Extracorporeal Shock Wave Lithotripsy: Comprehensive Guide for Surgeons

Extracorporeal Shock Wave Lithotripsy (ESWL) is a non-invasive medical procedure that uses shock waves to break down kidney stones, gallstones, and ureteral stones into smaller fragments, allowing them to be passed out of the body more easily. Since its introduction in the 1980s, ESWL has revolutionized the treatment of urolithiasis by providing an effective and less invasive alternative to open surgery and other treatment methods.

Indications

ESWL is primarily indicated for patients with kidney and ureteral stones that are less than 2 cm in diameter. The success of the procedure depends significantly on the careful selection of patients, which is based on factors such as the size, composition, and location of the stone, as well as the anatomy of the patient’s urinary tract.

1. Kidney Stones: ESWL is most effective for stones located in the kidney, especially those that are less than 2 cm in size. Stones that are larger or located in certain areas of the kidney may require additional procedures or alternative treatments.
2. Ureteral Stones: Stones located in the upper ureter are also good candidates for ESWL. However, stones in the lower ureter may be less responsive to shock wave treatment due to their proximity to the pelvis and other anatomical structures.
3. Non-Obstructive Stones: ESWL is suitable for non-obstructive stones, where the stone is not blocking the flow of urine. In cases where stones cause significant obstruction, other treatments might be preferred.
4. Patients Unable to Undergo Surgery: ESWL is an ideal option for patients who are not suitable candidates for invasive surgery due to comorbidities or high surgical risk.

Preoperative Evaluation

A thorough preoperative evaluation is essential to determine the suitability of a patient for ESWL and to maximize the success rate of the procedure. This evaluation typically includes:

1. Imaging Studies:
   • X-Ray and Ultrasound: These are used to locate and measure the stone, as well as to assess the anatomy of the kidneys and urinary tract.
   • CT Scan: Provides detailed information about the size, density, and exact location of the stone, and is useful in planning the treatment approach.
2. Blood and Urine Tests: These are performed to evaluate kidney function, identify any infection, and determine if there are any bleeding disorders that could complicate the procedure.
3. Patient Medical History: A detailed medical history helps to identify any contraindications to ESWL, such as a history of bleeding disorders, pregnancy, or severe skeletal abnormalities that could affect the positioning during the procedure.

Contraindications

Not all patients are suitable candidates for ESWL. Some contraindications include:

1. Pregnancy: ESWL is contraindicated during pregnancy due to the potential risk to the fetus from the shock waves.
2. Coagulopathy: Patients with bleeding disorders or those on anticoagulant therapy may be at increased risk of hemorrhage during or after ESWL.
3. Obesity: Severe obesity can make it difficult to position the patient correctly for the procedure and may reduce the effectiveness of the shock waves.
4. Skeletal Abnormalities: Conditions such as severe scoliosis or other spinal deformities can make it challenging to properly align the patient with the lithotripter.
5. Infection: Active urinary tract infections should be treated before ESWL to reduce the risk of sepsis following the procedure.
6. Anatomical Abnormalities: Certain anatomical variations, such as horseshoe kidneys, may make ESWL less effective.

Surgical Techniques and Steps

ESWL is typically performed on an outpatient basis under sedation or light anesthesia. The procedure involves several steps:

1. Positioning the Patient: The patient is positioned on the lithotripter table, usually lying on their back. Proper positioning is crucial to align the stone with the focal point of the shock waves.
2. Imaging Guidance: Continuous imaging (usually fluoroscopy or ultrasound) is used to locate the stone and guide the shock waves.
3. Administration of Shock Waves: A series of high-energy shock waves is directed at the stone. These shock waves pass through the skin and tissues, breaking the stone into smaller fragments. The number of shocks and the energy level are carefully controlled to optimize stone fragmentation while minimizing damage to surrounding tissues.
4. Monitoring: The patient’s vital signs and the position of the stone are continuously monitored throughout the procedure. Adjustments to the shock wave delivery may be made as needed.
5. Post-Procedure Evaluation: After the procedure, imaging may be repeated to assess the degree of stone fragmentation.

