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Urolithiasis management- eswl

This document provides information about extracorporeal shockwave lithotripsy (ESWL). It discusses the physics behind shockwaves, different lithotripter generators (electrohydraulic, electromagnetic, piezoelectric), focusing systems, imaging for stone localization, and mechanisms of stone fragmentation. It also covers indications and contraindications for ESWL, factors influencing success rates like stone size and composition, and preoperative considerations like antibiotic prophylaxis and stenting. The goal of ESWL is to pulverize kidney stones into small enough fragments that can pass spontaneously without invasive procedures.

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EXTRACORPOREAL SHOCKWAVE LITHOTRIPSY Dept of Urology Govt Royapettah Hospital and Kilpauk Medical College Chennai 1
Moderators: Professors: • Prof. Dr. G. Sivasankar, M.S., M.Ch., • Prof. Dr. A. Senthilvel, M.S., M.Ch., Asst Professors: • Dr. J. Sivabalan, M.S., M.Ch., • Dr. R. Bhargavi, M.S., M.Ch., • Dr. S. Raju, M.S., M.Ch., • Dr. K. Muthurathinam, M.S., M.Ch., • Dr. D. Tamilselvan, M.S., M.Ch., • Dr. K. Senthilkumar, M.S., M.Ch. Dept of Urology, GRH and KMC, Chennai. 2
PHYSICS • An acoustic wave, or sound wave, is created whenever an object moves within a fluid (a fluid can be either a gas or liquid) • Abrupt release of energy in a small space- high energy amplitudes – shock waves • Shockwaves thro substances of differing impedance – compressive stresses at boundary surface • IMPLOSION rather than explosion 3 Dept of Urology, GRH and KMC, Chennai.
Shock wave • It represents a short- duration (<10μs) acoustic pressure wave consisting of a compressive phase (peak pressure: 30– 100MPa) followed by a tensile phase (negative pressure)-10mpa • 150–800 kHz 4 Dept of Urology, GRH and KMC, Chennai.
• Goal of SWL is to pulverize kidney stones into gravels for spontaneous discharge in urine without inflicting adverse effects to surrounding tissues 5 Dept of Urology, GRH and KMC, Chennai.
LITHOTRIPTOR • shock‐wave generator • focusing device • coupling medium • stone localization system. 6 Dept of Urology, GRH and KMC, Chennai.
SHOCK WAVE GENERATOR • Electrohydraulic (spark gap) • Electromagnetic • Piezoelectric 7 Dept of Urology, GRH and KMC, Chennai.
• ELECTROHYDRAULIC (SPARK GAP) GENERATOR • shockwave is generated by an underwater spark discharge • generate a strong converging acoustic wave • shockwave focused onto a calculus - ellipsoid reflector 8 Dept of Urology, GRH and KMC, Chennai.
9 Dept of Urology, GRH and KMC, Chennai.
• Advantage • Very effective in breaking kidney stones • Disadvantages • Pressure fluctuations from shock to shock • Short electrode life 10 Dept of Urology, GRH and KMC, Chennai.
ELECTROMAGNETIC GENERATOR • Two conducting cylindrical plates separated by a thin insulating sheet • plane or cylindrical shockwave • Cylindrical waves - Focused by acoustic lens/parabolic reflector 11 Dept of Urology, GRH and KMC, Chennai.
Electromagnetic shockwave generator 12 Dept of Urology, GRH and KMC, Chennai.
• ADVANTAGES • more controllable and reproducible than electrohydraulic generators • Less pain (introduction of energy over a large skin area) • Small focal point with high-energy densities (very effective in breaking stones) • No need for frequent electrode replacement • DISSADVANTAGE • Increased rate of subcapsular hematoma • (small focal point of high energy) 13 Dept of Urology, GRH and KMC, Chennai.
PIEZOELECTRIC GENERATOR • small, polarized, polycrystalline, ceramic elements (barium titanate) - induced by application of high‐voltage (1–10 kV) – generate a strong converging acoustic wave • Focused by center of the spherical dish 14 Dept of Urology, GRH and KMC, Chennai.
Piezoelectric shockwave generator - polarized polycrystalline ceramic elements in spherical dish 15 Dept of Urology, GRH and KMC, Chennai.
• Advantages • High focusing accuracy • Long service life • No need for anesthesia- low energy density at the skin entry point • Disadvantage • low energy density, reduces effectiveness of breaking stones 16 Dept of Urology, GRH and KMC, Chennai.
FOCUSSING SYSTEMS • Electrohydraulic – Ellipsoid • Piezo-electric – Hemispherical dish • Electromagnetic – acoustic lens (Siemens) • Parabolic (Storz) 17 Dept of Urology, GRH and KMC, Chennai.
