Urolithiasis is the medical term used to describe stones occurring in the urinary
tract. Other frequently used terms are urinary tract stone disease and nephrolithiasis.
Ureteral stone (or ureterolithiasis) is a kidney stone found in the ureter. To keep
things simple, the term "kidney stones" is used throughout this text.
Who Gets Kidney Stones?
The number of persons in the United States with kidney stones has been increasing
over the past 20 years. Although stones occur more frequently in men, the number
of women who get kidney stones has been increasing over the past 10 years. Kidney
stones strike most people between the ages of 20 and 40. Once a person gets more
than one stone, he or she is likely to develop others.
What Causes Kidney Stones?
Doctors do not always know what causes stones to form. While certain foods may promote
stone formation in people who are susceptible, scientists do not believe that eating
any specific food causes stones to form in people who are not susceptible.
A person with a family history of kidney stones may be more likely to develop stones.
Urinary tract infections, kidney disorders such as cystic kidney diseases, and metabolic
disorders such as hyperparathyroidism are also linked to stone formation. In addition,
more than 70 percent of patients 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, the kidneys produce too much of the amino
acid cystine. Cystine does not dissolve in urine and can build up to form stones.
With hyperoxaluria, the body produces too much of the salt, oxalate. When there
is more oxalate than can be dissolved in the urine, the crystals settle out and
Absorptive hypercalciuria occurs when the body absorbs too much calcium from food
and empties the extra calcium 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 urinary tract. Other causes of kidney stones are hyperuricosuria (a disorder
of uric acid metabolism), gout, excess intake of vitamin D, and blockage of the
urinary tract. Certain diuretics (water pills) or calcium-based antacids may increase
the risk of forming kidney stones by increasing the amount of calcium in the urine.
Calcium oxalate stones may also form in people who have a chronic inflammation of
the bowel or who have had an intestinal bypass operation, or ostomy surgery. As
mentioned above, struvite stones can form in people who have had a urinary tract
Usually, the first symptom of a kidney stone is extreme pain. The pain often begins
suddenly when a stone moves in the urinary tract, causing irritation or blockage.
Typically, a person feels a sharp, cramping pain in the back and side in the area
of the kidney or in the lower abdomen. Sometimes nausea and vomiting occur with
this pain. Later, the pain may spread to the groin. If the stone is too large to
pass easily, the pain continues as the muscles in the wall of the tiny ureter try
to squeeze the stone along into the bladder. As a stone grows or moves, blood may
be found in the urine. As the 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
If fever and chills accompany any of these symptoms, an infection may be present.
In this case, a doctor should be contacted immediately.
Sometimes "silent" stones -- those that do not cause symptoms -- are found on x-rays
taken during a general health exam. These stones would likely pass unnoticed.
More often, kidney stones are found on an x-ray or sonogram taken on someone who
complains of blood in the urine or sudden pain. These diagnostic images give the
doctor valuable information about the stone's size and location. Blood and urine
tests help detect any abnormal substance that might promote stone formation.
Dr. Cornell may decide to scan the urinary system using a special x-ray test called
an IVP (intravenous pyelogram). Together, the results from these tests help determine
the proper treatment.
Fortunately, most stones can be treated without surgery. Most kidney stones can
pass through the urinary system with plenty of water (2 to 3 quarts a day) to help
move the stone along. In most cases, a person can stay home during this process,
taking pain medicine as needed. The doctor usually asks the patient to save the
passed stone(s) for testing.
People who have had more than one kidney stone are likely to form another. Therefore,
prevention is very important. To prevent stones from forming, their cause must be
determined. Laboratory tests, including urine and blood tests, the patient's medical
history, occupation, and dietary habits all help to determine why a stone formed.
If a stone has been removed, or if the patient has passed a stone and saved it,
the lab can analyze the stone to determine its composition.
A patient may be asked to collect his or her urine for 24 hours after a stone has
passed or been removed. The sample is used to measure urine volume and levels of
acidity, calcium, sodium, uric acid, oxalate, citrate, and creatinine (a byproduct
of protein metabolism). Dr. Cornell will use this information to determine the cause
of the stone. A second 2nd hour urine collection may be needed to determine if the
prescribed treatment is working.
A simple and most important lifestyle change to prevent stones is to drink more
liquids - water is best. A recurrent stone former should try to drink enough liquids
throughout the day to produce at least 2 quarts of urine in every 2-hour period.
Patients with too much calcium or oxalate in the urine may need to eat fewer foods
containing calcium and oxalate. Not everyone will benefit from a low-calcium diet,
however. Some patients who have high levels of oxalate in their urine may benefit
from extra calcium in their diet. Patients may be told to avoid foods with added
vitamin D and certain types of antacids that have a calcium base.
