One in every 20 people develop a kidney stone at some point in their life. A kidney
stones(renal calculi) are solid concretions (crystal aggregations) of dissolved minerals in
urine; calculi typically form inside the kidneys or ureters. The terms (nephrolithiasis)
and (urolithiasis) refer to the presence of calculi in the kidneys and urinary tract,
Renal calculi can vary in size from as small as grains of sand to as large as grapefruit.
Kidney stones typically leave the body by passage in the urine stream, and many stones
are formed and passed without causing symptoms. If stones grow to sufficient size
before passage--on the order of at least 2-3 millimeters--they can cause obstruction of
Men are especially likely to develop kidney stones, and whites get them more often
than African American. The prevalence of kidney stones begins to rise when men
reach their 40s and continues to climb into their 70s. People who have already had
more than one kidney stone are prone to develop more stones.
Kidney stones form when there is :
a decrease in urine volume or an excess of stone-forming substances in the urine.
The most common type of kidney stone contains calcium in combination with either
oxalate or phosphate. Other chemical compounds that can form stones in the urinary
tract include uric acid and the amino acid cystine.
-A number of different conditions can lead to kidney stones:
Dehydration through reduced fluid intake or strenuous exercise without
adequate fluid replacement increases the risk of kidney stones. Obstruction to the
flow of urine can also lead to stone formation. Kidney stones associated with
infection in the urinary tract are known as struvite or infection stones.
Gout results in an increased amount of uric acid in the urine and can lead to the
formation of uric acid stones.
Hypercalciuria (high calcium in the urine), another inherited condition, causes
stones in more than half of cases. In this condition, too much calcium is absorbed
from food and excreted into the urine, where it may form calcium phosphate or
calcium oxalate stones.
kidney diseases such as renal tubular acidosis (hyperparathyroidism)
associated with an increased risk of kidney stones
Some medications also raise the risk of kidney stones. These medications
include some diuretics, calcium-containing antacids, and the protease inhibitor
Crixivan (indinavir), a drug used to treat HIV infection.
People with inflammatory bowel disease or who have had an intestinal
bypass or ostomy surgery are also more likely to develop kidney stones.
Signs & Symptoms:
Kidney stones are usually asymptomatic until they obstruct the flow of urine.
Symptoms can include acute flank pain groin, or abdomen. Changes in body position
do not relieve this pain. (renal colic), nausea and vomiting, If infection is present in
the urinary tract along with the stones, there may be fever and chills. . Kidney stones
also characteristically cause blood in the urine. Some patients show no symptoms until
their urine turns bloody—this may be the first symptom of a kidney stone. The amount
of blood may not be sufficient to be seen, and thus the first warning can be
microscopic hematuria, when red blood cells are found in the microscopic study of a
urine sample, during a routine medical test. However, not every kidney stone patient
demonstrates blood in urine, even microscopically. About 15% of proven kidney stone
patients may not show even microscopic hematuria so this is not considered a
definitive diagnostic sign.
A Simple Mechanism to Understand Stone Formation:
Imagine a glass of water containing little salt .If you add some more salt, it dissolves.
When you add more and more salt, a stage is reached when the water is no longer able
to dissolve the salt added to it. This is because the solution is supersaturated with the
salt. Above this point, any little amount of salt added to the solution will start
precipitating. This is exactly the mechanism by which stones form except that the
solution is urine and the chemical composition of the salt is different.
- There are 3 main ways by which stones form in the urinary tract:
First a crystal has to form, then it has to grow and then a large number of such grown -
up crystals has to aggregate to each other before it becomes large enough to block the
It would be comforting to know that nature has it own protective mechanisms to
prevent stone formation. Yes! There are certain substances in urine which interfere
with the growth and aggregation of crystals which are responsible for stone formation.
It is because of the presence of these substances in urine that most of us do not form
stones. The stone forming substances are kept in a dissolved state in our urine.
