Introduction, Types and Risk factors
Stone disease is a very common urological disease. Kidney stones can
cause the most unbearable pain, but sometimes kidney stones can exist
silently without any symptom. Stone disease can cause urinary tract
infection and can damage the kidney if not treated adequately. Once a
stone occurs, its recurrence is common. So understanding, prevention
and care of stone disease is essential.
What is a kidney stone?
A kidney stone is a hard crystal mass formed within the kidney or urinary
tract. Increased concentration of crystals or small particles of calcium,
oxalate, urate, or phosphate in urine is responsible for stone formation.
Millions of crystals of these substances in urine aggregate, gradually
increase in size, and after a long period of time, form a stone.
Normally, urine contains substances that prevent or inhibit the aggregation
of crystals. Reduced levels of stone inhibitor substances contribute to
the formation of kidney stones. Urolithiasis is the medical term used to
describe urinary stones. It is to be noted that the composition of gall
stones (found in the gall bladder) and kidney stones is different.
What are the size, shape and location of urinary stones?
Kidney stones vary in size and shape. They can be smaller than a grain
of sand or can be as large as a tennis ball. The shape of the stone may
be round or oval with a smooth surface, or they can be irregular or
jagged with a rough surface. Stones with a smooth surface cause less
pain and their chances of natural removal are high. On the other hand,
kidney stones that have an irregular rough surface can cause more pain
and are less likely to come out on their own. Stones can occur anywhere
in the urinary system but occur more frequently in the kidney and then
descend into the ureter, sometimes lodging in the narrow areas of the
Stones in the urinary tract are an important
cause of unbearable abdominal pain.
What are the types of kidney stones?
There are four main types of kidney stones:
1. Calcium Stones:
This is the most common type of kidney stone,
which occurs in about 70 - 80% of cases. Calcium stones are usually
composed of calcium oxalate and less commonly, of calcium phosphate.
Calcium oxalate stones are relatively hard and difficult to dissolve with
medical management. Calcium phosphate stones are found in alkaline
2. Struvite Stones:
Struvite (Magnesium ammonium phosphate) stones
are less common (about 10 - 15%) and result from infections in the
kidney. A struvite stone is more common in women and grows only in
3. Uric Acid Stones:
Uric acid stones are not very common (about 5
- 10%) and are more likely to form when there is too much uric acid in
the urine and urine is persistently acidic. Uric acid stones can form in
people with gout, who eat a high animal protein diet, are dehydrated or
have undergone chemotherapy. Uric acid stones are radiolucent, so
are not detected by an X-ray of the abdomen.
4. Cystine Stones:
Cystine stones are rare and occur in an inherited
condition called cystinuria. Cystinuria is characterized by high levels of
cystine in the urine.
Urinary stone occurs most frequently
in the kidney and ureter.
What is a staghorn stone?
A staghorn calculus is a very large stone, usually struvite, occupying a
large part of the kidney and resembling the horns of a stag (deer), thus
it is called staghorn. A staghorn stone causes minimal or even no pain,
diagnosis is missed in most of the cases and end result is damage to
Which factors contribute to the formation of urinary stone?
Everyone is susceptible to stone formation. Several factors that increase
the risk of developing kidney stones are:
- Reduced fluid - especially decreased water intake and dehydration.
- Family history of kidney stones.
- Diet: consuming a diet high in animal protein, sodium and oxalate,
but low in fiber and potassium rich citrus fruits.
- 75 % of kidney stones and 95% of bladder stones occur in men.
Men between the age of 20 to 70 years and those who are obese
are most vulnerable.
- A person who is bed-ridden or immobile for a long period.
- A person living in a hot humid atmosphere.
- Recurrent urinary tract infections and blockage to the flow of urine.
- Metabolic diseases: hyperparathyroidism, cystinuria, gout etc.
- Use of certain medications such as diuretics and antacids.
Reduced water intake and family history of kidney stones
are two most important risk factors for stone formation.
Symptoms and Diagnosis
CHP. 19. Stone Disease 129.
What are the symptoms of a urinary stone?
The symptoms of urinary stone may vary with size, shape, and location
of the urinary stone. Common symptoms of urinary stone are:
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Characteristics of abdominal pain due to urinary stone
- Abdominal pain.
