Shock wave lithotripsy (ESWL)
Focused shock waves from a machine outside your body travel through the skin to break a kidney or ureter stone into sand-sized pieces that you then pass in your urine. There are no cuts and no scopes.
Also called ESWL, SWL, extracorporeal shock wave lithotripsy, lithotripsy, litho, lithotripter, shock wave therapy for kidney stones, sound waves to break a kidney stone
- Where
- Hospital or outpatient lithotripsy unit
- Anesthesia
- IV sedation (sleepy and comfortable) or light general anesthesia
- Time in the room
- About 45 to 60 minutes of treatment
- Hospital stay
- Same day
- Back to normal
- 1 to 3 days, though passing pieces can cause cramps for a few weeks
- Back to work
- 1 to 2 days
Overview
Shock wave lithotripsy, also called ESWL or SWL, breaks kidney and ureter stones from outside the body. You lie on a padded table while a machine called a lithotripter sends focused pulses of sound energy, called shock waves, through a water-filled cushion pressed against your side. The waves pass through skin and muscle and meet at the stone, which cracks and crumbles into sand-like pieces. You then pass those pieces in your urine over the following days to weeks.
There are no cuts and no scopes, and most people go home within an hour or two. SWL has been a mainstay of stone treatment since the 1980s. The tradeoff is that it relies on your body to pass the pieces, and it is less likely than ureteroscopy to clear a stone in one session. Some people need a second session or a different procedure.
SWL works best for stones under about 1 to 2 centimeters in the kidney or upper ureter that are not too hard. It works less well for very dense stones, stones in the lowest part of the kidney, larger stones, and in people with more body tissue between the skin and the stone. Your CT scan helps predict whether SWL is a good match for you.
The parts of your body involved
Your kidneys sit high in the back of your belly, partly under the lower ribs. Urine collects in small cup-shaped chambers called calyces, drains into a funnel called the renal pelvis, and then flows down the ureter (the tube from kidney to bladder) to the bladder. Shock waves travel easily through water and soft tissue, which is why the machine uses a water cushion against your skin. Bone blocks them, so stones hidden behind a rib or the pelvic bones are harder to treat. After SWL, the pieces must travel down the ureter on their own. Pieces in the upper and middle kidney drain downhill easily. Pieces in the lowest calyces must travel uphill and are more likely to stay behind.
- Kidney
Makes urine. It moves a little with each breath, so the machine re-checks the stone's position during treatment.
- Upper and middle calyces
Stones here clear well after SWL because pieces drain downhill.
- Lower pole calyces
The lowest cups drain uphill, so pieces from stones here clear less reliably.
- Ureter
The narrow tube the pieces must pass through. Cramping pain happens when a piece moves through it.
- Skin and back muscles
The shock waves pass through these on the way in. They may bruise slightly. The more tissue between skin and stone, the weaker the waves are by the time they arrive.
Why it’s done
SWL is offered when a stone needs treatment and is a good match for shock waves. Many people choose it because it avoids a scope, usually avoids a stent, and is done under light sedation.
- A kidney stone up to about 2 centimeters
Results are best for stones under 1 centimeter in the upper or middle kidney. For lower pole stones, SWL is usually reserved for stones under about 1 centimeter.
- A stone in the upper ureter
Stones up to about 1 centimeter in the upper ureter can often be treated with SWL.
- Avoiding a scope and stent
SWL needs no scope through the urethra, and a stent is rarely needed. Most people are back to normal in a day or two.
- A stone that is not passing
Stones that have not moved after several weeks, or that keep causing pain, can be broken so the pieces pass more easily.
- A kidney stone causing trouble
Stones that cause bleeding, repeated infections or pain, or that keep growing on scans.
Other options
- Waiting, with medicine to help the stone pass
Many ureter stones up to about 10 millimeters pass within 4 to 6 weeks if pain is controlled and there is no infection. Tamsulosin can help, especially for stones in the lower ureter.
- Ureteroscopy with laser
A thin scope passed up from the bladder with a laser to break the stone. It clears more stones in one session than SWL and works on any stone hardness, but it needs anesthesia and often a stent for several days.
- Percutaneous nephrolithotomy (PCNL)
Keyhole surgery through the back, best for kidney stones larger than 2 centimeters and larger lower pole stones.
- Watching a kidney stone that causes no trouble
Small kidney stones with no pain, blockage or infection can often be watched with periodic scans while you work on prevention.
Getting ready
Tick items off as you go. Your checklist is saved on this device only.
Weeks before
The week before
The day before
The morning of
In the operating room, step by step
Press play or pick a step. Each drawing shows what your surgeon is doing at that moment. Your team may do some steps differently.
1. Lying on the treatment table
You lie on your back on a padded table with the stone side positioned over the treatment head. For some stones low in the ureter, you lie on your front instead so the waves avoid the pelvic bones.
After the operation
Right afterward
- Recovery
You rest for 30 to 60 minutes while the sedation wears off. Most people feel surprisingly well.
