Lithotripsy

Definition
Purpose
Demographics
Description
Diagnosis/Preparation
Aftercare
Risks
Normal results
Morbidity and mortality rates
Alternatives

Definition

Lithotripsy is the use of high-energy shock waves to fragment and disintegrate kidney stones. The shock wave, created by using a high-voltage spark or an electromagnetic impulse outside of the body, is focused on the stone. The shock wave shatters the stone, allowing the fragments to pass through the urinary system. Since the shock wave is generated outside the body, the procedure is termed extracorporeal shock wave lithotripsy (ESWL). The name is derived from the roots of two Greek words, litho, meaning stone, and trip, meaning to break.

Purpose

ESWL is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube that carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications if not removed.

Demographics

For an unknown reason, the number of persons in the United States developing kidney stones has been increasing over the past 20 years. White people are more prone to develop kidney stones than are persons of color. Although stones occur more frequently in men, the number of women who develop them has been increasing over the past 10 years, causing the ratio to change. Kidney stones strike most people between the ages of 20 and 40. Once persons develop more than one stone, they are more likely to develop others. Lithotripsy is not required for treatment in all cases of kidney stones.

Description

Lithotripsy uses the technique of focused shock waves to fragment a stone in the kidney or the ureter. The affected person is placed in contact with a water-filled cushion (older machines require that the individual is actually seated in a tub of water). A sophisticated machine called Lithotripter produces the focused shock waves. A high-voltage electrical discharge is passed through a spark gap under water. The shock waves thus produced are focused on the stone inside the person’s body. The shock waves are created and focused on the stone with the help of a machine called a C-Arm Image Intensifier. The wave shatters and

KEY TERMS

Aneurysm— A dilation of the wall of an artery that causes a weak area prone to rupture.

Bladder— Organ in which urine is stored prior to urination.

Bleeding disorder— A problem related to the clotting mechanism of the blood.

Cardiologist— A physician who specializes in problems of the heart.

EKG —A graphical tracing of the electrical activity of the heart.

Extracorporeal shock wave lithotripsy (ESWL) —The use of focused shock waves, generated outside the body, to fragment kidney stones.

Gravel —The debris that is formed from a fragmented kidney stone.

Intravenous pyelogram (IVP) —A type of x ray. After obtaining an x ray of the lower abdomen, a radio-opaque dye is injected into the veins. X rays are then obtained every 15 minutes for the next hour. The dye pinpoints the location of kidney stones. It is also used to determine the anatomy of the urinary system.

Kidney stone —A hard mass that forms in the urinary tract that can cause pain, bleeding, obstruction, and/or infection. Stones are primarily composed of calcium.

Stent —A plastic tube placed in the ureter prior to the ESWL procedure, which facilitates the passage of gravel and urine.

Ultrasound —A diagnostic imaging modality that uses sound waves to determine internal structures of the body.

Ureter —A tube that carries urine from the kidney to the bladder.

Urethra —A tube that carries urine from the bladder to the outside of the body.

Urologist —A physician who specializes in problems of the urinary system.

fragments the stone. The resulting debris, called gravel, can then pass through the remainder of the ureter, through the bladder, and through the urethra during urination. There is minimal chance of damage to skin or internal organs because biologic tissues are resilient, not brittle, and because the shock waves are not focused on them.

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Lithotripsy is performed by a technician or other individual with specialized training under the supervision of a physician. The physician in charge usually has specialized training in urology. Lithotripsy is most often performed as an outpatient procedure in a facility affiliated with a hospital.

The shock wave is characterized by a very rapid pressure increase in the transmission medium and is quite different from ultrasound. The shock waves are transmitted through a person’s skin and pass harmlessly through soft tissues. The shock wave passes through the kidney and strikes the stone. At the edge of the stone, energy is transferred into the stone, causing small cracks to form on the edge of the stone. The same effect occurs when the shock wave exits the stone. With successive shock waves, the cracks open up. As more cracks form, the size of the stone is reduced. Eventually, the stone is reduced to small particles, which are then flushed out of the kidneys or ureter naturally during urination.

Diagnosis/Preparation

ESWL should not be considered for persons with severe skeletal deformities, people weighing more than 300 lb (136 kg), individuals with abdominal aortic aneurysms, or persons with uncontrollable bleeding disorders. Women who are pregnant should not be treated with ESWL. Individuals with cardiac pacemakers should be evaluated by a cardiologist familiar with ESWL. The cardiologist should be present during the ESWL procedure in the event the pacemaker needs to be overridden.