Patients who have a very acid urine may need to eat less meat, fish, and poultry.
These foods increase the amount of acid in the urine.
To prevent cystine stones, patients should drink enough water each day to reduce
the amount of cystine that escapes into the urine. This is difficult because more
than a gallon of water may be needed every 24 hours, a third of which must be drunk
during the night.
Dr. Cornell may prescribe certain medications to prevent calcium and uric acid stones.
These drugs control the amount of acid or alkali in the urine, key factors in crystal
formation. The drug allopurinol may also be useful in some cases of hypercalciuria
Another way to control hypercalciuria, and thus prevent calcium stones, is by prescribing
certain diuretics, such as hydrochlorothiazide. These drugs decrease the amount
of calcium released by the kidneys into the urine.
Some patients with absorptive hypercalciuria may be given the drug sodium cellulose
phosphate. This drug binds calcium in the intestine and prevents it from leaking
into the urine.
If cystine stones cannot be controlled by drinking more fluids, the doctor may prescribe
the drug Thiola. This medication helps reduce the amount of cystine in the urine.
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. The patient's urine
will be tested on a regular basis to be sure that bacteria are not present.
If struvite stones cannot be removed, the doctor may prescribe a new drug called
acetohydroamic acid (ALIA). AHA is used along with long-term antibiotic drugs to
prevent the infection that leads to stone growth.
To prevent calcium stones that form in hyperparathyroid patients, a surgeon may
remove part or all of the parathyroid glands (located in the neck). This is usually
the treatment for hyperparathyroidism as well. In most cases, only one of the glands
is enlarged. Removing the gland ends the patient's problem with kidney stones.
Some type of surgery may be needed to remove a kidney stone if the stone:
- does not pass after a reasonable period of time and causes constant pain
- is too large to pass on its own
- blocks the urine flow
- causes ongoing urinary tract infection
- damages the kidney tissue or causes constant bleeding, or has grown larger (as seen
on follow-up x-ray studies)
Until recently, surgery to remove a stone was very painful and required a lengthy
recovery time (4 to 6 weeks). Today, treatment for these stones is greatly improved.
Many options exist that do not require major surgery.
Extracorporeal Shockwave Lithotripsy
Extracorporeal shockwave lithotripsy (ESWL) is the most frequently used surgical
procedure for the treatment of kidney stones. ESWL uses shockwaves that are created
outside of the body to travel through the skin and body tissues until the waves
hit the dense stones. The stones become sand like and are easily passed through
the urinary tract in the urine.
There are several types of ESWL devices. One device positions the patient in a water-bath
while the shockwaves are transmitted. Other devices have a soft cushion or membrane
on which the patient lies. Most devices use either x-rays or ultrasound to help
the surgeon pinpoint the stone during treatment. For most types of ESWL procedures,
some type of anesthesia is needed. In some cases, ESWL may be done on an outpatient
basis. Recovery time is short, and most people can resume normal activities in a
Complications may occur with ESWL. Most patients have blood in the urine for a few
days after treatment. Bruising and minor discomfort on the back or abdomen due to
the shockwaves are also common. To reduce the chances of complications, doctors
usually tell patients to avoid taking aspirin and other drugs that affect blood
clotting for several weeks before treatment. In addition, the shattered stone fragments
may cause discomfort as they pass through the urinary tract in the urine. In some
cases, the doctor will insert a small tube called a stent through the bladder into
the ureter to help the fragments pass. Sometimes the stone is not completely shattered
with one treatment and additional treatments may be required.
Ureteroscopic Stone Removal
Although some ureteral stones can be treated with ESWL, ureteroscopy may be needed
for mid and lower ureteral stones. No incision is made in this procedure. Instead,
the surgeon passes a small fiberoptic instrument called a ureter scope through the
urethra and bladder into the ureter. The surgeon then locates the stone and either
removes it with a cage-like device or shatters it with a special instrument that
produces a form of shockwave. A small tube or stent may be left in the ureter for
a few days after treatment to help the lining of the ureter heal.
Sometimes a procedure called percutaneous nephrolithotomy is recommended
to remove a stone. This treatment is often used when the stone is quite large or
in a location that does not allow effective use of ESWL. In this procedure, the
surgeon makes a tiny incision in the back and creates a tunnel directly into the
kidney. Using an instrument called a nephroscope, the stone is located and removed.
For large stones, some type of energy probe (ultrasonic or electrohydraulic) may
be needed to break the stone into small pieces. Generally, patients stay in the
hospital for several days and may have a small tube called a nephrostomy tube left
in the kidney during the healing process.
One advantage of percutaneous nephrolithotomy over ESWL is that the surgeon removes
the stone fragments instead of relying on their natural passage from the kidney.