- No symptoms. Accidental detection of urinary stone on routine health
checkups or during the workup for unrelated conditions. Stones
that do not cause any symptoms and are detected accidentally on
radiological examinations are known as “silent stones.”
- Frequency of urination and persistent urge to urinate is found in
patients with a urinary bladder stone.
- Nausea or vomiting.
- Passage of blood in urine (hematuria).
- Pain and/or burning while passing urine.
- If the bladder stone gets stuck at the entrance to the urethra, the
flow of urine suddenly stops during urination.
- Passage of stones in urine.
- In a few cases urinary stones can cause complications such as
recurrent urinary tract infection and obstruction of the urinary tract,
causing temporary or permanent damage to the kidney.
- The severity and the location of the pain can vary from person to
person depending upon the type, the size and the position of the
stone within the urinary tract. Remember, the size of the stone does
not correlate with the severity of pain. Smaller-sized rough stones
usually cause more severe pain than bigger-sized smooth stones.
- Stone pain can vary from a vague flank pain to the sudden onset of
severe unbearable pain. Pain is aggravated by change of posture
and vehicular jerks. The pain may last for minutes to hours followed
by relief. Waxing and waning of pain is characteristic of a stone
passing down the ureter.
- The abdominal pain occurs on the side where the stone is lodged.
Classical pain of kidney and ureteric stone is the pain from loin to
groin and is usually accompanied by nausea and vomiting.
- A bladder stone may also cause lower abdominal pain and pain
during urination, which is often felt at the tip of the penis in males.
- Many people who experience sudden severe abdominal pain from
stone in the urinary tract rush to seek immediate medical attention.
Abdominal pain and blood in urine strongly
indicate the presence of urinary stones.
Can kidney stones damage the kidney?
Yes. Stones in the kidney or ureter can block or obstruct the flow of
urine within the urinary tract. Such obstruction can cause dilatation of
the urinary pelvis and calyces in the kidney. Persistent severe dilatation
due to blockage can cause kidney damage in the long term in a few
Diagnosis of urinary stones
Investigations are performed not only to establish diagnosis of urinary
stones and to detect complications but also to identify factors which
promote stone formation.
The KUB ultrasound is an easily available, less
expensive and simple test that is used most commonly for the diagnosis
of urinary stones and to detect the presence of obstruction.
KUB X-ray :
Size, shape and position of the urinary stones can be
seen on the X-ray of the kidney-ureter-bladder (KUB). A KUB X-
ray is the most useful method to monitor presence and size of stone
before and after treatment of calcium containing stones.It cannot be
used to identify radiolucent stones such as those containing uric acid.
CT scan of the urinary system is an extremely accurate and
themost preferred diagnostic method to identify stones of all sizes and
to determine the presence of obstruction.
Intravenous urography (IVU):
Less frequently used, IVU is very
reliable in detecting stones and obstruction. The major benefit of IVU
is that it provides information about the function of the kidney. Structure
of the kidney and details about ureteric dilatation is better judged by
this test. It is not useful and should not be used when the serum creatinine
Urine tests to detect infection and to measure pH of the
urine; 24 hour urine collection to measure total daily urine volume,
calcium, phosphorous, uric acid, magnesium, oxalate, citrate, sodium
Basic tests such as complete blood count, serum creatinine,
electrolytes and blood sugar; and special tests to identify certain
chemicals which promote stone formation such as calcium, phosphorus,
uric acid and level of parathyroid hormone.
Stones that pass out or are removed by different
treatment modalities should be collected for analysis. Chemical analysis
of stones can establish their composition, which helps in treatment
Beware of “Silent Stones” which cause no pain,
but are most likely to cause kidney damage.
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Prevention of urinary stones
“Once a kidney stone former, always a stone former.” Urinary stones
recur in about 50 to 70% of persons. On the other hand, with proper
precautions and treatment the recurrence rate can be reduced to 10%
or less. Thus, all patients who suffer from kidney stones should follow
Diet is an important factor that can promote or inhibit formation of
urinary stones. General measures useful to all patients with urinary stones
For diagnosis of stones in the urinary tract, CT scan,
sonography and X ray are the most important investigations.
1. Drink lots of fluid
- A simple and most important measure to prevent formation of stone
is to drink plenty of water, drink plenty of water and drink plenty of
water. Drink 12 - 14 glasses (more than 3 liters) of water per day.