Prior to the lithotripsy procedure, a complete physical examination is performed, followed by tests to determine the number, location, and size of the stone or stones. A test called an intravenous pyelogram (IVP) is used to locate the stones, which involves injecting a dye into a vein in the arm. This dye, which shows up on x ray, travels through the bloodstream and is excreted by the kidneys. The dye then flows down the ureters and into the bladder. The dye surrounds the stones. In this manner, x rays are used to evaluate the stones and the anatomy of the urinary system. Blood tests are performed to determine if any potential bleeding problems exist. For women of childbearing age, a pregnancy

QUESTIONS TO ASK THE DOCTOR

Individuals contemplating a lithotripsy procedure should consider asking the following questions:

• Is the doctor board certified in urology?
• How many lithotripsy procedures has the doctorperformed?
• What is the doctor’s complication rate?

test is done to make sure they are not pregnant. Older persons have an EKG test to make sure that no potential heart problems exist. Some individuals may have a stent placed prior to the lithotripsy procedure. A stent is a plastic tube placed in the ureter that allows the passage of gravel and urine after the ESWL procedure is completed.

The process of lithotripsy generally takes about one hour. During that time, up to 8,000 individual shock waves are administered. Depending on a person’s pain tolerance, there may be some discomfort during the treatment. Analgesics may be administered to relieve this pain.

Aftercare

Most persons pass blood in their urine after the ESWL procedure. This is normal and should clear after several days to a week. Lots of fluids should be taken to encourage the flushing of any gravel remaining in the urinary system. Treated persons should follow up with a urologist in about two weeks to make sure that everything is progressing as planned. If a stent has been inserted, it is normally removed at this time.

Risks

Abdominal pain is fairly common after ESWL, but it is usually not a cause for worry. However, persistent or severe abdominal pain may imply an unexpected internal injury. Occasionally, stones may not be completely fragmented during the first ESWL treatment and further lithotripsy procedures may be required.

Some people are allergic to the dye material used during an IVP, so it cannot be used. For these people, focused sound waves, called ultrasound, can be used to identify where the stones are located.

Normal results

In most cases, stones are reduced to gravel and passed within a few days. Individuals may return to work whenever they feel able.

Morbidity and mortality rates

Colicky renal pain is very common when gravel is being passed. Other problems may include perirenal hematomas (blood clots near the kidneys) in 66% of the cases; nerve palsies; pancreatitis (inflammation of the pancreas); and obstruction by stone fragments. Death is extremely rare and usually due to an undiagnosed associated or underlying condition that is aggravated by the lithotripsy procedure.

Alternatives

Before the advent of lithotripsy, surgery was used to remove kidney stones. This approach is uncommon today, but occasionally used when other conditions prevent the use of lithotripsy. Attempts are occasionally made to change the pH of urine so as to dissolve kidney stones. This treatment has limited success.

Resources

BOOKS

Brenner, BM et al Brenner & Rector’s The Kidney. 7th ed. Philadelphia: Saunders, 2004.

Wein, AJ et al. Campbell-Walsh Urology. 9th ed. Philadelphia: Saunders, 2007.

PERIODICALS

Ather, M. H., and M. A. Noor. “Does Size and Site Matter for Renal Stones Up to 30 mm in Size in Children Treated by Extracorporeal Lithotripsy?” Urology 61, no. 1 (2003): 212–215.

Downey, P., and D. Tolley. “Contemporary Management of Renal Calculus Disease.” Journal of the Royal College of Surgery (Edinburgh) 47, no.5 (2002): 668–675.

Hochreiter, W. W., H. Danuser, M. Perrig, and U. E. Studer. “Extracorporeal Shock Wave Lithotripsy for Distal Ureteral Calculi.” Journal of Urology 169, no.3 (2003): 878–880.

Rajkumar, P., and G. F. Schmitgen. “Shock Waves Do More Than Just Crush Stones: Extracorporeal Shock Wave Therapy in Plantar Fasciitis.” International Journal of Clinical Practice 56, no. 10 (2002): 735–737.

ORGANIZATIONS

American Foundation for Urologic Disease. 1128 North Charles Street, Baltimore, MD 21201. (800) 242-2383 or (410) 468-1800. E-mail: admin@afud.org. www.afud.org.

American Lithotripsy Society. 305 Second Avenue, Suite 200, Waltham, MA 02451.

American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. http://www.ama-assn.org.

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201-5559. (410) 727-1100. http://www.auanet.org/index_hi.cfm.

National Kidney Foundation. 30 East 33rd Street, New York, NY 10016. (800) 622-9010, (781) 895-9098. Fax: (781) 895-9088. E-mail: als@lithotripsy.org. http://www.kidney.org.