Diagnosis & Investigation:
Diagnosis is usually made on the basis of the location and severity of the pain.
Radiological imaging is used to confirm the diagnosis and a number of other tests can be
undertaken to help establish both the possible cause and consequences of the stone.
Ultrasound imaging is also useful as it will give details about the presence of
hydronephrosis (swelling of the kidney) suggesting the stone is blocking the outflow of
urine). It can also be used to show the kidneys during pregnancy when standard x-rays are
discouraged (damaging to the fetus).
About 10% of stones do not have enough calcium (very small stones) to be seen on
standard x-rays (radiolucent stones) and may show up on ultrasound although they typically
are seen on CT scans.
I.V.P. test The relatively dense calcium renders these stones radio-opaque and they can be
detected by a traditional x-ray of the abdomen that includes Kidney, ureters, and bladder,
This may be followed by an IVP (Intravenous Pyelogram) which requires about 50ml of a
special dye to be injected into the bloodstream that is excreted by the kidneys and by its
density helps outline any stone on a repeated X-ray. These can also be detected by similar
"dye" is injected directly into the ureteral opening in the bladder by a surgeon.
Some people might be allergic to this contrast if this the case, then this test cannot be done.
Computed tomography (CT or CAT scan), a specialized X-ray in this setting does not
require the use of intravenous contrast, which carries some risk in certain people (e.g.,
allergy, kidney damage). All stones are detectable by CT except very rare stones composed
of certain drug residues in urine.
The non-contrast "renal colic study" CT scan has become the standard test for the
immediate diagnosis of flank pain typical of a kidney stone. If positive for stones, a single
standard x-ray of the abdomen (KUB) is recommended. This additional x-ray provides the
physicians with a clearer idea of the exact size and shape of the stone as well as its surgical
-Investigations typically carried out include:
Microscopic study of urine which may show proteins, red blood cells, pus cells,
cellular casts and crystals.
Culture of a urine sample done to look for the presence of urinary tract infection
(exclude urine infection)
Blood tests: Full blood count for the presence of a raised white cell count
(Neutrophilia) suggestive of infection, a check of renal function and if raised blood
calcium blood levels (hypercalcaemia).
24-hour urine collection to measure total daily urinary volume, magnesium, sodium,
uric acid, calcium, citrate, oxalate and phosphate.
1. Conservative Management:
It is usually the treatment of choice for small stones in the kidney and ureter. Most of
such stones pass spontaneously in the urine (4 mm or less) without any need for
intervention. The probability of a stone passing down spontaneously will depend upon
the size of a stone, it’s location, shape etc. Such patients can be treated with anti-biotic
and analgesics to feel symptomatically better. Oral dissolution agents can also be given
for a considerable length of time. The patient is generally instructed to maintain a high
fluid intake ranging from 2 to 3.5 liters/day.
If a patient has severe abdominal pain associated with vomiting and fever, then
admission is usually required and intra-venous fluids may have to be given. this does not
help, then the stone may have to be removed by endoscopy.
2. Extracorporeal Shock Wave Lithotripsy (ESWL):
Shock waves are used to break up a large stone (greater than 6 mm) into smaller pieces
that can pass through the urinary system. It is a non – operative technique with no
necessity for anesthesia and involves minimal pain. Unlike the earlier open operation
treatment, ESWL does not involve any cutting of tissues and no scars are left after the
The ESWL procedure usually lasts for about 40 minutes. But depending on the size
and number of stones, more than one session may be required for proper breaking of
the stones. Patients may be required to remain in the hospital for a day for observation.
After the procedure, the patient is advice to drink more plenty of fluids. This helps in
the passage of stone fragments in the urine.
3. Ureteroscopic Stone Removal:
It is ideally suited for stones in the lower portion of the ureter. It involves the passage
of an instrument namely ureteroscope through your urinary passage. The instrument is
as thick as a pen and is about 40 cm long. You may have to be admitted in the hospital
for a few days (2-3 days) for this procedure and it has to be done under anesthesia.