To ensure adequate water intake throughout the day, carry a water
bottle with you.
- Which water to drink is a dilemma for many patients. But remember,
to prevent formation of stone the quantity of water is more important
than the quality of water.
- For stone prevention, formation of a sufficient volume of urine per
day is more important than the volume of fluid taken. To ensure that
you are drinking enough water, measure the total volume of urine
per day. It should be more than 2 - 2.5 liters per day.
- Urine color or concentration may suggest how much water you are
drinking. If you drink enough water throughout the day, the urine will
be diluted, clear and almost watery. Diluted urine suggests a low
concentration of minerals, which prevents stone formation. Yellow,
dark, concentrated urine suggests inadequate water intake.
- To prevent stone formation make it a habit to drink two glasses of
water after each meal. It is particularly important to drink two glasses
of water before going to bed and an additional glass at each night
time awakening. If you need to wake up several times during the
night to urinate, you have probably drunk enough fluids during the day and night.
- Higher fluid intake is recommended in physically active people on
hot days, because a significant amount of water is lost through
- Intake of fluids such as coconut water, barley or rice water, citrate-
rich fluids such as lemonade and pineapple juice, helps in increasing
total fluid intake and prevention of stone.
Plenty of fluid intake is the simplest and most essential
measure for prevention and treatment of urinary stone.
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Which fluids are preferred to prevent urinary stone?
Intake of fluids such as coconut water, barley or rice water and citrate-
rich fluids such as lemonade, tomato juice or pineapple fruit juices helps
in the prevention of stone. But remember that at least 50% of the total
fluid intake should be water.
Which fluids should be avoided by a person with urinary
Avoid grapefruit, cranberry and apple juice; strong tea, coffee, chocolate
and sugar sweetened soft drinks such as colas. These beverages have been associated with
an increased risk of stone formation.
2. Salt restriction
Avoid excessive salt intake in diet. Avoid pickles, chips and salty snacks.
Excessive quantities of salt or sodium in the diet can increase the excretion
of calcium into the urine and thereby increase the risk of formation of
calcium stones. Sodium intake should be restricted to less than 100
mEq or 6 grams table salt per day to prevent stone formation.
3. Decrease intake of animal protein
Avoid non-vegetarian food such as mutton, chicken, fish and egg. These animal foods contain high uric acid/purines and can increase the risk of
uric acid and calcium stones.
Clean, transparent, water- like urine
denotes adequate fluid intake.
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4. Balanced diet
Eat a balanced diet with more vegetables and fruits that reduces acid
load and tend to make urine less acidic. Eat fruits such as banana,
pineapple, blueberries, cherries, and oranges. Eat vegetables such as
carrots, bitter gourd (karela-ampalaya), squash and bell peppers. Eat
high-fiber containing foods such as barley, beans, oats, and psyllium
seed. Avoid or restrict refined foods such as white bread, pastas, and
sugar. Kidney stones are associated with high sugar intake.
5. Other advice
Restrict intake of vitamin C to less than 1000 mg per day. Avoid large
meals late at night. Obesity is an independent risk factor for stone
1. To prevent calcium stone
It is a wrong concept that calcium should be avoided by
patients suffering from kidney stones. Eat a healthy diet with calcium,
including dairy products, to prevent stone formation. Dietary calcium
binds with oxalate in the gut which limits intestinal oxalate absorption
and subsequently reduces stone formation. On the other hand, when
dietary calcium is reduced, unbound oxalate in the gut can be easily
absorbed from the intestines to promote formation of oxalate stones.
- Avoid calcium supplements as well as a diet that is low in calcium,
because both increase the risk of stone development. Dietary sources of calcium such as dairy products are preferred over oral calcium
supplements for patients at risk for the development of kidney stones.
If oral calcium supplements are necessary, they should be taken
with meals to reduce the risk.
Medication: Thiazide diuretics are helpful in the prevention of calcium
stones because they limit the excretion of calcium in the urine.
Restriction of salt intake in diet is very important
for the prevention of calcium stones.
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2. To prevent oxalate stone
People with calcium oxalate stones should limit foods high in oxalate.
Foods rich in oxalate include:
3. To prevent uric acid stone
Vegetables: spinach, rhubarb, okra, (lady finger), beets and sweet
Fruits and dry fruits: strawberries, raspberries, chiku, amla, custard
apples, grapes, cashew nuts, peanuts, almonds and dried figs.