OTHER

Case Western Reserve University. [cited March 17, 2003] http://www.cwru.edu/artsci/dittrick/artifactspages/b-21ithotripsy.htm.

Global Lithotripsy Services. [cited March 17, 2003] http://www.gls-lithotripsy.com/Howdoes.html.

Lifespan. [cited March 17, 2003] http://www.lifespan.org/mininvasive/revised/patient/gallstones/lithotripsy.htm.

National Institute of Diabetes and Digestive and Kidney Diseases. [cited March 17, 2003] http://www.niddk.nih.gov/health/urolog/pubs/stonadul/stonadul.htm#whogets.

National Library of Medicine. [cited March 17, 2003] http://www.nlm.nih.gov/medlineplus/ency/article/007113.htm.

L. Fleming Fallon, Jr, MD, DrPH

Lithotripsy

Definition

Lithotripsy is the use of high-energy shock waves to fragment and disintegrate kidney stones. The shock wave, created by using a high-voltage spark or an electromagnetic impulse outside of the body, is focused on the stone. The shock wave shatters the stone, allowing the fragments to pass through the urinary system. Since the shock wave is generated outside the body, the procedure is termed extracorporeal shock wave lithotripsy (ESWL). The name is derived from the roots of two Greek words, litho, meaning stone, and trip, meaning to break.

Purpose

ESWL is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube that carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications if not removed.

Demographics

For an unknown reason, the number of persons in the United States developing kidney stones has been increasing over the past 20 years. White people are more prone to develop kidney stones than are persons of color. Although stones occur more frequently in men, the number of women who develop them has been increasing over the past 10 years, causing the ratio to change. Kidney stones strike most people between the ages of 20 and 40. Once persons develop more than one stone, they are more likely to develop others. Lithotripsy is not required for treatment in all cases of kidney stones.

Description

Lithotripsy uses the technique of focused shock waves to fragment a stone in the kidney or the ureter. The affected person is placed in a tub of water or in contact with a water-filled cushion. A sophisticated machine called Lithotripter produces the focused shock waves. A high-voltage electrical discharge is passed through a spark gap under water. The shock waves thus produced are focused on the stone inside the person's body. The shock waves are created and focused on the stone with the help of a machine called C-Arm Image Intensifier. The wave shatters and fragments the stone. The resulting debris, called gravel, can then pass through the remainder of the ureter, through the bladder, and through the urethra during urination. There is minimal chance of damage to skin or internal organs because biologic tissues are resilient, not brittle, and because the shock waves are not focused on them.

The shock wave is characterized by a very rapid pressure increase in the transmission medium and is quite different from ultrasound. The shock waves are transmitted through a person's skin and pass harmlessly through soft tissues. The shock wave passes through the kidney and strikes the stone. At the edge of the stone, energy is transferred into the stone, causing small cracks to form on the edge of the stone. The same effect occurs when the shock wave exits the stone. With successive shock waves, the cracks open up. As more cracks form, the size of the stone is reduced. Eventually, the stone is reduced to small particles, which are then flushed out of the kidneys or ureter naturally during urination.

Diagnosis/Preparation

ESWL should not be considered for persons with severe skeletal deformities, people weighing more than 300 lb (136 kg), individuals with abdominal aortic aneurysms, or persons with uncontrollable bleeding disorders. Women who are pregnant should not be treated with ESWL. Individuals with cardiac pacemakers should be evaluated by a cardiologist familiar with ESWL. The cardiologist should be present during the ESWL procedure in the event the pacemaker needs to be overridden.

Prior to the lithotripsy procedure, a complete physical examination is performed, followed by tests to determine the number, location, and size of the stone or stones. A test called an intravenous pyelogram (IVP) is used to locate the stones, which involves injecting a dye into a vein in the arm. This dye, which shows up on x ray, travels through the bloodstream and is excreted by the kidneys. The dye then flows down the ureters and into the bladder. The dye surrounds the stones. In this manner, x rays are used to evaluate the stones and the anatomy of the urinary system. Blood tests are performed to determine if any potential bleeding problems exist. For women of childbearing age, a pregnancy test is done to make sure they are not pregnant. Older persons have an EKG test to make sure that no potential heart problems exist. Some individuals may have a stent placed prior to the lithotripsy procedure. A stent is a plastic tube placed in the ureter that allows the passage of gravel and urine after the ESWL procedure is completed.

The process of lithotripsy generally takes about one hour. During that time, up to 8,000 individual shock waves are administered. Depending on a person's pain tolerance, there may be some discomfort during the treatment. Analgesics may be administered to relieve this pain.

