Overview of Extracorporeal Shockwave Lithotripsy
Extracorporeal shockwave lithotripsy (ESWL) is a method developed for addressing urinary stone issues without surgery. It uses shockwaves to break kidney and ureteral stones (stones in the tube that carries urine from the kidney to the bladder) into pieces small enough to pass out of the body naturally. Introduced in the 1980s, ESWL continues to be a key procedure for treating urinary stones (also known as urolithiasis), providing a safer and less invasive option compared to traditional surgery. With its ability to break up stones, low risk level, and relatively quick recovery period, ESWL plays a vital role in modern urology, the branch of medicine dealing with the urinary system.
Urinary stones are a major issue worldwide, affecting many people and incurring significant costs to the healthcare system. The number of people with urinary stones has risen from 3.8% in 1970 to 8.8% in 2010, and reached 11% by 2022 in the US alone. This has led to healthcare costs of around $3.8 billion per year and is increasing. Each year, around a million individuals in the US visit the emergency room for severe kidney pain or problems related to kidney stones, with about 20% of these cases requiring hospital admission.
However, ESWL has helped to improve patient outcomes and reduce the financial pressure on the healthcare system. It reduces the need for more invasive surgeries and decreases hospital stays, making it a cost-effective solution for treating urinary stones. As such, it is an essential tool in maintaining the health of patients while managing healthcare system costs.
Anatomy and Physiology of Extracorporeal Shockwave Lithotripsy
Stones can form at any point in the urinary system, from the kidneys to the tube where urine leaves the body, known as the urethra. These stones often start in parts of the kidney called the renal calyces, but they can then block other important locations like the ureteropelvic junction (UPJ), the ureter, or the ureterovesical junction (UVJ). The process that leads to stone formation is quite complex and involves many factors.
Most kidney stones start as what are called Randall plaques deep inside the kidney. These plaques are collections of calcium phosphate that form in a part of the kidney called the renal papilla, usually around the outlet of a structure called the collecting duct. In individuals who are prone to forming calcium oxalate stones, this buildup of calcium tends to occur in a layer called the basement membrane of what’s known as the loops of Henle.
Randall plaques start underneath the renal urothelium, which is the multi-layered lining of the urinary system, and gradually grow larger until parts of the plaque come into direct contact with urine inside the kidney. When these plaques touch urine, crystals begin to form on what’s called the nidus, and these keep accumulating thanks to processes of aggregation and epitaxy.
Calcium oxalate stones are the most common type of urinary stones, and they tend to form when the urinary pH is under 7.2. This is a condition shared with uric acid stones, which are usually caused by acidic urine. Calcium phosphate stones usually form in urine with a more alkaline pH.
The most frequently observed kidney stones are those containing calcium. Next to them are uric acid stones and struvite stones which are associated with infection. Cystine stones are quite rare – they only account for 1% to 2% of all urinary stones.
Why do People Need Extracorporeal Shockwave Lithotripsy
If you’re experiencing extreme kidney pain (renal colic) for over 72 hours, along with symptoms like nausea or vomiting, or if there’s an infection or your kidney function is declining, surgery might be needed. This particular type of surgery is commonly used to treat urolithiasis, which is a condition where stones form in the urinary system. Typically, those stones can pass naturally with time, but sometimes, immediate temporary relief comes from a procedure that inserts a double J stent to alleviate any blockage. But in the long run, to remove the stones, an elective surgery (a surgery scheduled in advance because it is not an emergency) might be required.
Extracorporeal shock wave lithotripsy (ESWL) is one option for this type of surgery. It’s usually reserved for kidney stones or stones in the tubes leading to your bladder (ureters). It can be used in urgent situations, like when you’re hit with sudden, severe kidney pain because of a stone in your ureter. ESWL is often compared to a procedure called a ureteroscopy, which removes stones from your ureter. While ureteroscopy is more invasive than ESWL, it tends to have a higher initial success rate, particularly for stones located in the lower part of the ureter.
