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.

  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.

   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.

   Resources:

Books

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

Organizations

• American Urological Association. 1000 Corporate Boulevard, Linthicum, MD 21090. (866)-RING AUA. http://www.auanet.org & http://www.urologyhealth.org