18 Dept of Urology, GRH and KMC, Chennai.
OTHER GENERATORS • Microexplosive generators • explosion of tiny lead azide pellets within a parabolic reflector generates –shockwave • storage , handling of the volatile lead azide pellets- difficult • Laser beam • Multistage light gas gun • Not successful commercialy 19 Dept of Urology, GRH and KMC, Chennai.
CHARACTERISTICS OF A LITHOTRIPTOR SHOCK WAVE  wave is a short pulse of about 5--10 μs duration  consists of positive pressure shock (compressive wave) with pressures of about 40 MPa ,lasting about 1-2 μs  followed by a longer, lower amplitude (tensile wave) negative pressure of 10 MPa,lasts about 3-5 μs • focal point is Ellipsoidal/cigar in shape, with its longest dimension along the central axis of lithotripter • Length and diameter of the focal zone depends on – diameter of the source – focal length 20 Dept of Urology, GRH and KMC, Chennai.
• Intensity transmission of acoustic wave water to tissue is very high • water-to-stone transmission is high (75 to 95% energy transmitted into the stones) • water-air - 99.9% reflected (shock wave generators in lithotripsy are water-filled) 21 Dept of Urology, GRH and KMC, Chennai.
The ideal lithotripter • moderate positive peak pressure, p+ • sufficient disintegration power (effective energy, E12mm) to disintegrate hard stones and to compensate or shock‐wave attenuation (obesity) • minimal cavitation effects and hence minimal risk of adverse tissue effects. 22 Dept of Urology, GRH and KMC, Chennai.
SHOCK WAVE COUPLING MEDIUM Dornier HM3 lithotripter • Large water bath • required general or spinal anesthesia • Second generation lithotriptor • water cushion or partial water bath • Third‐generation lithotripters • Allow anesthesia‐free treatments. • both fluoroscopy and ultrasound,use possible • both SWL and endourologic procedures are possible(multifunctional system) • Facilitates prone position • (middle ureter, horseshoe kidneys, or pelvic kidneys) 23 Dept of Urology, GRH and KMC, Chennai.
IMAGING FOR STONE LOCALIZATION • Ultrasonography • Isocentric Fluoroscopy • Combination of ultrasonography and fluoroscopy 24 Dept of Urology, GRH and KMC, Chennai.
Choice of the ideal lithotripter for any given stone center • A multifunctional workstation for SWL and endourologic procedures is the best choice for centers with an adequate patient load in both treatment modalities. • An integrated or hybrid design makes economic sense in very active stone centers. • In centers with a modest patient load a modular system may probably be the better choice 25 Dept of Urology, GRH and KMC, Chennai.
ESWL-HISTORY • Dornier HM I -1980 • HM II- 1982 • Dornier HM III – 1984 • Portable Dornier – 1996 • Dornier HM IV - 1997 26 Dept of Urology, GRH and KMC, Chennai.
MECHANISM 27 Dept of Urology, GRH and KMC, Chennai.
Traditional theories of stone fragmentation • stress gradient and tensile failure at stone/ fluid boundaries • Acoustic cavitations • Squeezing Compression fracture • quasi‐static squeezing(wide focus with lower pressure to enhance) • Hopkins effect (cavitation and shear forces) • Spallation • Dynamic fatigue • dynamic squeezing 28 Dept of Urology, GRH and KMC, Chennai.
29 Dept of Urology, GRH and KMC, Chennai.
30 Dept of Urology, GRH and KMC, Chennai.
Spallation • Reflected tensile wave at distal surface of the stone with maximum tension at the distal part of the stone • Spalling will gradually become less effective as the size of fragments decreases or in stones with curved boundaries or when wave attenuation in the stone material is high • Breaking the stone from the inside 31 Dept of Urology, GRH and KMC, Chennai.
Tear and shear • Pressure gradients resulting from impedance changes at the stone front and distal surface with pressure inversion • Stone made of layers • Hammer-like action resulting in a crater-like fragmentation 32 Dept of Urology, GRH and KMC, Chennai.
Quasi-static squeezing • Pressure gradient between circumferential and longitudinal waves results in squeezing of the stone • Nutcracker-like action 33 Dept of Urology, GRH and KMC, Chennai.
cavitation • Cavitation is defined as the formation and collapse of bubbles • Negative pressure waves induce a collapsing cavitation bubble at the stone surface • Microexplosive erosion at the proximal and distal ends of the stone 34 Dept of Urology, GRH and KMC, Chennai.
Dynamic squeezing • Shear waves initiated at the corners of the stone and driven by squeezing waves along the calculus lead to the greatest stress and tension • Nutcracker-like action in combination with spalling 35 Dept of Urology, GRH and KMC, Chennai.
• squeezing will be enhanced when the entire stone falls within the diameter of the focal zone • If lithotripters have very small focal zones this mechanism will be ineffective 36 Dept of Urology, GRH and KMC, Chennai.
