Kidney Stone

Most urinary stones originate from the kidney. From the kidneys it passes through the ureters that are tubes linking the kidneys to the bladder and through the bladder out of the body without any intervention.

Stone that cause severe recurrent symptoms or other complications may be treated by various techniques, most of which do not involve major surgery.

What is a kidney stone?

A kidney stone is a hard mass of crystals that form in the urine within the urinary tract. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. These inhibitors do not seem to work or is present in insufficient amounts in those people who form kidney stone. If the kidney stone is small, it will travel through the urinary tract and pass out of the body in the urine without being noticed.

Kidney stone may contain various combinations of chemicals. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. These chemicals are part of a person’s normal diet and make up important parts of the body, such as bones and muscles.

Another type of kidney stone is uric acid stones. This is related to high uric acid levels in the blood. It is also derived from our diet, especially one rich in proteins such as red meats, liver and certain seafood such as prawns but not fish. High uric acid may give rise to gout.

A less common type of kidney stone is caused by infection in the urinary tract. This type of kidney stone is called a struvite or infection kidney stone.

Other metabolic kidney stone such as Cystine kidney stone are rare.

Urolithiasis is the medical term used to describe urinary stone occurring in the urinary tract. Other frequently used terms are urinary tract stone disease and nephrolithiasis. Doctors also use terms that describe the location of the stone in the urinary tract. For example, a ureteral or ureteric stone—or ureterolithiasis—is a kidney stone that has dropped into the ureter which is the tube leading from the kidney to the bladder.

To keep things simple, the general term kidney stone is used here.

Gallstones and kidney stones are not related. They form in different areas of the body. Someone with a gallstone is not necessarily more likely to develop kidney stones.


What causes kidney stones?

Doctors do not always know what causes a kidney stone to form. Certain foods may promote kidney stone formation in people who are susceptible. These are people who may have low levels of inhibitors in their urine. A person with a family history of kidney stones may be more likely to develop kidney stones. Urinary tract infections, kidney disorders such as medullary sponge kidneys, and certain metabolic disorders such as hyperparathyroidism are also linked to kidney stone formation.
In addition, more than 70 percent of people with a rare hereditary disease called renal tubular acidosis develop kidney stones.

Cystinuria and hyperoxaluria are two other rare, inherited metabolic disorders that often cause kidney stones. In cystinuria, too much of the amino acid cystine, which does not dissolve in urine, is voided, leading to the formation of kidney stones made of cystine. In patients with hyperoxaluria, the body produces too much oxalate, a salt. When the urine contains more oxalate than can be dissolved, the crystals settle out and form kidney stone.

Hypercalciuria is inherited, and it may be the cause of kidney stone in more than half of patients. Calcium is absorbed from food in excess and is lost into the urine. This high level of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or elsewhere in the urinary tract.

Other causes of kidney stones are hyperuricosuria, which is a disorder of uric acid metabolism; gout; excess intake of vitamin D; urinary tract infections; and blockage of the urinary tract. Certain diuretics, commonly called water pills, and calcium-based antacids may increase the risk of forming kidney stones by increasing the amount of calcium in the urine.

Calcium oxalate kidney stone may also form in people who have chronic inflammation of the bowel or who have had an intestinal bypass operation, or ostomy surgery. Struvite kidney stone can form in people who have had a urinary tract infection. People who take the protease inhibitor indinavir, a medicine used to treat HIV infection, may also be at increased risk of developing kidney stone.


What are the symptoms of kidney stones?

Kidney stone may not cause any symptoms. The first symptom of a kidney stone may be extreme pain, which begins suddenly when a kidney stone moves into the urinary tract and blocks the flow of urine. Typically, a person feels a sharp, cramping pain at the back and side in the area of the kidney or in the lower abdomen. Sometimes nausea and vomiting occur. Later, pain may spread to the groin.

If the kidney stone is large, pain continues as the muscles in the wall of the narrow ureter try to squeeze the stone into the bladder. As the kidney stone moves and the body try to push it out, blood may appear in the urine, making the urine pink. As the kidney stone moves down the ureter, closer to the bladder, a person may feel the need to urinate more often or feel a burning sensation during urination.

If fever and chills accompany any of these symptoms, an infection may be present. In this case, a person should contact a doctor immediately.


How are kidney stones diagnosed?

Silent kidney stone that do not cause symptoms are found on x-rays taken during a general health exam. If the kidney stone are small, they will often pass out of the body unnoticed. Often, a kidney stone is found on an x-ray or ultrasound taken of someone who complains of blood in the urine or sudden pain. These diagnostic images give the doctor valuable information about the kidney stone’s size and location. Blood and urine tests help detect any abnormal substance that might promote stone formation.

The doctor may decide to scan the urinary system using a special test called a computerized tomography (CT) scan or an intravenous pyelogram (IVP). The results of all these tests help determine the appropriate treatment.


How are kidney stones treated?

Fortunately, surgery is not usually necessary. Most kidney stones can pass through the urinary system with plenty of water to help move the stone along. Often, the patient can stay home during this process, drinking fluids and taking pain medication as needed. The doctor usually asks the patient to save the passed kidney stone for testing. It can be caught in a cup or tea strainer used only for this purpose.


Surgical Treatment

Surgery may be needed to remove a kidney stone if it

  • does not pass after a reasonable period of time and causes constant pain
  • is too large to pass on its own or is caught in a difficult place
  • blocks the flow of urine
  • causes an ongoing urinary tract infection
  • damages kidney tissue or causes constant bleeding
  • has grown larger, as seen on follow-up x rays

Until 20 years ago, open surgery was necessary to remove a kidney stone. The surgery required a recovery time of 4 to 6 weeks. Today, treatment for a kidney stone is greatly improved, and many options do not require major open surgery and can be performed in an outpatient setting.


