trough. This type of medication is for the most part used in patients
whose stone is the ureter. Finally, if the stone is bigger than ten millimetres
or it has been stuck even though medication has been given, surgery is
required. There are three main surgical options: Extracorporeal Shock Wave
Lithotripsy, Ureteroscopy, Percutaneous Nephrostolithotomy or Nephrolithotomy.
ESWL, also known as shock wave therapy, uses sound waves, thus creating
vibrations, to shatter big stones.  Percutaneous
Nephrolithotomy: an expert makes a small incision, about one centimetre, and a nephroscope
is inserted and the stones is removed. This is technique is used when the stone
is too big, in which case it must first be broken up. Finally, when the stone
is in the ureter, it is commonly removed by ureteroscopy, in which an urologist
inserts ureteroscope trough the urethra, the bladder, and the ureter and the
stone is removed.


Prevention is always the best option.
Getting rid of the problem even before it is there. When kidney stones are treated
without any medication, they often come back. A life style change is needed. Medication
also may be needed. The main suggestion is to drink more water. . Another recommendation is eating less
food having oxalate, like nuts, chocolate, sweet potatoes, tea, and soy. It is
also essential to reduce the intake of salt and animal proteins; replacing them
with salt substitute and legumes. . Medication also
play a significant role in preventing new stones. Thiazide diuretics are used
to reduce the excretion of calcium. Potassium citrate helps keep calcium stones
from forming. Finally, Allopurinol reduces the levels of uric acid in the blood
and urine.

Outlook: Kidney stones rarely
cause long lasting damage. Usually, small kidney stones pass within one or two
weeks. But timing changes depending on the size and other factors. Kidney
stones do not cause any pain until they are in the ureter because this muscle
is not made for stretching. Therefore, it causes an excruciating pain. They can
be removed without any lasting damage to the urinary system. Although, it may
cause infection or damage to the kidney if the stones are not removed early. Treatment
usually solves the problem, this is often because the cause is not found or treated. Consequently,
prevention plays a decisive role in the outlook of kidney stones.


In conclusion,