SUPERFOCUSING Shockwave passed in to stone get reflected at the distal surface of the stone focused either by refraction or by diffraction from the corners of the stone to interior of stone fragmentation 37 Dept of Urology, GRH and KMC, Chennai.
38 Dept of Urology, GRH and KMC, Chennai.
39 Dept of Urology, GRH and KMC, Chennai.
Unified mechanism 40 Dept of Urology, GRH and KMC, Chennai.
A heuristic model of stone comminution in SWL 1. P+(avg) (controlled by the output kV or energy setting of the lithotripter) and 2 .dose of the shock waves delivered • Effective treatment can be achieved by using moderate P+(avg) in the range of 15–20 MPa within 2000 shocks. • progressive ramping of the lithotripter output (and thus P+(avg)) that can achieve effective stone comminution with minimal risk of tissue injury 41 Dept of Urology, GRH and KMC, Chennai.
42 Dept of Urology, GRH and KMC, Chennai.
AIM • Fragment the stone to 1mm pieces- IDEAL • <= 4 mm acceptable • Clearance may take 3-4 weeks,varies among patients 43 Dept of Urology, GRH and KMC, Chennai.
CONTRAINDICATION • Urinary Tract Infection • Pregnancy • Uncorrected Coagulopathy • Arterial aneurysms in close proximity to target stone • Uncontrolled hypertension • Distal obstruction • Morbid Obesity • Spinal Deformity or Limb Contractures 44 Dept of Urology, GRH and KMC, Chennai.
SWL TREATMENT OF RENAL AND URETERAL CALCULI RENAL CALCULI • To achieve maximal stone clearance with minimal morbidity 45 Dept of Urology, GRH and KMC, Chennai.
INDICATION • Pain • Infection • Obstruction 46 Dept of Urology, GRH and KMC, Chennai.
Stone size and location • SWL stone‐free rates at 3 months are 86–89% for renal pelvis, 71–83% for upper calyx, 73–84% for middle calyx, and 37–68% lower calyx stones • 10 mm or less - 74% ( 60 to 90%) • 11 to 20 mm - 54% ( 50 to 83%) • >20 mm - 33% ( 33 to 81%) 47 Dept of Urology, GRH and KMC, Chennai.
48 Dept of Urology, GRH and KMC, Chennai.
SMALL, ASYMPTOMATIC CALYCEAL STONES (<5mm) Controversial Most calyceal stones, in the absence of intervention, are likely to increase in size, causing symptoms of pain or infection prophylactic SWL - targeting may be difficult Indication pediatric patients solitary kidney High-risk professions ( pilots) Women considering pregnancy 49 Dept of Urology, GRH and KMC, Chennai.
TREATMENT DECISIONS BY STONE COMPOSITION • Fragmentation by SWL is variable among stones of different composition • Cystine • Brushite calculi • Calcium oxalate monohydrate • matrix • most resistant to SWL, produce large pieces that may be difficult to clear from the collecting system 50 Dept of Urology, GRH and KMC, Chennai.
• Brushite, cystine, calcium oxalate monohydrate should be treated by SWL only when the stone burden is small (<1.5 cm) • Larger stones -- PNL or ureteroscopy • Matrix calculi • Radiolucent ,associated with urea-splitting bacteriuria • SWL is not effective (gelatinous nature ) • PNL , ureteroscopy – choice 51 Dept of Urology, GRH and KMC, Chennai.
PREDICTION OF STONE COMPOSITION (STONE FRAGILITY) • PLAIN X-RAY KUB - smooth-edged stones, homogeneous, more dense than bone -- require more shockwaves • Round, radially reticulated stones with spiculated edges or stones with irregular margin – good fragmentation • Accuracy - 39% 52 Dept of Urology, GRH and KMC, Chennai.
• NON–CONTRAST-ENHANCED HELICAL CT • basis of attenuation values • success rate - lower for calculi with attenuation values greater than 1000 Hounsfield units • Distinguish stone types • Uric acid from calcium stones 53 Dept of Urology, GRH and KMC, Chennai.
Hounsfield density • CT attenuation values are greater than 900–1000 HU • Skin‐SSD was measured by averaging the distance between the center of the stone 54 Dept of Urology, GRH and KMC, Chennai.
Predictive models of shock‐wave lithotripsy success 55 Dept of Urology, GRH and KMC, Chennai.
Preoperative considerations • Antibiotic prophylaxis • in the absence of urinary tract infections or other risk factors ,antibiotic prophylaxis prior to SWL is not indicated 56 Dept of Urology, GRH and KMC, Chennai.
DJ STENTING • stone‐free rate in those who were stented preoperatively was 78.1 versus 83% in the stentless group (P = 0.27). • The presence of a stent also does not prevent renal colic, steinstrasse, or additional procedures • Current guidelines no longer recommend routine preoperative stenting 57 Dept of Urology, GRH and KMC, Chennai.
