This document provides an overview of extracorporeal shockwave lithotripsy (ESWL) for treating kidney stones. ESWL uses shockwaves to break up stones into smaller fragments that can pass through the urinary tract. The document discusses the working principles, shockwave physics, types of lithotriptors, pre/intra/post-operative procedures, EAU guidelines, and factors that influence success rates, such as stone size and location. The take-home message is that ESWL has a stone-free rate of approximately 75% but the rate depends on stone characteristics and location, being lower for larger and lower pole stones.

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2. Extracorporeal
Shockwave Lithotripsy
(ESWL)
Presented by:
Dr. Afia Tehreem Gilanee
Resident Urology
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3. OBJECTIVES
Introduction To ESWL
Working Principle of a Lithotripter
Shockwave Physics
Types of Shockwave Sources
Pre-operative, Intraoperative And Post-operative Aspects
of SWL
EAU Guidelines On SWL
Take-home Message
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4. INTRODUCTION TO ESWL
A non invasive medical procedure used to treat
certain types of kidney stones
To break down kidney stones into smaller
fragments, allowing them to pass more easily
through urinary tract and be eliminated from body
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5. WORKING PRINCIPLE OF A LITHOTRIPTOR
1. Energy source- creates shock waves
2. Coupling Mechanism- transfers the energy
from outside to inside the body
3. Modes (fluoroscopic, ultrasonic or both)-
identifies and positions the calculus at focus
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6. LITHOTRIPTORS
Differ on the basis of
 Focal peak pressures (400-1500 bar)
 Focal dimensions (6*28mm to 50*15mm)
 Varied distances (12-17cm) between shockwave source and the target
 Generated pain
 Anaesthetic requirement
 Size
 Mobility
 Cost
 Durability
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7. LITHOTRIPTORS (Contd.)
The success rate of SWL- depends on the efficacy of
lithotripter and on
o size, location, and composition (hardness) of stones
o patient’s habitus
o performance of SWL
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8. SHOCKWAVE PHYSICS
Acoustic shockwaves – non harmonic
Non linear pressure characteristics
Steep rise in pressure amplitude –
compressive forces
2 basic types of shockwave sources
• Supersonic emitters
• Finite amplitude emitters
✓Piezoceramic
✓Electromagnetic
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9. SUPERSONIC EMITTERS
Release energy in a confined space – producing an
expanding plasma and an acoustic shockwave
Initial compression wave travels faster than speed of
sound in water
Rapidly slows down
Analogous to thunderstorm in nature
Can successfully fragment the calculi
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10. FINITE-AMPLITUDE EMITTERS
Create pulsed acoustic shockwaves
By displacing a surface activated by electrical
discharge
Piezoceramic-shockwaves after an electrical discharge
causes ceramic component to elongate- surface
displaced and acoustic pulse generated
Thousands of such components placed on concave
side of spherical surface directed towards a focus
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12. FINITE-AMPLITUDE EMITTERS (Contd.)
Electromagnetic systems-
electric discharge to a slab,
adjacent to an insulating
foil, creates an electric
current that repulses a metal
membrane – displacing it
and generating an acoustic
pulse in an adjacent medium
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15. FRAGMENTATION
Achieved by erosion and shattering
Erosion at entry and exit sites of shockwaves
Shattering –from energy absorption
Surrounding biologic tissues- resilient because neither brittle
nor focused
Acoustic energy focusing (AEF) devices- attach to the stones
External energy source- AEF device expands and cavitates-
fragmentation
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16. PREOPERATIVE EVALUATION
Vital signs monitoring
Physical examination
Investigations (X-ray KUB, USG)
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17. INTRAOPERATIVE ASPECTS
A.Stone Localization
➢ Proper patient positioning- pre requisite
➢Anteriorly located kidneys, medially oriented
portions of horseshoe kidney, or transplant
kidneys- best treated in prone position
➢Retrograde stents- easy identification
➢IV contrast agents- helpful in localization
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18. INTRAOPERATIVE ASPECTS (Contd.)
B. Imaging
1. Flouroscopic Imaging
• Dimmed room lighting and decreased radiation exposure
• Intermittent fluoroscopy- reveals movement with respiration
2. Ultrasonic Imaging
• Eliminates radiation exposure
• Can identify radiolucent or small caculi
• Ureteral or medially located ones- difficult esp if non obstructive
• Localization is difficult in obese
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19. INTRAOPERATIVE ASPECTS (Contd.)
C. Coupling
• Coupling devices- properties similar to those of
human skin
• Prevent pain, ecchymoses, hematomas, or skin
breakdown
• Water cushion coupling systems
• Coupling gel like those in USG
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20. INTRAOPERATIVE ASPECTS (Contd.)
D. Shockwave Triggering and Fragmentation
• Initially shockwaves were triggered with ECG
• Decrease the shockwaves during repolarization when
myocardium is most sensitive
• Shockwaves- trauma, including intrarenal and perirenal
hemorrhage and edema
• Minimal shocks should be delivered
• Determination of adequate fragmentation- Sharp edges
become fuzzy or blurred
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21. EAU GUIDELINES FOR SWL
 Routine use of internal stents before SWL does not improve stone-free
rates; however may reduce formation of steinstrasse
 Patients with a pacemaker can be treated with SWL
 Patients with implanted cardioverter defibrillators- special care;
 Starting SWL on a lower energy setting with stepwise power ramping
prevents renal injury
 Optimal shockwave frequency- 1-1.5Hz
 Repeat sessions feasible within 1 day for ureteral stones
 No standard antibiotic prophylaxis prior to SWL recommended
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22. POST-OPERATIVE CARE
Fluid intake should be encouraged
Asymptomatic individuals- Follow up- serial X ray KUB and
USG
Steinstrasse or stone gravel accumulation in ureter – severe
pain or fever
PCN drainage and decompressing the collecting systems
If uneffective- retrograde endoscopic manipulations
Severe pain unresponsive to routine IV or oral medications-
rare perirenal hematomas- CT scan for staging
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23. CONTRAINDICATIONS OF SWL
Pregnancy
Bleeding disorders (should be compensated 24hrs before and
48hrs after treatment)
Untreated UTIs
Severe skeletal malformations and severe obesity, (prevent
targeting of stone)
Arterial aneurysm in the vicinity of stone
Anatomical obstruction distal to the stone
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24. TAKE-HOME MESSAGE
Approximately 75% of patients treated with SWL- stone free in 3
months
Large pelvic stones (>1.5cm)- stone free rates at 3 months- 75%
Vs lower calyx- 35%
Small pelvic stones (<1.5cm)- stone free rate- 90%
Vs middle calyx(75%) or lower calyx (50%)
Increasing the size of stones- stone free rates decrease (more so in
lower and middle calyces than superior calyceal and pelvic locations)
Lower calyceal stone free rates- increased with small stone burden, a
short and wide infundibulum, and a non-acute infundibulo-pelvic angle
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Thank You!