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Extracorporeal shock wave lithotripsy (SWL) is a technique that uses sound waves (ultrasound) to break up simple stones in the kidney or upper urinary tract. ("Extracorporeal" means "outside the body," and "lithotripsy" means stone-breaking.) SWL is not used for cystine stones. The procedure generally does not work for stones larger than 3 centimeters in diameter (which is slightly over an inch). There are several variations of SWL. The following is a typical procedure:
- SWL procedures can often be done on an outpatient basis.
- The patient is positioned in a water bath. (In some procedures the patient lies on a soft cushion.)
- The procedure uses ultrasound to generate shock waves that travel through the skin and body tissues until they hit the dense stones. (The doctor pinpoints the stone during treatment by using x-rays or ultrasound.)
- The shock waves crush the stones into tiny sand-like pieces that usually pass easily through the urinary tract.
The shattered stone fragments may cause discomfort as they pass through the urinary tract. If so, the doctor may insert a small tube called a stent through the bladder into the ureter to help the fragments pass. This practice, however, does not usually speed up passage of the stones and is not used routinely.
SWL has a 50 - 90% success rate, depending on the location of the stone and the surgeon's technique and experience. Recovery time is short. Most people can resume normal activities in a few days.
SWL is generally safe, and has few complications. If they do occur, complications may include:
- Blood in the urine, the most common complication, may last for a few days after treatment. To reduce the chances of bleeding, doctors usually tell patients to avoid taking aspirin and other NSAIDs, which can promote bleeding, for 7 - 10 days before the treatment.
- Bruising and minor discomfort due to the shock waves are common in the back or abdomen.
- Sometimes the stone does not completely break up with one treatment, and additional treatments may be required. Inability to pass stone fragments may also be a particular problem in patients who have cysts or other kidney problems.
- SWL does increase the risk of damage to the kidneys.
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Review Date: 06/08/2010
Reviewed By: Reviewed by: Harvey Simon, MD, Editor-in-Chief, Associate Professor
of Medicine, Harvard Medical School; Physician, Massachusetts
General Hospital. Also reviewed by David Zieve, MD, MHA, Medical
Director, A.D.A.M., Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