INDICATIONS FOR STENTING • Large stone burden >1.5 cm • Obstructed system • Pyonephrosis • Poorly visualised stones 58 Dept of Urology, GRH and KMC, Chennai.
INTRA-OPERATIVE DETAILS • no conclusive data to recommend an optimum number of shock waves(2000–3000 shock waves) • 60-90 shocks / min • Negative pressure phase of a shock wave becomes dampened at a faster rate(responsible for cavitation bubbles) • benefits of a slower shockwave rate are most notable for stones >10 mm 59 Dept of Urology, GRH and KMC, Chennai.
Pretreatment • application of low‐energy shock waves to the targeted renal stone in order to “prime the kidney” and reduce renal injury( associated with renal vasoconstriction) • 300 -500 shock waves applied at 12 kV proven to significantly reduce the hemorrhagic lesion size(20 times!) • 3-4 min pause also decreases hemorrahge 60 Dept of Urology, GRH and KMC, Chennai.
SHOCK WAVE ADMINISTRATION • Voltage – 12 - 24kV • Power – 100- 120 Hz • Number of shock waves – 60-90/min • Sequence of shock wave delivery – Step wise power ramping – shock wave intensityis gradually increased – Two -Step power ramping – (Low to High) – 100 waves at 18kV followed by 2000 waves at 24kV 61 Dept of Urology, GRH and KMC, Chennai.
Renal Stone • non staghorn – ideal 6-10mm • 10-20mm in the absence of other factors • >20mm not recommended 62 Dept of Urology, GRH and KMC, Chennai.
RENAL ANATOMIC FACTORS • Ureteropelvic junction obstruction • Horseshoe kidney • Ectopic or fusion anomalies • Calyceal diverticula 63 Dept of Urology, GRH and KMC, Chennai.
Lower pole stones • Less than 10mm ESWL • 10-20mm –infundibulopelvic angle more than 70deg, infundibular width more than 4mm,infundibulum length less than 3cm are favourable. • More than 20mm PCNL 64 Dept of Urology, GRH and KMC, Chennai.
PUJ obstruction,megaureter, duplicated ureter with hydronephrosis Renal scintigraphy should be considered to rule out clinically significant obstruction. Three month stone‐free rates for these anatomical variations in those without obstruction range from 40–55% CALICEAL DIVERTICULAM SWL - Stone-free rates are low (0-25%) May be useful for stones <1 cm in size only if there confirmed, short and patent diverticular neck which could allow fragment passage URINARY DIVERSION colon conduits is 3–4% and with ileal conduits is 10–20% SWL monotherapy was found to have an 81.5% success 65 Dept of Urology, GRH and KMC, Chennai.
66 Dept of Urology, GRH and KMC, Chennai.
CARDIAC PATIENTS • Gated Lithotripsy(at R wave) • Pace makers – guarded procedure • rotating the patient 15–20° 67 Dept of Urology, GRH and KMC, Chennai.
CHILDREN • SWL for stones >2 cm in size, including staghorn calculi, can be effective and is acceptable in children • Lung protection – Styrofoam paddings • Low kV and No. of shocks • Exit site shielding with wet towels –decreased echymosis 68 Dept of Urology, GRH and KMC, Chennai.
Adjunct therapy after shock‐wave lithotripsy • to improve stone clearance after SWL, especially for lower pole stones • Involve drinking500 ml of water 30 minutes prior to inversion in a proneTrendelenburg position at 45° and continuous manual mechanical percussion over the flank for 10 minute 69 Dept of Urology, GRH and KMC, Chennai.
Medical therapy after shock‐wave lithotripsy • α‐adrenergic antagonists • phyllanthus niruri, a Brazilian plant remedy which prevents calcium oxalate crystal • potassium citrate 70 Dept of Urology, GRH and KMC, Chennai.
Follow‐up after SWL • No consensus on follow‐up imaging after SWL. • Obtaining plain Xray KUB 1–4 weeks after SWL • Document SWL failure as being after three sessions • Offer endoscopic therapy as the next treatment option in those who fail a single session 71 Dept of Urology, GRH and KMC, Chennai.
ESWL FAILURE • PCNL • RIRS • SANDWICH • OPEN STONE SURGERY 72 Dept of Urology, GRH and KMC, Chennai.
Ureteric stone • Proximal ureteric stones<1cm ESWL insitu • SSD cutoff of 11–12 cm • 70–97% for proximal stones, 58–97.8% for mid‐ureteral stones, and 54–97.9% for distal ureteral calculi • Impacted stones are resistant 73 Dept of Urology, GRH and KMC, Chennai.