Aftercare

Most persons pass blood in their urine after the ESWL procedure. This is normal and should clear after several days to a week. Lots of fluids should be taken to encourage the flushing of any gravel remaining in the urinary system. Treated persons should follow up with a urologist in about two weeks to make sure that everything is progressing as planned. If a stent has been inserted, it is normally removed at this time.

Risks

Abdominal pain is fairly common after ESWL, but it is usually not a cause for worry. However, persistent or severe abdominal pain may imply an unexpected internal injury. Occasionally, stones may not be completely fragmented during the first ESWL treatment and further lithotripsy procedures may be required.

Some people are allergic to the dye material used during an IVP, so it cannot be used. For these people, focused sound waves, called ultrasound, can be used to identify where the stones are located.

Normal results

In most cases, stones are reduced to gravel and passed within a few days. Individuals may return to work whenever they feel able.

Morbidity and mortality rates

Colicky renal pain is very common when gravel is being passed. Other problems may include perirenal hematomas (blood clots near the kidneys) in 66% of the cases; nerve palsies; pancreatitis (inflammation of the pancreas); and obstruction by stone fragments. Death is extremely rare and usually due to an undiagnosed associated or underlying condition that is aggravated by the lithotripsy procedure.

Alternatives

Before the advent of lithotripsy, surgery was used to remove kidney stones. This approach is uncommon today, but occasionally used when other conditions prevent the use of lithotripsy. Attempts are occasionally made to change the pH of urine so as to dissolve kidney stones. This treatment has limited success.

See also Cystoscopy.

Resources

books

Field, Michael, David Harris, and Carol Pollock. The Renal System. London: Churchill Livingstone, 2001.

Parker, James N. The 2002 Official Patient's Source Book on Kidney Stones. Logan, UT: ICON Health, 2002.

Tanagho, Emil A., and Jack W. McAninch. Smith's General Urology, 15th ed. New York: McGraw-Hill, 2000.

Walsh, Patrick C., and Alan B. Retik. Campbell's Urology, 8th ed. Philadelphia: Saunders, 2002.

periodicals

Ather, M. H., and M. A. Noor. "Does Size and Site Matter for Renal Stones Up to 30 mm in Size in Children Treated by Extracorporeal Lithotripsy?" Urology 61, no.1 (2003): 212–215.

Downey, P., and D. Tolley. "Contemporary Management of Renal Calculus Disease." Journal of the Royal College of Surgery (Edinburgh) 47, no.5 (2002): 668–675.

Hochreiter, W. W., H. Danuser, M. Perrig, and U. E. Studer. "Extracorporeal Shock Wave Lithotripsy for Distal Ureteral Calculi." Journal of Urology 169, no.3 (2003): 878–880.

Rajkumar, P., and G. F. Schmitgen. "Shock Waves Do More Than Just Crush Stones: Extracorporeal Shock Wave Therapy in Plantar Fasciitis." International Journal of Clinical Practice 56, no.10 (2002): 735–737.

organizations

American Foundation for Urologic Disease. 1128 North Charles Street, Baltimore, MD 21201. (800) 242-2383 or (410) 468-1800. <admin@afud.org>. <http://www.afud.org>.

American Lithotripsy Society. 305 Second Avenue, Suite 200, Waltham, MA 02451.

American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. <http://www.ama-assn.org>.

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201-5559. (410) 727-1100. <http://www.auanet.org/index_hi.cfm>.

National Kidney Foundation. 30 East 33rd Street, New York, NY 10016. (800) 622-9010. (781) 895-9098. Fax: (781) 895-9088. E-mail: <als@lithotripsy.org>. <http://www.kidney.org>.

other

Case Western Reserve University. [cited March 17, 2003] <http://www.cwru.edu/artsci/dittrick/artifactspages/b-2lithotripsy.htm>.

Global Lithotripsy Services. [cited March 17, 2003] <http://www.gls-lithotripsy.com/Howdoes.html>.

Lifespan. [cited March 17, 2003] <http://www.lifespan.org/mininvasive/revised/patient/gallstones/lithotripsy.htm>.

National Institute of Diabetes and Digestive and Kidney Diseases. [cited March 17, 2003] <http://www.niddk.nih.gov/health/urolog/pubs/stonadul/stonadul.htm#whogets>.

National Library of Medicine. [cited March 17, 2003] <http://www.nlm.nih.gov/medlineplus/ency/article/007113.htm>.

L. Fleming Fallon, Jr, MD, DrPH

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Lithotripsy is performed by a technician or other individual with specialized training under the supervision of a physician. The physician in charge usually has specialized training in urology. Lithotripsy is most often performed as an outpatient procedure in a facility affiliated with a hospital.