Extracorporeal Shock Wave Lithotripsy (ESWL)

Extracorporeal shock wave lithotripsy (ESWL) is the most frequently used procedure for the treatment of kidney stone.

In ESWL, shock waves that are created outside the body travel through the skin and body tissues until they hit the denser kidney stone. The kidney stone break down into small particles and are easily passed through the urinary tract in the urine.



Several types of ESWL devices exist. Most ESWL devices use either x-rays or ultrasound to help the surgeon pinpoint the stone during treatment. For most ESWL procedures, anesthesia is not needed.

ESWL is usually done on an outpatient basis. Recovery time is short, and most people can resume normal activities within a day.  Most patients will have some blood in their urine for a few days after treatment. Because of this, they may wish to be away from work for a few days.

To reduce the risk of complications, patients should avoid taking aspirin and other medicines that affect blood clotting such as Plavix, Persantin, Warfarin for at least a week before ESWL treatment.

Those with hypertension should also ensure their blood pressure is under control by taking their anti-hypertensive medication regularly and checking with their regular doctor if their blood pressure is well controlled.

Sometimes, the shattered kidney stone particles cause minor blockage as they pass through the urinary tract and cause discomfort. In severe and selected cases, a small tube called a stent may be inserted through the bladder into the ureter to help the fragments pass.

Most kidney stones will be shattered with one treatment with ESWL. In cases when the kidney stone is not completely shattered with one ESWL treatment, additional treatments may be needed.

As with any surgical procedure, potential risks and complications should be discussed with the doctor before making a treatment decision.


Ureteroscopic Stone Removal /Ureteroscopic Intracorporeal Lithotripsy

Although some kidney stone in the ureters can be treated with ESWL, ureteroscopy may be needed for mid- and lower-ureter stones.

No incision is made in this procedure. Instead, the surgeon passes a small fiberoptic instrument called a ureteroscope through the urethra and bladder into the ureter. This is done under general anesthesia. The surgeon then locates the stone and either removes it with a cage-like device called a stone basket or shatters it with a laser beam.

The sequence of pictures below shows a stone impacted in the ureter. The stone is fragmented with a laser and the fragments removed with a stone basket.

A small tube or stent may be left in the ureter for a few days to help urine flow. No overnight hospital stay is required. Th patient can be discharged after several hours of observation.


Percutaneous Nephrolithotripsy  (PCNL or PNL)

Sometimes a procedure called percutaneous nephrolithotripsy is recommended to remove a stone. PCNL or PNL is often used when the stone is very large, multiple or in a location that does not allow effective use of ESWL.

In PCNL or PNL, the surgeon makes a tiny key-hole incision in the back and creates a tunnel directly into the kidney. Using an instrument called a nephroscope; the surgeon locates and removes the stone. For large stones, ultrasonic, pneumatic or laser probes may be needed to break the stone into small pieces.



Hospital stay for PCNL or PNL is usually about 3 days. A small tube called a nephrostomy tube is used to drain the kidney temporarily during the healing process.

One advantage of percutaneous nephrolithotripsy or PCNL or PNL is that the surgeon can remove the kidney stone fragments directly instead of relying solely on their natural passage from the kidney.


Preventing Kidney Stones

A person who has had more than one kidney stone may be likely to form another; so, if possible, prevention is important.

In repeat stone formers, the doctor will order laboratory tests, including urine and blood tests to help determine their cause The doctor will also ask about the patient’s medical history, occupation, and eating habits. If a stone has been removed, or if the patient has passed a stone and saved it, a stone analysis by the laboratory may help the doctor in planning treatment.

A simple and most important lifestyle change to prevent stones is to drink more liquids—water is best. Someone who tends to form stones should try to drink enough liquids throughout the day.

Taking calcium in pill form may increase the risk of developing stones. Repeat calcium stone formers should avoid food with added vitamin D and certain types of antacids that have a calcium base. Someone who has highly acidic urine may need to eat less meat, fish, and poultry. These foods increase the amount of acid in the urine.

If the second stone component is oxalate, they should reduce their intake of food high in oxalate. A list of these is given below.


Foods and Drinks Containing Oxalate

People prone to forming calcium oxalate stones may be asked by their doctor to limit or avoid certain foods if their urine contains an excess of oxalate.

High-oxalate foods—higher to lower
1.    rhubarb
2.    spinach
3.    beets
4.    Swiss chard
5.    wheat germ
6.    soybean crackers
7.    peanuts
8.    okra
9.    chocolate
10.    black Indian tea
11.    sweet potatoes
Foods that have medium amounts of oxalate may be eaten in limited amounts.
Medium-oxalate foods—higher to lower
12.    grits
13.    grapes
14.    celery
15.    green pepper
16.    red raspberries
17.    fruit cake
18.    strawberries
19.    marmalade
20.    liver


Medical Therapy

A doctor may prescribe certain medications to help prevent calcium and uric acid stones. These medicines control the amount of acid or alkali in the urine; key factors in crystal formation. The medicine allopurinol may also be useful in some cases of hyperuricosuria.

For struvite stones that have been totally removed, the first line of prevention is to keep the urine free of bacteria that can cause infection. A patient’s urine will be tested regularly to ensure no bacteria are present.

People with hyperparathyroidism sometimes develop calcium stones. Treatment in these cases is usually surgery to remove the parathyroid glands, which are located in the neck. In most cases, only one of the glands is enlarged. Removing the glands cures the patient’s problem with hyperparathyroidism and kidney stones.

UroSurgery Mt. E, Urology Specialist Clinic, Singapore





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