ESWL & URETERIC CALCULI • For fragmentation fluid medium around stone necessary • If stones impacted fragmentation may not occur • “PUSH & BANG”-success Marginally HIGHER THAN “in situ ESWL” 74 Dept of Urology, GRH and KMC, Chennai.
• rotating the patient toward the therapy head increased the success rate significantly for mid‐ and distal ureteral calculi (from 83.9 to 95% and from 89.1 to 98.0% respectively) and a significant decrease in number of SWL sessions for proximal stones 75 Dept of Urology, GRH and KMC, Chennai.
Ureteric stone 76 Dept of Urology, GRH and KMC, Chennai.
• Factor for spontaneous passage of stone • Width of the stone • Location • Width of the stone • Stones < 4 mm -- rates of spontaneous passage of 80% • 4 to 6 mm -- 59% • > 6 mm – 21% • Location • Proximal -- 22% • Middle -- 46% • Distal ureter -- 71% • Stones of 5 mm or less, conservative management 77 Dept of Urology, GRH and KMC, Chennai.
Complication of eswl • Hematuria most common,resolves within a few hours. • effect in vessels can be differentiated by measuring α2‐ macroglobulin enhancement found immediately after and 1 day following SWL • Detoriation of renal function • Renal colic 78 Dept of Urology, GRH and KMC, Chennai.
Complications • Steinstrasse • (Coptcoat’s classification of steinstrasse exists (Type I, fragments <2 mm in diameter; Type II, leading fragment 4–5 mm tailed by 2 mm particles; and Type III,consisting of large fragments), • Infectious complications: 5.1% in spite of preoperative sterile urine. MC Escherichia coli 79 Dept of Urology, GRH and KMC, Chennai.
COMPLICATION Extrarenal Injury Renal Injury Acute Chronic 80 Dept of Urology, GRH and KMC, Chennai.
EXTRARENAL INJURY • Liver • skeletal muscle – pain at site of entry • Gastric and duodenal erosion • Lung parenchyma • Acute pancreatitis • Hematochezia - mucosal damage of the colon • Myocardial infarctions, cerebral vascular accidents • cardiac arrhythmia 11and 59% during ungated SWL • Sperm count 81 Dept of Urology, GRH and KMC, Chennai.
• ACUTE RENAL INJURY • Structural • Functional • Hemorrhage and edema within or around the kidney • Intrarenal edema ,Subcapsular hematoma (3% - 12%) • 6 weeks - 24 months to resolve 82 Dept of Urology, GRH and KMC, Chennai.
2,000 shocks at 12 (A), 18 (B), 24 (C) Kv subcapsular hematona increases with increasing kV level 83 Dept of Urology, GRH and KMC, Chennai.
Bilateral perinephric hematomas following bilateral simultaneous ESWL 84 Dept of Urology, GRH and KMC, Chennai.
• CHRONIC RENAL INJURY • Structural • Functional • chronic renal changes - due to scar formation • Accelerated rise in systemic blood pressure • Decrease in renal function • Increase in the rate of stone recurrence (residual stone debris) 85 Dept of Urology, GRH and KMC, Chennai.
• CHRONIC HISTOLOGIC CHANGES • Nephron loss • Dilated veins • Diffuse interstitial fibrosis • Calcium and hemosiderin deposits • Hyalinized and acellular scars from cortex to medulla 86 Dept of Urology, GRH and KMC, Chennai.
Steinstrasse ( or Stone Street) – Post ESWL 87 Dept of Urology, GRH and KMC, Chennai.
Factors influencing renal trauma • No of shocks 500-8000 • Period of shock wave, decreased period increased damage • Kidney size • Children • Preexisting RD • Scarring 2% in adults &7% in children • Lithotripter output settings such as output energy and energy flux density, total number of shocks, • pre‐existing hypertension in older 88 Dept of Urology, GRH and KMC, Chennai.
Damage control • Use of low power.12-15 kv • Priming of kidney • Treat at slow shock wave rate- 1 S W per sec. • Sedation. • Number of shock waves to be less • Maximum session 3-5.interval bt session 10- 14 days. 89 Dept of Urology, GRH and KMC, Chennai.
Dornier HM-3 90 Dept of Urology, GRH and KMC, Chennai.
Siemens Lithostar lithotriptor 91 Dept of Urology, GRH and KMC, Chennai.
LithoDiamond with portable C-arm (modular designs) 92 Dept of Urology, GRH and KMC, Chennai.
• TANDEM-PULSE LITHOTRIPTER • Lithotripter with auxiliary piezoelectric head to generate a second shock wave along the same acoustic axis • Two shock waves are used in rapid succession to drive forceful collapse of bubbles against stone • DUAL PULSE LITHOTRIPSY • Two lithotriptor generate pulses,released simultaneously, both focused at the same F2 - minimize cavitation • 93 Dept of Urology, GRH and KMC, Chennai.