QUESTIONS TO ASK THE DOCTOR

• Is the doctor board certified in urology?
• How many lithotripsy procedures has the doctor performed?
• What is the doctor's complication rate?

Lithotripsy

Definition

Lithotripsy is a therapeutic medical procedure used to disintegrate stones (calculi) in the urinary tract and kidneys. Extracorporeal shock wave lithotripsy (ESWL) uses shock waves generated outside the body and is noninvasive. Intracorporeal shock wave lithotripsy (ISWL) delivers shock waves through a specially designed scope used for the urinary tract (ureteroscope) and kidneys (nephroscope) and is a minimally invasive procedure. Ultrasound lithotripsy also uses a scope to deliver ultrasonic waves (mechanical vibrations) and is minimally invasive.

Purpose

Lithotripsy is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube which carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications, such as kidney damage, if not removed. Usually, stones smaller than 0.2 in (5 mm) in diameter can pass without intervention, while stones larger than 0.3 in (7 mm) in diameter require lithotripsy or the placement of a urethral or ureteral stent to help them pass. Stones larger than 10 mm require lithotripsy or surgery.

ESWL is a noninvasive alternative to open surgery (which is only very rarely performed for stones now) or percutaneous nephrolithotomy. ESWL is used in patients with stones less than or equal to 0.4 in (1 cm) located in the kidneys or ureters. ISWL is a minimally invasive endoscopic technique that is used in patients with stones over 0.4 in (1 cm), with stones in the lower urinary tract, with impacted stones, and when ESWL is unsuccessful. Both ESWL and ISWL can also be used to fragment gallbladder and bile duct stones.

Precautions

ESWL should not be considered for patients with severe skeletal deformities, patients weighing over 300 lbs (136 kg), patients with abdominal aortic aneurysms, or patients with uncontrollable bleeding disorders. Patients who are pregnant should not be treated with ESWL. Patients with cardiac pacemakers should be evaluated by a cardiologist familiar with lithotripsy. Lithotripsy may temporarily inhibit the pacemaker or cause circuit damage leading to erratic functioning or cessation of the pacemaker. The cardiologist should be present during the lithotripsy procedure in the event there are problems with the pacemaker.

Description

Lithotripsy uses focused shock waves to fragment a stone in the kidney or the ureter. In ESWL, the patient is placed on a table in contact with a water-filled cushion; and a shock wave is generated, travels through the water, and shatters and fragments the stone. Older ESWL systems involved immersing the patient in a tub of water; but this space-consuming, awkward method has been replaced by water-filled cushions. Once the stone is fragmented, the resulting gravel is left to pass on its own; the patient may have been stented prior to the procedure to widen the urethra and or ureters to allow the fragments to pass easily and with less pain. In ISWL, a ureteroscope is inserted through the urethra and bladder and into the ureters, or a nephroscope is inserted, usually through an incision in the patient's back. Once the stone is located using the endoscope, an electrohydraulic, laser, or ultrasound lithotripter can be used to fragment the stone. In ISWL using an electrohydraulic lithotripter, a probe is inserted through the endoscope and against the stone, and shock waves are delivered by a generator. In laser ISWL, a pulsed-dye laser is used to deliver laser energy through a fiber inserted through the endoscope and into the stone. Ultrasound ISWL uses a generator to produce mechanical vibrations delivered to the stone via a probe tip inserted through the generator. In ISWL, after the stone is fragmented, the pieces can be removed using a grasper or basket or left to pass on their own if they are small enough.

Preparation

Prior to the lithotripsy procedure, a complete physical examination is done, including a urine analysis, followed by imaging tests to determine the number, location, and size of the stone or stones. A test called an intravenous pyelogram, or IVP, is often used to locate the stones and determine the degree of obstruction (blockage). An IVP involves injecting a dye (contrast medium) into a vein in the arm. This dye, which shows up on x ray, travels through the bloodstream and is excreted by the kidneys. The dye then flows down the ureters and into the bladder. The dye surrounds the stones, and x rays are then used to evaluate the stones and the anatomy of the urinary system. For those patients who are allergic to the dye, ultrasound, which uses focused sound waves, or computed tomography without contrast dye is performed. Blood tests are done to determine if any potential bleeding problems exist. For women of childbearing age, a pregnancy test is done to make sure the patient isn't pregnant; and elderly patients have an elctrocardiogram (ECG) done to make sure no potential heart problems exist. Some patients may have a stent placed prior to the lithotripsy procedure. A stent is a plastic tube placed in the ureter which allows the passage of gravel and urine after the procedure is completed.

KEY TERMS

Aneurysm— A dilation of the wall of an artery which causes a weak area prone to rupturing.

Bladder— Organ in which urine is stored prior to urination.