There are several reasons why you might need surgery for urolithiasis:
- If the stone in the ureter hasn’t moved or passed after 1 to 1.5 months
- If there’s no urine output or very little urine output (which would call for a double J stent)
- If the stone is very large (over 10 mm)
- In the case of an infected, blocked kidney (also requiring a double J stent)
- In the case of a solitary kidney (only one functioning kidney) that is blocked (requiring a double J stent)
- If the patient prefers a surgical intervention
- If the symptoms like pain, nausea, and vomiting persist or are severe
- If both ureters are blocked at the same time (also needing a double J stent)
- If there is an infection in the urinary tract (a condition requiring double J stent placement)
- In the case of urinary sepsis (a severe infection that has spread through the bloodstream to the urinary tract, requiring double J stent placement)
- If kidney function is declining or kidney tissue is being lost
ESWL is a non-invasive surgery option that uses shock waves to break up the stones, which can then be passed naturally through urine. Although it’s the only non-invasive option and it’s generally safe, deciding between ESWL and more invasive methods would depend on features of the stone, such as its size, location, composition, and patient choice.
ESWL is generally considered a good first treatment for kidney and ureter stones that are less than 2 cm in size. However, it tends to be less successful on stones larger than 2 cm. It can be performed under local anesthesia or sedation, which makes it a possible choice even for people who can’t undergo general anesthesia.
If the stone is very large (over 2 cm), placing a ureteric stent before the ESWL procedure can help reduce the risk of blockage or intense pain in the ureter due to stone fragments after the procedure. The probability of success starts to decrease when the stone is in a part of the kidney that is lowest and furthest from the exit (lower pole), measures more than a cm, or is extremely dense. Even though these stones can be successfully disintegrated, clearing them from the kidney becomes an issue due to the positioning.
Doctors consider several factors when deciding on the optimal treatment for urinary stones such as size, body structure, weight and personal choice. For instance, if a patient is obese or if the distance from the skin to the stone in the kidney is more than 10 cm, the stone might be more challenging to remove with ESWL. Equally, certain kidney or skeletal conditions might require more consideration prior to deciding on using ESWL.
While ESWL is a popular choice due to its non-invasiveness, another procedure known as ureteroscopy is an available alternative. This procedure is more invasive, but it has higher initial success rates and lower rates of needing to be done again. It’s especially effective when treating certain types of stones. However, when repeated ESWL treatments are taken into account, the overall success rates between ureteroscopy and ESWL become comparable.
When a Person Should Avoid Extracorporeal Shockwave Lithotripsy
ESWL (Extracorporeal Shock Wave Lithotripsy), a procedure for breaking up kidney stones, can sometimes be harmful to certain people. For example, ESWL isn’t recommended for pregnant women because it has been linked to several issues including low birth weight, miscarriages, gestational diabetes, increased exposure to ionizing radiation, and displacement of the placenta, the organ that provides nourishment to the fetus during pregnancy.
People with a severe abdominal aortic aneurysm, a condition where the large blood vessel that supplies blood to the abdomen, pelvis, and legs becomes abnormally large or balloons outward, should also exercise caution with ESWL. The procedure can seriously increase their risk of bleeding and rupture of the blood vessel. If you have this condition, your doctor will discuss other ways to treat your kidney stones in order to avoid these risks.
If you have a condition that makes it difficult for your blood to clot or you’re taking medications that reduce clotting (like blood thinners), you are at an increased risk of bleeding after ESWL. It’s recommended to stop these medications before the procedure. But, if it is unsafe to do so, your doctor may recommend a different kind of procedure.
Severe or uncontrolled high blood pressure is another factor that makes ESWL risky as it can increase the chances of bleeding and developing blood clots (hematomas) around the kidneys. If you have high blood pressure, careful health checks and management of your blood pressure are necessary before undergoing ESWL.
Patients with infections in their kidney stones, untreated urinary tract infections (UTIs), or bacteriuria (bacteria in urine) are more likely to develop kidney infection or systemic infections following ESWL. Furthermore, blockages in the urinary tract located distal to (or farther away from the body’s center than) the stone being treated is a condition that makes ESWL not suitable. If, for some reason, the stone can’t be easily seen, even with special x-ray techniques like intravenous or retrograde pyelography, other imaging techniques or treatment methods may be necessary.
Equipment used for Extracorporeal Shockwave Lithotripsy
Extracorporeal shock wave lithotripsy (ESWL) is a treatment that uses strong vibrations, produced by a generator, usually under water, to break apart kidney stones. These vibration waves are directed to the exact spot where the stone is located. The energy from these waves remains harmless as they pass through water and body tissues, but once they reach the stone, they become concentrated and intensify. This energy is then converted into motion energy, which crushes the stone into smaller pieces that can be easily passed out of the body.
