Shock wave lithotripsy, or ESWL, is an outpatient procedure. It is usually performed under general anesthesia and takes about an hour. First, the kidney stone is located by x-rays. Then, the doctor directs high-intensity sound waves at the stone. The goal is to break the stone into tiny fragments (about the size of grains of sand) so they may then flush out of the body with the urine. The major advantage of ESWL is that it doesn't require incisions.
During ESWL, it is possible that some stones may not break or may break into large pieces that are difficult to pass. There is a limit to the number of shock waves that can be safely administered in a single treatment session.
While many ESWL patients are free from stones three months after the procedure, some require additional treatments.
A ureteral stent may be inserted at the time of treatment if your doctor is concerned that stone fragments will block your ureter. Stents are most commonly used for patients with ureteral stones, large stones (usually greater than 15 mm), particularly dense stones or those with a history of urinary tract infections. Stents are usually removed in the urologist's office, after x-rays indicate that there is no longer a risk of obstructing fragments.
ESWL may be a good option for those with:
- Stones that can be seen on an x-ray (are radio-opaque)
- Kidney stones less than 20 mm
- Ureteral stones less than 10 mm
ESWL may not be a good option for those with:
- Stones that are difficult to see on an x-ray
- Stones in the bottom part of the kidney (lower pole stones)
- Mid ureteral stones - Treating stones in the region of the ureter overlying the bony pelvis is not recommended because bone blocks shockwaves and makes it difficult to find the stone.
- Distal ureteral stones - These stones are often better treated by ureteroscopy
- Chronic infection - The only way to stop chronic infection associated with kidney stones is to completely remove the stones. ESWL tends to leave small fragments behind.
- Obstruction distal to stone - if the ureter is blocked by scarring or some other process, the stone fragments are unlikely to pass.
- Patients on blood thinners - ESWL treatment carries a risk of bleeding from the kidney.
- Obesity - Stones can be difficult to see in heavier patients. Most ESWL units cannot support a patient heavier than 350 pounds.
- Patients who require complete stone clearance - It may take up to three months for all fragments to clear after ESWL and that time period may be unacceptable for some patients.
Success rate of ESWL
As with any medical procedure, your doctor can't guarantee success. To give our patients the best chance at getting rid of stones, we select patients who are most likely to succeed before recommending ESWL.
Much of the research evaluating the effectiveness of ESWL was completed before CT scans were commonly used for stone disease. Therefore, it is difficult to compare older research with current research.
Older research - Using plain x-rays, patients with fragments less than 4 mm in size were generally considered to have had a successful treatment. Using this criteria, "successful treatment" occurs for 70 to 80 percent of ureteral stones and 60 to 80 percent of kidney stones.
Current research - A more recent study used CT scans to look for fragments in patients with lower pole stones less than 1 cm who had undergone ESWL treatment. Researchers found that less than 30 percent of patients had completely successful treatment.
How you'll feel after ESWL
Most patients experience discomfort for a day or two after ESWL. Generally, the discomfort is at its worst the evening after surgery and then gradually lessens. It is normal to see small amounts of blood in the urine for up to a month after surgery. As with any procedure requiring general anesthesia, many patients also find that they are more tired for up to a month after the procedure.
While most patients who undergo ESWL don't have complications, it's important to report any of the following to your doctor:
- Increasing pain - May be sign of an obstruction caused by kidney stones or kidney injury
- Heavy bleeding or blood clots - May be a sign of kidney injury
- Fever - May indicate a serious kidney infection
- Feeling unwell - It is normal to feel tired but it is not normal to feel sick
Follow-up after ESWL
If you have a stent, your urologist will want to see you one week after the procedure. An x-ray will be taken to see if the stone has cleared. If so, the stent can be removed. If the stone fragments haven't cleared, x-rays may be repeated every one to two weeks.
If you don't have a stent, an x-ray will be performed one month after the procedure to see if the stone fragments have cleared.
In either case, if large stone fragments remain, further treatment with ESWL or ureteroscopy may be recommended.
Contact Kidney Stone InstituteA doctor's referral is not required to make an appointment.
Monday through Friday, 8 am to 4:30 pm
Outside of these hours, you can call us and speak with a registered nurse who will review your symptoms and make recommendations to help you get appropriate care.