Bleeding disorder— Problems with the clotting mechanism of the blood.

Cardiologist— A physician who specializes in problems with the heart and its vessels.

Computed tomography— An imaging examination that uses x-rays to produce a cross-sectional image of the anatomical area of interest; used to image the urinary tract and kidneys to detect kidney stones.

ECG— Electrocardiogram; a tracing of the electrical activity of the heart.

Gravel— The debris which is formed from a fragmented kidney stone.

IVP (Intravenous pyelogram)— The use of a dye, injected into the veins, used to locate kidney stones. Also used to determine the anatomy of the urinary system.

Kidney stones— Also called calculi; hard masses that form in the urinary tract and which can cause pain, bleeding, obstruction, or infection. Stones are primarily made up of calcium and can vary in size from a few millimeters to over a centimeter and more in diameter.

Nephroscope— An endoscope, a thin flexible tube with optics, used to examine the kidneys and through which intracorporeal lithotripsy can be performed.

Percutaneous nephrolithotomy— A minimally invasive endoscopic procedure involving a small incision in the back through which a nephroscope is inserted to remove stones from the kidney; used in conjunction with ISWL and after unsuccessful ESWL.

Stent— A small, short plastic tubular device placed in the urethra or ureters to widen them in order for stones and stone fragments to pass easily.

Ultrasound— Sound waves used to determine the internal structures of the body.

Ureter— A tube which carries urine from the kidney to the bladder.

Ureteroscope— An endoscope, a thin flexible tube with optics, used to examine the ureters and through which intracorporeal lithotripsy can be performed.

Percutaneous nephrolithotomy— A minimally invasive endoscopic procedure involving a small incision in the back through which a nephroscope is inserted to remove stones from the kidney; used in conjunction with ISWL and after unsuccessful ESWL.

Urethra— A tube through which urine passes during urination.

Urologist— A physician who specializes in problems of the urinary system.

Aftercare

Most patients have a lot of blood in their urine after the lithotripsy procedure. This is normal and should clear after several days to a week or so. Lots of fluids should be taken to encourage the flushing of any gravel remaining in the urinary system. The patient may be asked to urinate through a strainer and collect any stone fragments that pass for examination by the physician. Patients with stents may experience some discomfort during urination or during certain movements; this is normal. The patient should follow up with the urologist in about two weeks to make sure that everything is going as planned. If a stent has been inserted, it is normally removed at this time. Patients may return to work whenever they feel able.

Occasionally, the ESWL procedure does not break stones into pieces small enough to pass. In these cases, an endoscope may be used to remove the pieces after the ESWL procedure.

Complications

Abdominal pain is not uncommon after lithotripsy, but it is usually not cause to worry. However, persistent or severe abdominal pain may imply unexpected internal injury. Colicky renal pain is very common as gravel is still passing. Other problems may include perirenal hematomas (blood clots around the kidneys); hemorrhage; pancreatitis (inflammation of the pancreas ); damage to nearby organs and tissues (during ISWL); and obstruction by stone fragments. The most common complication is urinary tract infection, sometimes present prior to the procedure due to obstruction by stones. Prophylactic antibiotics are administered to treat infection. Other postprocedural complications sometimes associated with the administration of anesthetics include nausea, vomiting, and allergic reaction.

Health care team roles

Lithotripsy is performed by a urologist or urologic surgeon, sometimes in conjunction with a radiologist, and with assistance from nursing staff for patient monitoring and medication administration during the procedure. The procedure may also be performed by a uroradiologist. If ISWL requires general anesthesia or conscious sedation, an anesthesiologist and/or nurse anesthetist may need to be present for the procedure. Because ESWL uses x rays to locate the stones, a radiologic technologist may be required to assist with operating the x-ray equipment.

Resources

BOOKS

Tanagho, Emil, and Jack McAninch, eds. Smith's General Urology. 14th ed. Norwalk, CT: Appleton and Lange Publishers, 1995.

PERIODICALS

Portis, Andrew J. and Chandru P. Sundaram. "Diagnosis and Initial Management of Kidney Stones." American Family Physician 63, no. 7 (April 1, 2001): 1329-1338.

Shagam, Janet Yagoda. "Extracorporeal Shock Wave Lithotripsy." Radiologic Technology 72, no. 2 (November-December 2000): 145-163.

ORGANIZATIONS

American Urological Association. 1120 North Charles Street, Baltimore, MD 21201. 410-727-1100. 〈http://www.auanet.org〉.

National Kidney Foundation. 30 East 33rd Street, Suite 1100, New York, NY 10016. (800) 622-9010. 〈http://www.kidney.org〉.