Dual pulse lithotripsy. Coaxially aligned electrohydraulic shock wave sources with a common F2 94 Dept of Urology, GRH and KMC, Chennai.
95 Dept of Urology, GRH and KMC, Chennai.

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Urolithiasis management- eswl

  • 1.
    EXTRACORPOREAL SHOCKWAVE LITHOTRIPSY Dept ofUrology Govt Royapettah Hospital and Kilpauk Medical College Chennai 1
  • 2.
    Moderators: Professors: • Prof. Dr.G. Sivasankar, M.S., M.Ch., • Prof. Dr. A. Senthilvel, M.S., M.Ch., Asst Professors: • Dr. J. Sivabalan, M.S., M.Ch., • Dr. R. Bhargavi, M.S., M.Ch., • Dr. S. Raju, M.S., M.Ch., • Dr. K. Muthurathinam, M.S., M.Ch., • Dr. D. Tamilselvan, M.S., M.Ch., • Dr. K. Senthilkumar, M.S., M.Ch. Dept of Urology, GRH and KMC, Chennai. 2
  • 3.
    PHYSICS • An acousticwave, or sound wave, is created whenever an object moves within a fluid (a fluid can be either a gas or liquid) • Abrupt release of energy in a small space- high energy amplitudes – shock waves • Shockwaves thro substances of differing impedance – compressive stresses at boundary surface • IMPLOSION rather than explosion 3 Dept of Urology, GRH and KMC, Chennai.
  • 4.
    Shock wave • Itrepresents a short- duration (<10μs) acoustic pressure wave consisting of a compressive phase (peak pressure: 30– 100MPa) followed by a tensile phase (negative pressure)-10mpa • 150–800 kHz 4 Dept of Urology, GRH and KMC, Chennai.
  • 5.
    • Goal ofSWL is to pulverize kidney stones into gravels for spontaneous discharge in urine without inflicting adverse effects to surrounding tissues 5 Dept of Urology, GRH and KMC, Chennai.
  • 6.
    LITHOTRIPTOR • shock‐wave generator •focusing device • coupling medium • stone localization system. 6 Dept of Urology, GRH and KMC, Chennai.
  • 7.
    SHOCK WAVE GENERATOR •Electrohydraulic (spark gap) • Electromagnetic • Piezoelectric 7 Dept of Urology, GRH and KMC, Chennai.
  • 8.
    • ELECTROHYDRAULIC (SPARKGAP) GENERATOR • shockwave is generated by an underwater spark discharge • generate a strong converging acoustic wave • shockwave focused onto a calculus - ellipsoid reflector 8 Dept of Urology, GRH and KMC, Chennai.
  • 9.
    9 Dept of Urology,GRH and KMC, Chennai.
  • 10.
    • Advantage • Veryeffective in breaking kidney stones • Disadvantages • Pressure fluctuations from shock to shock • Short electrode life 10 Dept of Urology, GRH and KMC, Chennai.
  • 11.
    ELECTROMAGNETIC GENERATOR • Twoconducting cylindrical plates separated by a thin insulating sheet • plane or cylindrical shockwave • Cylindrical waves - Focused by acoustic lens/parabolic reflector 11 Dept of Urology, GRH and KMC, Chennai.
  • 12.
    Electromagnetic shockwave generator12 Dept of Urology, GRH and KMC, Chennai.
  • 13.
    • ADVANTAGES • morecontrollable and reproducible than electrohydraulic generators • Less pain (introduction of energy over a large skin area) • Small focal point with high-energy densities (very effective in breaking stones) • No need for frequent electrode replacement • DISSADVANTAGE • Increased rate of subcapsular hematoma • (small focal point of high energy) 13 Dept of Urology, GRH and KMC, Chennai.
  • 14.
    PIEZOELECTRIC GENERATOR • small,polarized, polycrystalline, ceramic elements (barium titanate) - induced by application of high‐voltage (1–10 kV) – generate a strong converging acoustic wave • Focused by center of the spherical dish 14 Dept of Urology, GRH and KMC, Chennai.
  • 15.
    Piezoelectric shockwave generator- polarized polycrystalline ceramic elements in spherical dish 15 Dept of Urology, GRH and KMC, Chennai.
  • 16.
    • Advantages • Highfocusing accuracy • Long service life • No need for anesthesia- low energy density at the skin entry point • Disadvantage • low energy density, reduces effectiveness of breaking stones 16 Dept of Urology, GRH and KMC, Chennai.
  • 17.
    FOCUSSING SYSTEMS • Electrohydraulic– Ellipsoid • Piezo-electric – Hemispherical dish • Electromagnetic – acoustic lens (Siemens) • Parabolic (Storz) 17 Dept of Urology, GRH and KMC, Chennai.
  • 18.
    18 Dept of Urology,GRH and KMC, Chennai.
  • 19.