Several mechanisms help break the stone apart. One such method is cavitation, which involves forming small gas bubbles around the stone due to the attraction of the strong vibration wave. When these bubbles burst, they release a small jet of energy-rich fluid that hits the surface of the stone. Another method is cleavage, wherein the stone is cut up either parallel or perpendicular to the direction of the vibration wave, leading to the development of tiny cracks inside the stone that eventually join up and break the stone apart. In addition to these, there are other mechanisms too such as fatigue, shear stress, spall fracturing, squeezing, and superfocusing, all of which contribute to breaking the stone into smaller pieces.
The machines used for ESWL are called lithotripters and are mainly of three types: electrohydraulic, electromagnetic, and piezoelectric. All these machines are equally effective in breaking down stones. The electrohydraulic type uses an electrical discharge from an underwater spark plug to generate the vibration wave. While this type is quite effective, it goes through significant pressure variations and requires frequent replacement of the spark plug electrode. A recent advancement is the use of electroconductive materials to improve energy efficiency and reduce pressure variations. Factors affecting successful ESWL therapy include the stone’s chemical composition, density, size, and distance from the skin.
On the other hand, electromagnetic generators produce vibrations within a cylindrical tube by activating a metallic membrane using a powerful magnet. While these machines are known for their durability and cause relatively less discomfort to the patient, the treatment area is quite small, requiring precise targeting. Piezoelectric generators, however, use unique ceramic crystals that vibrate to generate the vibration wave. Although highly accurate and durable, these machines have a limited energy delivery, thereby limiting their capacity to break down larger stones. To counteract this limitation, a double layer of piezoelectric material is often used.
In addition to the ESWL machine, other necessary equipment includes an ultrasound or fluoroscopy for stone localization and precise targeting, a specialized table for patient comfort and accessibility to the machine, and a coupling system to enhance shock wave delivery and minimize energy loss.
Who is needed to perform Extracorporeal Shockwave Lithotripsy?
A urologist (a doctor that specializes in urinary healthcare), an assistant, a certified technician, and an anesthetist (a medical specialist who makes sure you don’t feel pain during procedures) work together in a procedure known as ESWL. This team of healthcare professionals each has a specific role during the procedure.
The anesthetist is there to make sure you have enough anesthesia (medicine to numb you) and painkillers during the procedure. Their main role is to help you feel as comfortable as possible so that you don’t move because of pain, which may affect the procedure’s success.
The certified technician is responsible for preparing and managing the device used for breaking down kidney stones, known as the lithotripsy equipment.
The urologist, also called a “urinary doctor,” plays an important role throughout the process. They locate and target the kidney stone or stones at the start of the procedure, ensuring that they break them down effectively. The kidney stones can break into smaller pieces, move, or may even appear as multiple stones that need to be targeted individually. As such, the urologist must be there throughout the procedure. They will plan the treatment and make the necessary adjustments based on what they find during the procedure.
Preparing for Extracorporeal Shockwave Lithotripsy
Before starting a procedure called extracorporeal shock wave lithotripsy (ESWL), which is used to break up kidney stones, it’s important to fully evaluate a patient. This check-up includes getting a detailed medical history and carrying out a thorough physical examination. The goal is to spot any reasons that might make ESWL a poor choice to treat a patient, pinpoint exactly where the stones are, assess any possible complications from having kidney stones, and understand any health issues that might affect how well ESWL works. This careful approach aims to ensure the patient’s safety and get the best results from the treatment.
There are several key tests doctors use to help them decide whether to proceed with ESWL therapy. Firstly, they commonly use an x-ray (KUB) or ultrasound of the kidneys, ureters (the tubes that carry urine from the kidneys to the bladder), and bladder as the first screening test. These scans can detect kidney stones larger than 5 mm that are not made of calcium and can pinpoint any blockages or buildup of urine in the kidney. An x-ray provides a more detailed picture of the kidney stone and helps doctors properly target the stone during ESWL therapy.
A CT scan, which takes many x-ray pictures from different angles to produce detailed images of the inside of the body, is the best way to locate the kidney stone and spot any related complications. This scan also gives doctors valuable information about the layout of the kidney, the density of the stone, and other factors that could impact treatment. Additionally, doctors typically perform other tests such as looking at a sample of urine, a urine culture, and a white blood cell count to help rule out infections and to get a better understanding of the patient’s overall health. These tests provide important information about the health of the urinary tract which can help guide treatment decisions. Before performing ESWL, a coagulation profile, a test that measures how well blood clots, is conducted to identify any undesired bleeding during the procedure.