Society of Urologic Nurses and Associates. East Holly Avenue, Box 56, Pitman, NJ 08071-0056. 609-256-2335. 〈http://suna.inurse.com/〉.

Lithotripsy

Definition

Lithotripsy is the use of high-energy shock waves to fragment and disintegrate kidney stones. The shock wave, created by using a high-voltage spark or an electromagnetic impulse, is focused on the stone. This shock wave shatters the stone and this allows the fragments to pass through the urinary system. Since the shock wave is generated outside the body, the procedure is termed extracorporeal shock wave lithotripsy, or ESWL.

Purpose

ESWL is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube which carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications if not removed.

Precautions

ESWL should not be considered for patients with severe skeletal deformities, patients weighing over 300 lbs (136 kg), patients with abdominal aortic aneurysms, or patients with uncontrollable bleeding disorders. Patients who are pregnant should not be treated with ESWL. Patients with cardiac pacemakers should be evaluated by a cardiologist familiar with ESWL. The cardiologist should be present during the ESWL procedure in the event the pacemaker needs to be overridden.

Description

Lithotripsy uses the technique of focused shock waves to fragment a stone in the kidney or the ureter. The patient is placed in a tub of water or in contact with a water-filled cushion, and a shock wave is created which is focused on the stone. The wave shatters and fragments the stone. The resulting debris, called gravel, then passes through the remainder of the ureter, through the bladder, and through the urethra during urination. There is minimal chance of damage to skin or internal organs because biologic tissues are resilient, not brittle, and because the the shock waves are not focused on them.

Preparation

Prior to the lithotripsy procedure, a complete physical examination is done, followed by tests to determine the number, location, and size of the stone or stones. A test called an intravenous pyelogram, or IVP, is used to locate the stones. An IVP involves injecting a dye into a vein in the arm. This dye, which shows up on x ray, travels through the bloodstream and is excreted by the kidneys. The dye then flows down the ureters and into the bladder. The dye surrounds the stones, and x rays are then used to evaluate the stones and the anatomy of the urinary system. (Some people are allergic to the dye material, so it cannot be used. For these people, focused sound waves, called ultrasound, can be used to see where the stones are located.) Blood tests are done to determine if any potential bleeding problems exist. For women of childbearing age, a pregnancy test is done to make sure the patient isn't pregnant; and elderly patients have an EKG done to make sure no potential heart problems exist. Some patients may have a stent placed prior to the lithotripsy procedure. A stent is a plastic tube placed in the ureter which allows the passage of gravel and urine after the ESWL procedure is completed.

KEY TERMS

Aneurysm— A dilation of the wall of an artery which causes a weak area prone to rupturing.

Bladder— Organ in which urine is stored prior to urination.

Bleeding disorder— Problems in the clotting mechanism of the blood.

Cardiologist— A physician who specializes in problems of the heart.

EKG— A tracing of the electrical activity of the heart.

ESWL (Extracorporeal shock wave lithotripsy)— The use of focused shock waves, generated outside the body, to fragment kidney stones.

Gravel— The debris which is formed from a fragmented kidney stone.

IVP (Intravenous pyelogram)— The use of a dye, injected into the veins, used to locate kidney stones. Also used to determine the anatomy of the urinary system.

Kidney stone— A hard mass that forms in the urinary tract and which can cause pain, bleeding, obstruction, or infection. Stones are primarily made up of calcium.

Stent— A plastic tube placed in the ureter prior to the ESWL procedure which facilitates the passage of gravel and urine

Ultrasound— Sound waves used to determine the internal structures of the body

Ureter— A tube which carries urine from the kidney to the bladder.

Urethra— A tube through which urine passes during urination.

Urologist— A physician who specializes in problems of the urinary system.

Aftercare

Most patients have a lot of blood in their urine after the ESWL procedure. This is normal and should clear after several days to a week or so. Lots of fluids should be taken to encourage the flushing of any gravel remaining in the urinary system. The patient should follow up with the urologist in about two weeks to make sure that everything is going as planned. If a stent has been inserted, it is normally removed at this time. Patients may return to work whenever they feel able.

Risks

Abdominal pain is not uncommon after ESWL, but it is usually not cause to worry. However, persistent or severe abdominal pain may imply unexpected internal injury. Colicky renal pain is very common as gravel is still passing. Other problems may include perirenal hematomas (blood clots near the kidneys) in 66% of the cases; nerve palsies; pancreatitis (inflammation of the pancreas); and obstruction by stone fragments. Occasionally, stones may not be completely fragmented during the first ESWL treatment and further ESWL procedures may be required.