    OTHER GENERATORS • Microexplosivegenerators • explosion of tiny lead azide pellets within a parabolic reflector generates –shockwave • storage , handling of the volatile lead azide pellets- difficult • Laser beam • Multistage light gas gun • Not successful commercialy 19 Dept of Urology, GRH and KMC, Chennai.
  • 20.
    CHARACTERISTICS OF ALITHOTRIPTOR SHOCK WAVE  wave is a short pulse of about 5--10 μs duration  consists of positive pressure shock (compressive wave) with pressures of about 40 MPa ,lasting about 1-2 μs  followed by a longer, lower amplitude (tensile wave) negative pressure of 10 MPa,lasts about 3-5 μs • focal point is Ellipsoidal/cigar in shape, with its longest dimension along the central axis of lithotripter • Length and diameter of the focal zone depends on – diameter of the source – focal length 20 Dept of Urology, GRH and KMC, Chennai.
  • 21.
    • Intensity transmissionof acoustic wave water to tissue is very high • water-to-stone transmission is high (75 to 95% energy transmitted into the stones) • water-air - 99.9% reflected (shock wave generators in lithotripsy are water-filled) 21 Dept of Urology, GRH and KMC, Chennai.
  • 22.
    The ideal lithotripter •moderate positive peak pressure, p+ • sufficient disintegration power (effective energy, E12mm) to disintegrate hard stones and to compensate or shock‐wave attenuation (obesity) • minimal cavitation effects and hence minimal risk of adverse tissue effects. 22 Dept of Urology, GRH and KMC, Chennai.
  • 23.
    SHOCK WAVE COUPLINGMEDIUM Dornier HM3 lithotripter • Large water bath • required general or spinal anesthesia • Second generation lithotriptor • water cushion or partial water bath • Third‐generation lithotripters • Allow anesthesia‐free treatments. • both fluoroscopy and ultrasound,use possible • both SWL and endourologic procedures are possible(multifunctional system) • Facilitates prone position • (middle ureter, horseshoe kidneys, or pelvic kidneys) 23 Dept of Urology, GRH and KMC, Chennai.
  • 24.
    IMAGING FOR STONELOCALIZATION • Ultrasonography • Isocentric Fluoroscopy • Combination of ultrasonography and fluoroscopy 24 Dept of Urology, GRH and KMC, Chennai.
  • 25.
    Choice of theideal lithotripter for any given stone center • A multifunctional workstation for SWL and endourologic procedures is the best choice for centers with an adequate patient load in both treatment modalities. • An integrated or hybrid design makes economic sense in very active stone centers. • In centers with a modest patient load a modular system may probably be the better choice 25 Dept of Urology, GRH and KMC, Chennai.
  • 26.
    ESWL-HISTORY • Dornier HMI -1980 • HM II- 1982 • Dornier HM III – 1984 • Portable Dornier – 1996 • Dornier HM IV - 1997 26 Dept of Urology, GRH and KMC, Chennai.
  • 27.
    MECHANISM 27 Dept of Urology,GRH and KMC, Chennai.
  • 28.
    Traditional theories ofstone fragmentation • stress gradient and tensile failure at stone/ fluid boundaries • Acoustic cavitations • Squeezing Compression fracture • quasi‐static squeezing(wide focus with lower pressure to enhance) • Hopkins effect (cavitation and shear forces) • Spallation • Dynamic fatigue • dynamic squeezing 28 Dept of Urology, GRH and KMC, Chennai.
  • 29.
    29 Dept of Urology,GRH and KMC, Chennai.
  • 30.
    30 Dept of Urology,GRH and KMC, Chennai.
  • 31.
    Spallation • Reflected tensilewave at distal surface of the stone with maximum tension at the distal part of the stone • Spalling will gradually become less effective as the size of fragments decreases or in stones with curved boundaries or when wave attenuation in the stone material is high • Breaking the stone from the inside 31 Dept of Urology, GRH and KMC, Chennai.
  • 32.
    Tear and shear •Pressure gradients resulting from impedance changes at the stone front and distal surface with pressure inversion • Stone made of layers • Hammer-like action resulting in a crater-like fragmentation 32 Dept of Urology, GRH and KMC, Chennai.
  • 33.
    Quasi-static squeezing • Pressuregradient between circumferential and longitudinal waves results in squeezing of the stone • Nutcracker-like action 33 Dept of Urology, GRH and KMC, Chennai.
  • 34.
    cavitation • Cavitation isdefined as the formation and collapse of bubbles • Negative pressure waves induce a collapsing cavitation bubble at the stone surface • Microexplosive erosion at the proximal and distal ends of the stone 34 Dept of Urology, GRH and KMC, Chennai.
  • 35.