It’s also important to have detailed discussions with the patient and their family to explain the treatment options and their potential benefits and risks. Patients should fully understand what the procedure entails, what the possible outcomes are, and what risks are associated with it. As part of this process, patients are informed about the possibility of needing a second ESWL treatment. This should be compared to other options, like ureteroscopy, to provide a full overview of the choices available.
ESWL has several benefits when compared to ureteroscopy. It’s less invasive, has a lower risk of complications, and is safer overall. It’s the best choice for brittle kidney stones (as revealed by a CT scan), and is quicker and more predictable in terms of surgical time. ESWL works well for kidney and ureteral stones, is usually done using just intravenous sedation, and does not typically require the insertion of a double J stent (a small tube inserted into the ureter to allow free flow of urine). This makes it a preferred choice for patients who wish to avoid more invasive surgeries and for those who are frail, pediatric, or older. Alongside these benefits, ESWL is much more cost-effective than endourological procedures (procedures involving the urinary tract), even though additional procedures are often required.
However, ESWL also has some drawbacks. For instance, it might not work well for stones that are radio-opaque (do not show up on x-ray), resistant to ESWL, very hard, or radiodense (show up well on x-ray). It’s less effective for larger stones and may not provide the best results in patients with a certain body weight or if multiple stones are scattered and need to be targeted separately. If kidney stones are in the lower part of the kidney, they can be broken up with ESWL therapy, but usually do not pass out of the body as easily, resulting in slower stone clearance rates. Moreover, although the success rate is similar to that of ureteroscopy, achieving this usually requires more than one ESWL treatment and takes longer.
When kidney stones are in the lower part of the ureter, a procedure called ureteroscopy is often the best treatment. If ESWL has been attempted twice and has failed, another treatment approach like ureteroscopy might be needed. It’s also important to note that ESWL is not recommended for patients who are pregnant, have uncontrolled or severe high blood pressure, have a ballooning of the aorta in the path of the targeted area, or have untreated bleeding disorders.
How is Extracorporeal Shockwave Lithotripsy performed
Extracorporeal Shock Wave Lithotripsy (ESWL) is a medical procedure that was first introduced in Germany in 1980 and then approved in the US in 1984. This treatment uses shockwaves to break down kidney stones and stones in the urinary tract. Over many years, it has become one of the main methods used to treat kidney stones because it is less invasive and has a very low risk of complications.
ESWL works by applying shockwaves to the patient’s body. The machines used in this procedure need to be in direct contact with the patient, usually through a water-filled balloon filled with a special type of gel that helps transmit the shockwaves. The aim is to avoid any loss of pressure during the treatment because air bubbles or gaps can reduce the efficiency of the shockwaves, leading to a significant loss of power.
Even a small amount of air covering just 2% of the head of the treatment machine can decrease the efficiency of the shockwaves by up to 40%. This is why it is so important to apply the gel correctly to avoid any loss of energy, which can affect the success of the ESWL treatment.
One way to efficiently apply the gel and reduce air bubbles or gaps is by putting a generous amount of the gel directly from the container onto the treatment head, allowing it to spread when it comes into contact with the patient’s skin. This approach helps improve the transmission of the shockwaves. Avoid applying the gel to both the machine and the patient’s skin, or using smaller gel bottles or gloved hands, as these methods can introduce more air bubbles and gaps.
Once the machine is properly in contact with the patient’s skin, it is important to maintain this contact throughout the procedure, as breaking it can cut the energy of the shockwaves by half. This continuity ensures the shockwaves are effectively delivered.
The stones that need to be targeted are typically located through a process called fluoroscopy. In the past, this process involved using two machines placed at a 90-degree angle. The center of the location of each machine indicated the best point of focus. Newer models have made this process more straightforward, often involving a C-arm that gives a clear image of the stone’s length and width. The C-arm is rotated to determine the stone’s height.
Ultrasound can also be used to locate and target stones during ESWL procedures. Ultrasounds don’t emit the ionizing radiation that fluoroscopy does and can visualize even stones that can’t be seen under x-rays. However, they might have a hard time identifying smaller stones, especially those located in the middle of the ureter or near a ureteral stent or catheter. Also, the success of ultrasounds in this process highly depends on the skills of the operator.
