What are Renal Stones (Kidney Stones, Renal
kidneys are bean-shaped organs, each
about the size of a clenched fist. They are located in the middle of
the back, just
below the rib cage, one on each side of the spine. The kidneys are
sophisticated filtration machines. Every day, a person's kidneys
about 200 quarts of blood to sift out about 2 quarts of waste products
extra water. The wastes and extra water become urine, which flows to
urinary bladder through tubes called ureters. The bladder stores urine
until it releases
it when a person urinates.
The kidneys are primarily responsible for filtering
metabolites and minerals from the blood circulation.
has all the ingredients that form a kidney stone, but all these ideally
pass out of the body, without our knowledge, during urination. When there is an imbalance
in metabolism or lack of fluids, the ingredients of urine form crystals
and cluster together into stones. In medical terminology, these
deposits are known as Renal Calculi. Kidney stones are clumps developed
from solidified crystals in the kidney or urinary tract. The size of
the stone / calculus can be as small as a grain of sand, to one as
large as the size of a golf ball.
stones are the commonest complaint and one of the most painful of the
urological disorders. Kidney stones may modify the victim's behaviour
with great fear of intense pain and threaten with failure of the kidney.
every twenty people develops a kidney stone at some point in their
life. Recurrence rates are very high - around 50% over a 5-10 year
period and 75% over 20 years. Men are affected approximately 4 times
more often than women. The prevalance of kidney stones begins to rise
when men reach their 40s and it continues to climb into their 70s.
who have already had more than one kidney stone are prone to develop
more stones. A family history of kidney stones is also a risk factor
for the development of kidney stones.
Causes of Renal Stones (Kidney Stones, Renal
There are many potential causes of kidney stone formation. In
general, they are the result of a superconcentration of chemicals in
the urine which form crystals and finally stones / calculi.
A disorder in metabolism, dietary habit, dehydration, recurrent
urinary tract infection and / or blockage of the urinary tract could alter
your urine concentration :
- A positive family history (genetic tendency) also makes a
person prone to kidney stone formation. Hereditary factors also
play a strong role. Hypercalciuria (where there is excess of
calcium excreted in urine) is also a genetically acquired factor
which leads to frequent development of kidney stones.
- Metabolism : Metabolic disorders are one of the main causes of
kidney or renal stones. The body is not able to assimilate the
minerals and salts such as calcium, uric acid or other salts in
the blood. Metabolism is commonly impaired in endocrine disorders
such as hyperparathyroidism, certain diseases like ulcerative
colitis and regional enteritis. In gouty arthritis, the high level
of uric acid in the urine can act as a breeding ground for calcium
oxalate stones. On the whole, the formation of kidney or renal
stones is a complex process.
- Dietary habits : Diet contributes a part in the formation of
renal or kidney stones and is considered a major maintaining
cause. Clinically, it is observed that too much of a particular
food promotes kidney or renal stones. A pregnant woman was advised
to take plenty of 'greens' to raise iron in the blood, and she
developed renal or kidney stones which came into light because of
an acute renal colic (pain). Similarly, a patient who had an
abnormal craving for 'tomatoes' is now on treatment for renal
calculi or kidney stones. Habits like 'betel chewing' with lime,
should also be considered as probable causes.
Certain foods that increase the risk
for kidney or renal stones in susceptible individuals include
spinach, strawberries, tomatoes, grapefruit juice, apple juice,
soda, and all types of teas and berries.
An imbalance of
vitamins and minerals can increase the amount of calcium oxalate
in the urine; when the levels become too high, the calcium oxalate
does not dissolve and crystals may begin to form.
- Inadequate intake of fluids : Some people do not take
sufficient water and fluids. In some people, living in areas with a high temperature causes sweating and loss of fluids. The above may lead to
long-term dehydration, resulting in concentration of urine, which
further leads to over concentration of metabolic byproducts in the
- Infection : Chronic urinary tract infection (UTI) may
predispose a person to stone formation. The slough and the crusts which
result following an infection, would combine with high levels of
minerals and salts to form stones. This is considerably noted in
the formation of vesical calculus after chronic cystitis.
- Urinary obstruction : Urinary bloackage as in prostate
enlargement, stricture urethra and limited activity for several
weeks will predispose a person to stone formation through sedimentation.
Prostatic enlargement invariably causes stones in many patients.
- Patients with inflammatory bowel disease or who have had an
intestinal bypass or ostomy surgery are also more likely to
develop kidney stones.
- Some medications also raise the risk of kidney stones which
include diuretics, calcium containing antacids and crixivan - a
drug used to treat HIV infection.
Types of Kidney Stones (Renal Stones, Renal
- Calcium oxalate stones : These kidney stones are very common
and are found in many patients. Most of these patients have
inheritated metabolic disorders, which cause increased presense of
calcium in the urine.
Consumption of low calcium diets is
actually associated with a higher risk for the development of
kidney stones. This is perhaps related to the role of calcium in
binding ingested oxalate in the gastrointestinal tract.
- Uric acid stones : These stones are not visible on X-rays.
Patients with gout often develp uric acid stones.
- Cystine stones : These type of renal stones develop due to
excessive amounts of amino acid cystine in the urine. Cystinuria
is an inherited condition and is uncommon.
- Silicate, struvite and xanthine stones are rare.
Symptoms of Kidney Stones (Renal Stones,
A stone may quietly grow for years together and may remain silent
for many years. Often, it is an incidental finding in a routine screening
for other illness/es. A kidney stone can cause problems in 2 ways :
- when it moves or
- when it grows so large that it begins to disupt kidney
function and cause damage
After keeping silent for sometime, the stone may start to move
downwards, drawn by the urine and gravity. When the stone makes its
run for freedom, it hurts the patient with severe abdominal pain
with or without nausea and vomiting causing :
- Colicky pain : The pain is 'loin to groin'. The pain may be
felt over the back or on one side, radiates to the groin, scrotum in men and
the labia in women. It is often described as 'the worst pain' ever
experienced, even more painful than gunshot, surgery, fractured
bones and so on.
- Haematuria : Blood in the urine which may look pink or
- Pyuria : Pus in the urine. Cloudy or foul-smelling urine.
- Dysuria : Buring pain on urination; more typical with
- Oliguria : Reduced urinary volume caused by obstruction of
the bladder or urethra by a stone.
- Frequent urge to urinate.
- Abdominal distension.
- Nausea or vomiting.
- Fever and chills.
- Profuse sweating.
Lab Investigations in Renal Stones (Kidney
Stones, Renal Calculi)
- An X-ray of the kidneys, ureter and bladder (KUB) or an
ultrasonography (USG) of the kidneys, ureter and bladder (KUB) can
reveal the presense of most stones.
- Intravenous pyelograms.
- Blood tests, 24 hour urine samples, provocative calcium
loading tests and stone analysis to determine the type of stone,
its underlying cause and proper course of treatment.
Diet and Nutrition in Kidney Stones (Renal
Stones, Renal Calculi)
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- Drink at least 3 litres of water every day and even more in hot
- Avoid or eat sparingly, food containing calcium oxalate
(spinach, strawberries, tomatoes, grapefruit juice, apple juice,
chocolate, celery, bell peppers, beans, asparagus, beets, soda,
and all types of teas and berries).
- Reduce uric acid by eating a low-protein diet.
- Reduce salt; higher amounts may raise the level of calcium
oxalate in your urine.
- Avoid vitamin D supplements which can increase calcium