- Your first urination
Pink or red urine is expected. Some centers ask you to urinate before you leave.
- Strainer and medicines
You go home with a strainer, a pain medicine plan, and sometimes tamsulosin to help pieces pass.
- Getting home
An adult must drive you. Do not drive, sign important papers or drink alcohol for 24 hours.
At home
- Blood in the urine
Pink to red urine for 1 to 3 days is normal. Thick clots or urine like ketchup need a call.
- Pain while pieces pass
Cramping pain in your side, belly or groin can come and go as pieces move. Anti-inflammatory pain pills such as ibuprofen work well for stone pain if your kidneys and stomach allow them. A heating pad helps.
- Bruising and soreness
The skin where the cushion pressed may be bruised or tender for a few days.
- Drink and keep moving
Drink enough to keep urine pale, for most people about 2.5 to 3 liters a day. Walking helps pieces move down.
- Straining your urine
Urinate through the strainer and save pieces in a clean container for the lab, for as long as your team asks.
- Tamsulosin
If prescribed, it can cause lightheadedness when you stand up quickly and, in men, less fluid with ejaculation. Both stop when the medicine stops.
- Driving and work
No driving for 24 hours. Most people return to work in 1 to 2 days.
- Blood thinners
Restart only when your team tells you, often a few days after treatment.
- Preventing the next stone
Drink enough to make about 2.5 liters of urine a day, keep sodium to about 2,300 milligrams a day or less, eat normal calcium from food, limit meat, poultry and seafood, eat plenty of fruits and vegetables, and avoid sugar-sweetened drinks. Your stone analysis may add specific steps, such as limiting high-oxalate foods. People with repeat stones are often offered a 24-hour urine test.
Recovery timeline
- Day 0Home within hours
Pink urine and a mild ache are expected. Rest and drink.
- Days 1 to 3Back to routine
Most people return to normal activity and work. Bruising on the back fades.
- Weeks 1 to 4Pieces pass
You may feel cramps and see grit in the strainer. Many pieces pass without notice.
- Weeks 2 to 6Follow-up imaging
An X-ray, ultrasound or CT shows how much stone is left and whether the kidney is draining.
- Up to 3 monthsLast pieces clear
Remaining small pieces often pass over the next weeks. If a sizeable piece remains, a second SWL session or ureteroscopy may be offered.
- Months 1 to 3Prevention plan
Stone analysis and, for some people, a 24-hour urine test guide diet changes or medicines.
- Long termStaying stone-free
Without prevention, stones often come back, with up to half of people forming another within 5 to 10 years.
What it feels like
For most people SWL is the gentlest stone treatment in the moment. The harder part, if any, is the days afterward while the pieces pass.
Before treatment
Many people are not sure what shock waves will feel like, or expect a laser. Some feel uneasy about lying still on a machine.
What helpsAsk the team to describe the sounds and sensations. Knowing the snapping is expected makes it easier.
During treatment
With sedation, most people are drowsy and remember little. Those more awake describe a flick or snap against the back, like a rubber band, in a steady rhythm, with a clicking sound.
What helpsTell the team if it becomes painful. They can adjust the power or give more medicine.
Right after
A bruised ache on the back, tiredness from the sedation, and red urine that can look alarming.
What helpsDrink steadily. The color usually lightens within a day or two.
Passing the pieces
Cramping waves of pain in the side or groin, sometimes with nausea, as a piece moves. Then relief, and sometimes a gritty feeling or a tiny stone in the strainer.
What helpsTake your pain medicine early in an attack. Heat, walking and fluids help. Call if the pain does not settle with your medicines.
Waiting for the follow-up X-ray
Uncertainty about whether it worked, especially if you have not seen any pieces.
What helpsMany pieces pass unseen. The follow-up scan gives the real answer.
If you need another session
Disappointment and frustration are common, especially after taking time off.
What helpsAsk whether a repeat SWL or switching to ureteroscopy gives the better chance for your stone.
How well it works
Success means the stone is gone or only very small pieces remain, and the kidney drains normally. SWL is most successful for small, less dense stones in the upper or middle kidney or upper ureter. In a large UK trial of ureter stones (TISU), people treated first with SWL needed more additional treatments than those treated with ureteroscopy.
- Follow-up imaging
An X-ray, ultrasound or CT a few weeks after treatment shows what is left. Pieces smaller than about 4 millimeters often pass or stay quiet, and are watched.
- Stone analysis
Pieces caught in the strainer tell the lab what the stone is made of, which guides prevention.
- A second treatment, if needed
Sizeable leftover pieces may be treated with another SWL session, usually a few weeks later, or with ureteroscopy.
- Prevention
People with repeat stones or a higher risk are offered a 24-hour urine test and a tailored plan.
Risks
Every operation has risks. These are the ones people ask about most, with honest odds where good numbers exist. Your surgeon’s own results matter more than averages.
Common
Pink or red urine for 1 to 3 days.
Where the cushion pressed. Fades within days.
Comes and goes over days to weeks. Usually controlled with pills.