A variety of other instruments can be passed in through the scope which can be used to
break the stones and remove them. Very rarely it may so happen that the stone cannot
be removed by this method in which case open surgery may be needed.
4. Percutaneous Nephrolithotripsy:
This procedure is ideally suited for very large calculi within the kidney and the upper
ureter. In this procedure, a puncture is directly made on to the kidney, the stone is seen
with a telescope, broken into fragments and the fragments removed.
In some cases, it may not be possible to remove the entire stone. So a combination of
other procedures likes ESWL
5. Open Surgery:
In some cases, it might be required. The type of open surgery will depend upon the
site and size of the stone within the urinary tract.
In 4 patients with cutaneous urinary diversion who underwent percutaneous ureteral
stone removal, similar ureteral complications developed as a result of severe ureteritis
at the site of the stone. Ureteral narrowing occurred within days of percutaneous
ureteral stone removal, progressing to complete occlusion in 2 cases. These
complications led to prolonged hospitalization and additional procedures for each
patient. One patient with an occluded ureter was lost to follow up. Two patients
responded satisfactorily to repeated ureteral dilations and prolonged stinting. One
patient underwent excision of the affected ureteral segment. The average interval
between tube placement and removal of tubes and stints was 15 weeks in 4 patients.
The average inpatient period was 24 days.
Preventive strategies include dietary modifications and sometimes also taking drugs
with the goal of reducing excretory load on the kidneys.
Drinking enough water to make 2 to 2.5 liters of urine per day.
A diet low in protein, nitrogen and sodium intake.
Restriction of oxalate-rich foods and maintaining an adequate intake of
dietary calcium is recommended. There is equivocal evidence that calcium
supplements increase the risk of stone formation, though calcium citrate
appears to carry the lowest, if any, risk.
Taking drugs such as thiazides, potassium citrate, magnesium citrate and
allopurinol depending on the cause of stone formation.
Depending on the stone formation disease, vitamin B-6 and orthophosphate
supplements may be helpful, although these treatments are generally reserved
for those with Hyperoxaluria. Cellulose supplements have also shown
potential for reducing kidney stones caused by hypercalciuria (excessive
urinary calcium) although today other means are generally used as cellulose
therapy is associated with significant side effects.
A class of drugs usually thought of as diuretic. These drugs prevent stones through an
effect independent of their diuretic properties: they reduce urinary calcium excretion.
Thiazides are the medical therapy of choice for most cases of hypercalciuria (excessive
urinary calcium) but may not be suitable for all calcium stone formers; just those with
high urinary calcium levels.
Is another drug with proven benefits in some calcium kidney stone formers. Allopurinol
interferes with the liver's production of uric acid.
Hyperuricosuria, too much uric acid in the urine, is a risk factor for calcium stones.
Allopurinol reduces calcium stone formation in such patients. The drug is also used in
patients with gout or hyperuricemia, but hyperuricosuria is not the critical feature of uric
acid stones. Uric acid stones are more often caused by low urine pH. Even relatively
high uric acid excretion will not be associated with uric acid stone formation if the urine
pH is alkaline. Therefore, prevention of uric acid stones relies on alkalinization of the
urine with citrate.
Is also used in kidney stone prevention. This is available as both a tablet and liquid
preparation. The medication will increase the urinary pH making it more alkaline as well
as increasing the urinary citrate level, which helps reduce calcium oxalate crystal
Certain foods may increase the risk of stones
spinach, rhubarb, chocolate, peanuts, cocoa, tomato juice, grapefruit juice, apple juice,
soda (acidic and contains phosphorus), and berries (high levels of oxalate). In the United
States, the South has the highest incidence of kidney stones, a region where sweet tea
consumption is very common.
Other drinks are associated with decreased risk of stones, including wine, lemonade and
orange juice, the latter two of which are rich in citrate, a stone inhibitor.
Done by: Dina