Resources

ORGANIZATIONS

American Urological Association. 1120 North Charles St., Baltimore, MD 21201-5559. (410) 727-1100. 〈http://www.auanet.org/index_hi.cfm〉.

Lithotripsy

History

Lithotripsy and kidney stones

How it works

Lithotripsy, extracorporeal shock wave (ESWL), is the first noninvasive (not requiring surgical opening of the body) treatment for eliminating kidney stones by breaking them into sandlike particles, usually by means of high- pressure waves generated in water. The particles are then eliminated from the body during urination.

The ESWL machine, called a lithotripter, generates shock waves in a reservoir of water outside the body, then focuses them with a reflecting device so they pass through the water and into the body, striking individual stones. Waves are disturbances that travel from one point to another without transporting the material of the medium itself. Rather, there is successive compression and expansion of adjacent areas of the fluid. This can be visualized by imagining a cork bobbing up and down in water as a wave passes by. There is no net movement of water that can carry the cork along, only the passage of the disturbance itself. A shock wave is a compression wave (wave formed by compression of a fluid) that is fully developed, of very large amplitude, and travels through the medium at the speed of sound.

History

The concept of using shock waves to fragment stones had its origin in research done in Germany during the 1960s. Researchers found that the pitting of aircraft wings following supersonic flight was caused by collision of the airplane wing with rain drops. ESWL was introduced into the United States in 1984.

The use of sound waves to destroy kidney stones is based on the destructive force generated when a shock wave in fluid suddenly hits a substance that has different properties, such as a kidney stone. The shock waves pass efficiently through fluid mediums and can be focused so they strike small objects.

Lithotripsy and kidney stones

Kidney stones are formed from deposits of salt and mineral crystals on the inner surface of the kidneys or in the bladder. Often this occurs when the urine is persistently either acidic or alkaline. Most kidney stones contain large amounts of calcium. They vary in size and may remain inside the kidney or dislodge and pass into the ureter, the tube that carries urine from the kidney to the bladder.

If stones remain inside the kidney they may cause damage directly, or obstruct the flow of urine. Such an obstruction causes a buildup of pressure inside the kidney and interferes with the function of this organ, a condition called hydronephrosis. In turn, this can cause bacterial buildup in the stagnant urine, a condition called acute bacterial pyelonephritis.

Most kidney stones produce no symptoms and are only discovered during a routine x-ray examination, although some stones may cause blood in the urine. Usually, however, people discover they have kidney stones when they are stricken with terrible pain along their side or back, which occurs when the stone moves down the ureter.

Formerly, the two major forms of treatment were to wait for stones to pass through the bladder in the urine, or to remove it, usually by major abdominal surgery. Later, endoscopes—long light tubes used for looking inside the body—were used to locate stones, which were then grasped or crushed with basketlike devices on the end of tubes inserted under the guidance of endoscopes. But stone formation often recurs, and repeated surgery greatly increases the risk of permanent kidney damage or loss. More recently, ESWL has become the common method of treating kidney stones.

How it works

A lithotripter generates shock waves by means of electrical or spark discharges within a spherical or ellipsoidal reflector submerged in water. Some waves propagate directly away from the curved surface of the

reflector (primary shock waves). Others strike and bounce off the inner wall of the reflector (reflected shock waves).

In order to focus the shock waves so they pass into the body and strike kidney stones, physicians must first locate the stones by means of fluoroscopy or ultrasound.

During the treatment, there are a series of clicks that correspond to the shock waves passing through the water and body tissue to break up the stone. Treatment takes about one to two hours.

Early lithotripters required patients to be lowered into a water bath. Shock waves traveled through the water and into the body. The procedure restricted the positioning of the patient so that only stones in the upper urinary tract were accessible to shock waves.

More recent lithotripters do not require patients to be lowered into a bath or to lie on a bed of water. Rather, the water is located inside the shock wave generator under the table on which the patient lies. This keeps the patient and water apart, permitting doctors to position patients on the table more easily, and increases their ability to target and destroy stones.

ESWL does not damage the kidney, so the physician can repeat the procedure if necessary. Most patients can return home the same day of treatment.

In some patients, a stone may be able to be seen only after a narrow tube called a stent is placed in the ureter. The patient is first put under anesthesia. Then the physician inserts a thin, narrow light tube called a cystoscope into the urethra to help guide stent placement. The stent is removed after treatment.

Following treatment, the patient may feel an ache in the lower back, and may have some discomfort passing the remains of the stones. In addition, there is often blood in the urine.

The treatment is not recommended for everyone. For example, women who are pregnant and individuals who already have urinary tract infections should not undergo ESWL.

See also Bacteria; Fiber optics; Urology.

Marc Kusinitz