What is shock wave lithotripsy (SWL)?
Shock wave lithotripsy (SWL) is a treatment to remove kidney stones. It uses focused, high-energy shock waves to break kidney stones into tiny sand-like particles, sometimes called “stone dust”. Once they are small enough, the particles can pass out of your child’s body in their urine (pee).
The full name for shock wave lithotripsy is extracorporeal shock wave lithotripsy (ESWL). This means that the shock wave comes from outside the body and is directed towards your child’s kidney.
What are kidney stones?
Kidney stones are solid pieces of material that form from waste substances that are normally found in the urine. These substances include calcium and phosphorus. Normally the kidneys filter the substances, but if there is not enough liquid to flush them out, they can become highly concentrated and clump together.
A kidney stone can be small or large and may either stay in the kidney or pass into the urinary tract. A small stone can usually pass out of the body with little or no pain, but a larger stone may become stuck. This can block the flow of urine, causing severe pain, or damage the urinary tract, leading to blood in the urine.
Although they are not common, kidney stones can occur in infants, children and teenagers.
Causes of kidney stones
A child may develop kidney stones for a number of reasons, such as:
- problems with how the kidneys have developed
- a family history of kidney stones
- urinary tract infection(s)
- a metabolic disorder (a medical condition that prevents the body from digesting food properly)
- an unhealthy diet, for example drinking too little water or consuming too much sodium
How to prepare for shock wave lithotripsy
Before your child has shock wave lithotripsy, they will need to do certain tests. They will also need to stop taking certain medications before the treatment.
Tests
- Abdominal (tummy) X-ray (KUB): this takes place a maximum of four weeks before the treatment to confirm the size and location of the kidney stone(s)
- Urine culture and sensitivity test: this checks if your child needs any treatment for a urinary tract infection before the shock wave lithotripsy
- Blood work: this is only done if it's relevant for your child
Your child’s doctor may order other tests, for example a CT scan, if they believe they are necessary.
Your child’s health-care team will tell explain the exact tests your child will need before they have shock wave lithotripsy.
Medications
Ten days before the shock wave lithotripsy treatment, your child should stop taking acetylsalicylic acid (ASA), ibuprofen or any medications to treat blood conditions (such as anti-coagulants, anti-platelets or thinners).
If you have any questions about when your child should stop their medications, please speak with your child’s doctor or nurse.
What happens on the day of treatment?
General anaesthetic
Shock wave lithotripsy does not involve any surgery, but your child will still receive a general anaesthetic. The anaesthetic will make sure that your child sleeps through the treatment so that they do not feel any pain. It will also help your child stay still, which will improve the breaking down of the stones.
Use the following guidelines to make sure that your child’s stomach is empty before they receive the general anaesthetic.
- Midnight before your child’s treatment: Stop solid foods.
- Six hours before the treatment: Stop any formula or tube feeds.
- Four hours before the treatment: Stop giving breast milk, if relevant.
- Three hours before the treatment: Stop giving clear fluids such as apple juice or water.
It is very important that your child’s stomach is empty before the treatment. Any food or liquid in your child’s stomach while they are going to sleep under the anaesthetic can flow up to their mouth and pass down into their lungs. This is very dangerous for your child.
Treatment
During the procedure, your child will be on their back, either fully lying down or propped up at a 45-degree angle.
An X-ray machine will find the latest location of the kidney stone(s) to make sure the shock waves are accurate. Then, a special machine called a lithotripter will send shock waves to break down the stones and make them easier for your child to pass in their urine. The machine may be above your child or at their side.
How long does shock wave lithotripsy take?
Shock wave lithotripsy treatment generally takes 45 minutes to an hour. Your child will normally leave hospital on the same day as the treatment.
How many treatments will my child need?
Usually, one treatment will break down any kidney stones that have been found. Your child might need further treatments if their stones are large or not completely broken down.
What to expect after the treatment
Pain
It is normal for your child to experience pain in the area where they were treated, for example on their back and in their abdomen. Abdominal pain (cramping) can last for several days as the kidney stone particles pass out of their body.
Older children may describe their pain to you. In younger children, signs of pain include:
- wincing or guarding of the abdomen
- increased fussiness
- refusal to walk or trouble walking
- unusually quiet behaviour
You can help relieve your child’s pain by giving oral pain medications such as acetaminophen and encouraging your child to drink lots of water.
Nausea
It is common for a child to experience nausea and possible vomiting for the first 24 hours after a general anaesthetic and after shock wave lithotripsy. The nausea usually eases after a day or two.
Your child’s health-care team will give you instructions for managing any nausea at home after the treatment.
Bruising
Your child will likely have some bruising on their back for a few days.
Bleeding
The shock wave lithotripsy will likely cause some bleeding in the kidneys. This will lead to blood in your child’s urine for a few days after treatment.
Blocked ureter
Sometimes, the kidney stone particles can block the ureter as they pass out of the body. This may lead to a fever and cause increased pain. If your child’s ureter is blocked, your child’s surgeon may decide to insert a temporary stent (tube) to allow your child’s urine to bypass the blockage.
How to care for your child after shock wave lithotripsy
Follow the directions of your child’s doctor and nurse for caring for your child at home after the treatment. They will usually instruct that your child:
- drink plenty of fluids, especially water
- change their diet, if needed
- take medication to manage pain and nausea
- get plenty of rest
If your child is toilet trained, your child’s doctor or nurse may also instruct you to strain your child’s urine for several days and will explain how to do this.
Straining the urine will enable you to collect any stone particles so that they can be analyzed in a laboratory. Your child’s doctor will use the information about the make-up of the stone to monitor your child and make recommendations (such as changes in diet) to prevent the kidney stones from recurring.
When can my child return to normal activities?
Your child can return to their normal activities, including day care or school, a day or two after treatment once any pain or discomfort is under control. Check your child for any symptoms of pain to make sure that pain management is adequate.
Your child can have baths or showers as usual right after treatment.
Follow-up care
Your child’s doctor will usually schedule a follow-up appointment for your child about three to six months after the shock wave lithotripsy.
When to see a doctor after shock wave lithotripsy
Call your child’s doctor before then if your child:
- feels like they need to urinate (pee) but cannot do so
- has a fever measured at over 38.5°C (101.5°F)
- has nausea or vomiting that you cannot control with the medications you were given
- has excessive blood in their urine (for example, the urine is mainly red or has traces of blood throughout the day)
- is coughing repeatedly
- has shortness of breath or chest pain
- has uncontrollable abdominal or back pain
At SickKids
On the day of treatment, you will go directly to St. Michael’s Hospital at 30 Bond Street, Toronto. You and your child should arrive at St. Michael’s by 7.00am.
The Lithotripsy Unit is on the 5th Floor, Cardinal Carter Wing. The doctor and the team from The Hospital for Sick Children will meet you there.
For ease of access to the unit, enter St. Michael’s Hospital through the Victoria Street entrance. There is public parking on Victoria Street and Queen Street East.