Other foods: green pepper, fruit cake, marmalade, dark chocolate,
peanut butter, soybean foods and cocoa.
Drinks: grapefruit juice, dark colas, and strong or black tea.
- Avoid all alcoholic beverages.
Avoid foods high in animal protein such as organ meat (e.g. as brain,
liver, kidney), fish especially those without scales (e.g. anchovies,
sardines, herring, trout salmon), pork, chicken, beef and egg.
Restrict pulses, legumes like beans or lentils; vegetables like
mushrooms, spinach, asparagus and cauliflower.
Restrict fatty foods such as salad dressings, ice cream, and fried
- Medication: Allopurinol to inhibit uric acid synthesis and decrease
urinary uric acid excretion. Potassium citrate to maintain urine alkaline,
as uric acid precipitates and forms stones in acidic urine.
- Other measures: weight reduction. Obese patients are not able to
alkalinize urine and this increases the risk for the formation of uric
Beware. Restriction of calcium in the
diet will promote stone formation!
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Treatment of urinary stones
Factors determining the treatment of urinary stones depend on the degree
of symptoms; size, position and cause of stone; and presence or absence
of urinary infection and obstruction. Two major treatment options are:
A. Conservative treatment
B. Surgical treatment
A. Conservative Treatment
Most kidney stones are small (less than 5 mm in diameter) enough to
pass on their own within 3 to 6 weeks of the onset of symptoms. The
aim of conservative treatment is to relieve symptoms and to help stone
removal without surgical operation.
Immediate treatment of kidney stones
To treat unbearable pain a patient may require intramuscular or
intravenous administration of non-steroidal inflammatory drugs
(NSAIDs) or opioids. For less severe pain, oral medications are often
Plenty of fluid intake
In patients with severe pain, fluid intake should be moderate and not
excessive because it may aggravate pain. But in pain free periods,drink plenty of fluids, taking as much as 2 to 3 liters of water in a day.
Remember though that beer is NOT a therapeutic agent for a patient
with kidney stones.
Patients with severe colic and associated nausea, vomiting and fever
may require intravenous saline infusion to correct fluid deficit. Patient
must save the passed out stone for testing. A simple way to collect
stones that have passed out is to urinate through a strainer (sieve).
Plenty of fluid intake will flush out a large
number of small stones in urine.
Maintaining proper urine pH is essential especially for patients with uric
acid stone. Drugs like calcium channel blockers and alpha-blockers
inhibit spasms of the ureter and dilate the ureters sufficiently to allow
the passage of the ureteral stone. This is particularly helpful when the
stone is located in the ureter close to the urinary bladder. Treat associated
problems such as nausea, vomiting and urinary tract infection. Follow
all general and special preventive measures (dietary advice, medication
B. Surgical Treatment
Different surgical treatments are available for kidney stones that cannot
be treated with conservative measures. Most frequently used surgical
methods are extra-corporeal shock wave lithotripsy (ESWL),
percutaneous nephrolithotripsy (PCNL), ureteroscopy and in rare cases
open surgery. These techniques are complimentary to each other. These
procedures are performed by the urologist who decides which method
is the best for a particular patient.
Which patient, with urinary stone, needs surgical treatment?
Most patients with small stones can be effectively treated conservatively.
But surgery may be needed to remove kidney stones when the stones:
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- Cause recurrent or severe pain and do not pass out after a reasonable
period of time.
- Are too large to pass on their own. Stones > 6 mm may need
- Cause significant obstruction, blocking the flow of urine and damaging
- Cause recurrent urinary tract infection or bleeding.
Prompt surgery may be required in patients with kidney failure due to
stone obstructing the only functioning kidney or both the kidneys
Stone recurs in more than 50% cases. Instructions
for prevention are emphatically advised.
1. ESWL - Extra-Corporeal Shockwave Lithotripsy
ESWL or extra-corporeal shock wave lithotripsy is the latest, effective
and most frequently used treatment for kidney stones. Lithotripsy is
ideal for kidney stones less than 1.5 cm in size or upper ureteric stones.
In lithotripsy highly concentrated shock waves or ultrasonic waves
produced by a lithotriptor machine break up the stones. The stones
break down into small particles and are easily passed out through the
urinary tract in the urine. After lithotripsy, the patient is advised to drink
fluids liberally to flush out stone fragments. When blockage of the ureter
is anticipated after lithotripsy of a big stone, a “stent” (special soft plastic
tube) is placed in the ureter to avoid blockage.