Postoperative Care

After ESWL, patients are typically monitored for a few hours before being discharged. Postoperative care includes:

1. Pain Management: Patients may experience mild to moderate pain as the stone fragments pass through the urinary tract. Pain is usually managed with oral analgesics.
2. Hydration: Patients are encouraged to drink plenty of fluids to help flush out the stone fragments.
3. Activity Restrictions: Patients are generally advised to avoid strenuous activities for a few days to prevent complications such as bleeding.
4. Follow-Up Imaging: A follow-up imaging study is usually performed within a few weeks to confirm that the stone fragments have passed and to check for any residual stones.
5. Infection Monitoring: Any signs of infection, such as fever or persistent pain, should be promptly evaluated.

Possible Complications

While ESWL is generally safe, there are potential complications that surgeons should be aware of:

1. Hematuria: Blood in the urine is common after ESWL and usually resolves within a few days.
2. Pain: Some patients may experience significant pain as the stone fragments pass through the urinary tract.
3. Infection: There is a risk of urinary tract infection following ESWL, particularly if there is incomplete stone fragmentation.
4. Steinstrasse: This refers to a complication where stone fragments form a "stone street" in the ureter, potentially causing obstruction. This may require additional treatment.
5. Subcapsular Hematoma: Although rare, the formation of a hematoma in the kidney or surrounding tissues can occur, which may require intervention.

Different Techniques

There are variations in ESWL techniques based on the type of lithotripter used and the approach to patient positioning:

1. Electrohydraulic Lithotripsy: Utilizes an electrical discharge to create shock waves. It was the first type of ESWL but is less commonly used today due to the development of newer technologies.
2. Electromagnetic Lithotripsy: Generates shock waves using an electromagnetic coil. It is widely used due to its precision and lower risk of tissue damage.
3. Piezoelectric Lithotripsy: Uses piezoelectric crystals to generate shock waves. It is considered very precise but may require more shock waves to fragment the stone compared to other methods.
4. Focused vs. Unfocused Shock Waves: Focused shock waves are targeted directly at the stone, while unfocused waves spread out over a larger area. The choice depends on the stone's characteristics and the patient's anatomy.

Prognosis and Outcome

The success rate of ESWL varies based on several factors:

1. Stone Size and Composition: Smaller stones and those made of softer materials like uric acid or calcium oxalate are more likely to be successfully fragmented by ESWL.
2. Stone Location: Stones located in the kidney or upper ureter tend to have better outcomes compared to those in the lower ureter.
3. Patient Factors: Patient anatomy, stone composition, and overall health can affect the success of the procedure.

Overall, ESWL has a success rate of 70-90% for appropriately selected stones, with most patients achieving stone-free status after one or two treatment sessions.

Alternative Options

For stones that are not suitable for ESWL, alternative treatments include:

1. Ureteroscopy: A minimally invasive procedure where a small scope is inserted into the ureter to remove or fragment the stone with a laser.
2. Percutaneous Nephrolithotomy (PCNL): A more invasive procedure where a small incision is made in the back to access the kidney and remove the stone directly. This is often used for larger or more complex stones.
3. Medical Expulsive Therapy: Involves the use of medications to help pass the stone naturally, typically used for small stones.
4. Open Surgery: Rarely performed today due to the effectiveness of less invasive methods, but may be necessary for very large or complex stones.

Average Cost

The cost of ESWL can vary depending on the country, healthcare system, and specific circumstances of the patient. In the United States, the cost ranges from $5,000 to $10,000, including the procedure, anesthesia, and follow-up care. In countries with universal healthcare, the cost may be lower or covered entirely by the healthcare system.

Recent Advances

Recent advances in ESWL include:

1. Improved Imaging Techniques: The use of advanced imaging methods such as 3D ultrasound and real-time CT scanning has improved the precision and effectiveness of ESWL.
2. Second-Generation Lithotripters: Newer lithotripters are more powerful, have better stone fragmentation rates, and are associated with fewer side effects.
3. Combination Therapies: Combining ESWL with medical therapies or other minimally invasive procedures has improved outcomes for patients with complex stones.
4. Targeted Shock Waves: Research is ongoing to develop shock waves that are more targeted and cause less damage to surrounding tissues.