More likely with larger, denser or lower pole kidney stones, and with more tissue between the skin and the stone.
Less common
Usually responds to antibiotics. Treating any urine infection before SWL lowers the risk.
Called steinstrasse, or stone street. More likely after stones larger than 2 centimeters. It often passes on its own but may need ureteroscopy or a drainage tube.
Most common with lower pole stones. They may be watched or treated later.
Usually brief and harmless. The team adjusts the shock timing.
Rare
A collection of blood (hematoma) around the kidney that causes pain and may need a hospital stay. More likely with high blood pressure or blood thinners.
Infection that spreads to the blood and needs hospital care.
Very rare bruising of the bowel, spleen, liver or pancreas.
Call your care team or go to the emergency room if
- Fever of 101°F (38.3°C) or higher, or shaking chills
- Pain in your side, belly or groin that your prescribed medicines do not control
- Pain with dizziness, fainting or a racing heartbeat
- Vomiting that keeps you from holding down fluids or medicines
- You cannot urinate, or you pass very little urine
- Thick clots or urine like ketchup that does not lighten after drinking more
- Chest pain or shortness of breath (call 911)
Questions to ask your surgeon
- How big and how dense is my stone, and how likely is SWL to clear it in one session?
- Is my stone in a good position for SWL, or is it in the lower pole or over bone?
- Would ureteroscopy give me a better chance of being stone-free?
- Will I have sedation or general anesthesia?
- Will I need a stent?
- When should I stop my aspirin or blood thinner, and when can I restart?
- Should I take tamsulosin afterward?
- How long should I strain my urine?
- When is my follow-up imaging, and what kind?
- If pieces remain, would you repeat SWL or switch to another treatment?
Words you may hear
- Lithotripsy
- Breaking a stone. Lithotripsy means stone crushing.
- Shock wave
- A short, powerful pulse of sound energy that can crack a stone.
- Lithotripter
- The machine that makes and focuses the shock waves.
- Calyx
- One of the cup-shaped chambers inside the kidney where urine collects. Plural: calyces.
- Lower pole
- The lowest part of the kidney. Pieces here have to travel uphill to drain.
- Stone density
- How hard a stone is likely to be, estimated on CT in units called Hounsfield units. Denser stones break less well with SWL.
- Skin-to-stone distance
- How far the stone sits from your skin on CT. Longer distances weaken the shock waves.
- Renal colic
- Cramping pain, often in waves, caused by a stone or piece moving through the ureter.
- Steinstrasse
- German for stone street: a line of stone pieces stacked up and blocking the ureter.
- Tamsulosin
- A pill that relaxes the muscle of the lower ureter, helping some stones and pieces pass.
- Hematoma
- A collection of blood outside a blood vessel, here around the kidney.
- Fluoroscopy
- Live X-ray pictures used to find and target the stone.
Common questions
Does it hurt?
With sedation, most people feel only a tapping or snapping on the back. Afterward, the back may feel bruised, and passing pieces can cause cramps for a few days to weeks.
Is shock wave lithotripsy a laser?
No. It uses sound energy from outside the body. Lasers are used through a scope during ureteroscopy or PCNL.
Will I need a stent?
Usually not. Guidelines advise against routine stents before SWL. A stent may be placed for very large stones, a single kidney, or if pieces block the ureter afterward.
Why might SWL not be the best choice for my stone?
SWL works less well for stones larger than 2 centimeters, very dense stones such as cystine or some calcium oxalate stones, stones in the lowest part of the kidney, and when there is a lot of tissue between the skin and the stone. Your CT scan helps your surgeon judge this.
Who should not have SWL?
It is not done during pregnancy, with an untreated urine infection, with a bleeding problem or blood thinners that cannot be stopped, with a blockage below the stone, or with a bulging artery (aneurysm) near the stone.
How long does it take to pass the pieces?
Most pass within a few weeks. Some take up to 3 months. Drinking well and staying active help.
Does SWL harm the kidney in the long run?
SWL causes some bruising inside the kidney that heals over weeks. Large studies have not shown clear long-term harm to kidney function for most people. Your team uses the lowest effective number of shocks.
What can I do to avoid another stone?
Drink enough to make about 2.5 liters of urine a day. Cut back on salt and meat, keep normal calcium from food, eat plenty of fruits and vegetables, and skip sugary drinks. Your stone analysis may add specific advice.
Sources this page draws on
- American Urological Association and Endourological Society, Surgical Management of Stones: AUA/Endourological Society Guideline (2016)
- European Association of Urology, EAU Guidelines on Urolithiasis
- The Lancet, Shockwave lithotripsy versus ureteroscopic treatment as therapeutic interventions for stones of the ureter (TISU): a multicentre randomised controlled non-inferiority trial (2022)
- American Urological Association, Medical Management of Kidney Stones: AUA Guideline (2014)
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Kidney Stones
- Urology Care Foundation, Kidney Stones
Written November 2026. This page explains what usually happens. It is not medical advice and does not replace a conversation with your own surgeon, whose plan for you comes first.