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Urinary Stone

Urinary stone:

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,

respectively.

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

the ureter.

Incidence:

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.

Causes:

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.

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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.

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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

urinary passage.

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.

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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

orientation.

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.

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Treatment:

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

procedure.

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

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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.

Complication:

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.

Prevention:

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

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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.

thiazides

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.

Allopurinol

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.

Potassium 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

aggregation.

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