There are several factors that can predict the success of the ESWL treatment. These factors include the chemical composition, size, and number of stones, as well as the patient’s body mass index (BMI indicates obesity), kidney structure, skin-to-stone distance, and the extent of ureteral stone impaction. When many of these factors are unfavorable, other treatment options might be considered, such as ureteroscopy.
The chemical composition of the stones plays a significant role in determining the success rate of ESWL. Certain types of stones, like brushite, cystine, and pure calcium oxalate monohydrate stones are more resistant to fragmentation by shockwaves. Other treatments like ureteroscopy and laser lithotripsy might be more effective for these stones. Uric acid stones, on the other hand, can easily be fragmented by ESWL, but they can be challenging to spot without injecting a type of dye that helps visualize them during the procedure.
Also, patients with a high BMI (over 30), which indicates obesity, might have poorer outcomes from ESWL because the excess fatty tissue can weaken the shockwaves.
In terms of kidney structure, kidneys with short, wide tubes (the parts of the kidneys that connect to the small, cup-shaped parts, or calyces, where urine collects) and minimal distance from the stones to the lower part of the calyx are associated with better outcomes from ESWL. Furthermore, stones located in the upper or middle part of the calyx, a single stone less than 10mm, and a large angle between the upper and lower parts of the kidney can also enhance the success of the ESWL treatment.
Possible Complications of Extracorporeal Shockwave Lithotripsy
ESWL (Extracorporeal Shock Wave Lithotripsy) is a method used to break up kidney stones. It’s generally safe, but complications can occur in some instances. Here are the common ones:
* Abdominal aneurysm leakage or rupture: This is a rare but serious complication where the main blood vessel in the abdomen may leak or burst.
* Bacterial infections: After the surgery, there is a 10% chance of developing infections.
* Gastrointestinal (stomach and intestine) lesions: These are minor injuries and occur in 1.8% of cases.
* Blood in urine: This is usually temporary.
* Difficulty in finding or targeting the kidney stone: In such scenarios, additional imaging or a different procedure called ureteroscopy may be necessary.
* Incomplete breakup of kidney stones: This can lead to blockage of the urinary tract.
A particular blockage called Steinstrasse occurs in about 3% of all ESWL cases, with only 6% needing further surgery. This can be treated usually with medication but may require a small tube (double J stent), ureteroscopy, or a repeat ESWL. Occasionally, a bruise can form around the kidney in 1% to 4.6% of cases; patients who are on blood thinners or have high blood pressure are more at risk.
Kidney pain affects about 40% of patients and is usually managed with painkillers and medication to relax the muscles, with the potential need for a double-J stent or ureteroscopy. Occasionally, there can be minor injury to the kidney, which is treated conservatively. Skin bruising can also occur.
If the kidney stone doesn’t break up after 2 treatments, another ESWL treatment or an alternate therapy like ureteroscopy might be considered.
What Else Should I Know About Extracorporeal Shockwave Lithotripsy?
Nephrolithiasis, or kidney stones, can be treated in several ways. The first method is ESWL (extracorporeal shock wave lithotripsy). It doesn’t require any incisions and can get rid of about 75% of kidney stones, especially those smaller than 2 cm.
But for larger stones (over 2 cm), more invasive methods such as ureteroscopy (a procedure to see and remove stones in the urinary tract) or percutaneous nephrolithotomy (a surgery to remove large kidney stones) may be recommended. Even so, some people may choose ESWL since it does not involve a big surgery, despite the potential need for additional sessions.
Although ureteroscopy or percutaneous nephrolithotomy may remove kidney stones more effectively in one go, ESWL can yield similar success rates when combined with additional treatments if needed. ESWL also tends to be safer and less invasive.
Current research indicates that both ESWL and ureteroscopy can be equally effective in removing kidney stones. While ESWL may require multiple sessions, it can be less costly overall.
One major benefit of ESWL is its low complication rate (around 0%) when compared to ureteroscopy (3.2%). Also, ESWL can be easily used on any kidney stones, is well-tolerated, and causes minimal serious complications.
In preventing kidney stones, the primary measure is to take in more fluids, and follow certain preventive measures guided by 24-hour urine testing. However, this method’s success heavily relies on the patient’s willingness to comply.
This type of testing is especially recommended for those with specific conditions, including having surgically altered urinary system, gastrointestinal bypass surgery, high risk of anesthesia or surgery, irritable bowel syndrome, and serious conditions like morbid obesity, multiple previous urinary stone surgeries, nephrocalcinosis, and renal failure among others.