Lithotripsy is generally safe. Probable complications of lithotripsy are
blood in urine, urinary tract infection, incomplete stone removal (may
require more sessions), incomplete stone fragmentation (which can lead
to urinary tract obstruction), damage to kidney and an elevation in blood
Advantages of lithotripsy are that it is a safe method that does not require
hospitalization, anesthesia and incision or cut. Pain is minimum in this
method and it is suitable for patients of all age groups.
Lithotripsy is less effective for large stones and in obese patients.
Lithotripsy is not advisable during pregnancy and in patients with severe
infection, uncontrolled hypertension, distal obstruction in the urinary
tract and bleeding disorders.
After lithotripsy, regular follow up, periodical checkup and strict
adherence to preventive measures against recurrence of stone disease,
Lithotripsy is an effective and most frequently used
non-operative treatment for kidney stones.
2. Percutaneous Nephrolithotomy (PCNL)
Percutaneous nephrolithotomy, or PCNL, is an effective method for
removing medium-sized or large (bigger than 1.5 cm) kidney or ureteral
stones. PCNL is the most frequently used option when other treatment
modalities such as ureteroscopy or lithotripsy have failed.
In this procedure, under general anesthesia, the urologist makes a tiny
incision in the back and creates a small tract from the skin to the kidney
under image intensifier or sonographic control. For the insertion of
instruments the tract is dilated. Using an instrument called a nephroscope,
the urologist locates and removes the stone (nephrolithotomy). When
the stone is big it is broken up using high frequency sound waves and
then the stone fragments are removed (nephrolithotripsy).
By and large PCNL is safe, but there are some risks and complications
that can arise as with any surgical treatment. Probable complications of
PCNL are bleeding, infection, injury to other abdominal organs such as
the colon, urinary leak and hydrothorax.
The main advantage of PCNL is that only a small incision (about one
centimeter) is required. For all types of stones, PCNL is the most
effective modality to make the patient totally stone-free in a single sitting.
With PCNL hospital stay is shorter and recovery and healing is faster.
PCNL is the most effective method for removal
of medium or large-sized kidney stones.
3. Ureteroscopy (URS)
Ureteroscopy is a highly successful modality for treating stones located
in the mid and lower ureter. Under anaesthesia, a thin lighted flexible
tube (ureteroscope) equipped with a camera is inserted via the urethra
into the bladder and up the ureter.
The stone is seen through the ureteroscope and, depending on the size
of the stone and the diameter of the ureter, the stone may be fragmented
and/or removed. If the ureteric stone is small, it is grasped by the grasper
and removed. If a stone is too large to remove in one piece, it can be
broken into tiny fragments using pneumatic lithotripsy. These tiny stone
pieces pass out on their own in urine. Patients normally go home the
same day and can resume normal activity in two to three days.
The advantages of URS are that even hard stones can be broken by
this method, and that it does not require incisions. It is safe for pregnant
women, obese persons, as well as those with bleeding disorders.
URS is generally safe, but, as with any procedure, risks exist. Possible
complications of URS are blood in the urine, urinary tract infection,
perforation of the ureter, and formation of scar tissue that narrows the
diameter of the ureter (ureteral stricture).
Mid and lower ureteric stones can be successfully
removed by ureteroscopy without surgery.
4. Open Surgery
Open surgery is the most invasive and painful treatment modality for
stone disease requiring five to seven days of hospitalization. With the availability of new technologies, the need for open surgery has
been reduced drastically. At present, open surgery is used only in
extremely rare situations for very complicated cases with very large
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Major benefit of open surgery is complete removal of multiple, very big
or staghorn stones in a single sitting. Open surgery is an efficient and
cost-effective treatment modality especially for developing countries
where resources are limited.
When should a patient with kidney stone consult a doctor?
A patient with kidney stone should immediately consult a doctor in case
- Severe pain in the abdomen not relieved with medication.
- Severe nausea or vomiting which prevents intake of fluid and
- Fever, chills and burning urination with pain in abdomen.
- Blood in urine.
- No urine output.
Reserve open surgery for very few patients with very
large kidney stones or when other modalities have failed.