    Dynamic squeezing • Shearwaves initiated at the corners of the stone and driven by squeezing waves along the calculus lead to the greatest stress and tension • Nutcracker-like action in combination with spalling 35 Dept of Urology, GRH and KMC, Chennai.
  • 36.
    • squeezing willbe enhanced when the entire stone falls within the diameter of the focal zone • If lithotripters have very small focal zones this mechanism will be ineffective 36 Dept of Urology, GRH and KMC, Chennai.
  • 37.
    SUPERFOCUSING Shockwave passed into stone get reflected at the distal surface of the stone focused either by refraction or by diffraction from the corners of the stone to interior of stone fragmentation 37 Dept of Urology, GRH and KMC, Chennai.
  • 38.
    38 Dept of Urology,GRH and KMC, Chennai.
  • 39.
    39 Dept of Urology,GRH and KMC, Chennai.
  • 40.
    Unified mechanism 40 Dept ofUrology, GRH and KMC, Chennai.
  • 41.
    A heuristic modelof stone comminution in SWL 1. P+(avg) (controlled by the output kV or energy setting of the lithotripter) and 2 .dose of the shock waves delivered • Effective treatment can be achieved by using moderate P+(avg) in the range of 15–20 MPa within 2000 shocks. • progressive ramping of the lithotripter output (and thus P+(avg)) that can achieve effective stone comminution with minimal risk of tissue injury 41 Dept of Urology, GRH and KMC, Chennai.
  • 42.
    42 Dept of Urology,GRH and KMC, Chennai.
  • 43.
    AIM • Fragment thestone to 1mm pieces- IDEAL • <= 4 mm acceptable • Clearance may take 3-4 weeks,varies among patients 43 Dept of Urology, GRH and KMC, Chennai.
  • 44.
    CONTRAINDICATION • Urinary TractInfection • Pregnancy • Uncorrected Coagulopathy • Arterial aneurysms in close proximity to target stone • Uncontrolled hypertension • Distal obstruction • Morbid Obesity • Spinal Deformity or Limb Contractures 44 Dept of Urology, GRH and KMC, Chennai.
  • 45.
    SWL TREATMENT OFRENAL AND URETERAL CALCULI RENAL CALCULI • To achieve maximal stone clearance with minimal morbidity 45 Dept of Urology, GRH and KMC, Chennai.
  • 46.
    INDICATION • Pain • Infection •Obstruction 46 Dept of Urology, GRH and KMC, Chennai.
  • 47.
    Stone size andlocation • SWL stone‐free rates at 3 months are 86–89% for renal pelvis, 71–83% for upper calyx, 73–84% for middle calyx, and 37–68% lower calyx stones • 10 mm or less - 74% ( 60 to 90%) • 11 to 20 mm - 54% ( 50 to 83%) • >20 mm - 33% ( 33 to 81%) 47 Dept of Urology, GRH and KMC, Chennai.
  • 48.
    48 Dept of Urology,GRH and KMC, Chennai.
  • 49.
    SMALL, ASYMPTOMATIC CALYCEAL STONES(<5mm) Controversial Most calyceal stones, in the absence of intervention, are likely to increase in size, causing symptoms of pain or infection prophylactic SWL - targeting may be difficult Indication pediatric patients solitary kidney High-risk professions ( pilots) Women considering pregnancy 49 Dept of Urology, GRH and KMC, Chennai.
  • 50.
    TREATMENT DECISIONS BYSTONE COMPOSITION • Fragmentation by SWL is variable among stones of different composition • Cystine • Brushite calculi • Calcium oxalate monohydrate • matrix • most resistant to SWL, produce large pieces that may be difficult to clear from the collecting system 50 Dept of Urology, GRH and KMC, Chennai.
  • 51.
    • Brushite, cystine,calcium oxalate monohydrate should be treated by SWL only when the stone burden is small (<1.5 cm) • Larger stones -- PNL or ureteroscopy • Matrix calculi • Radiolucent ,associated with urea-splitting bacteriuria • SWL is not effective (gelatinous nature ) • PNL , ureteroscopy – choice 51 Dept of Urology, GRH and KMC, Chennai.
  • 52.
    PREDICTION OF STONECOMPOSITION (STONE FRAGILITY) • PLAIN X-RAY KUB - smooth-edged stones, homogeneous, more dense than bone -- require more shockwaves • Round, radially reticulated stones with spiculated edges or stones with irregular margin – good fragmentation • Accuracy - 39% 52 Dept of Urology, GRH and KMC, Chennai.
  • 53.
    • NON–CONTRAST-ENHANCED HELICALCT • basis of attenuation values • success rate - lower for calculi with attenuation values greater than 1000 Hounsfield units • Distinguish stone types • Uric acid from calcium stones 53 Dept of Urology, GRH and KMC, Chennai.
  • 54.
    Hounsfield density • CTattenuation values are greater than 900–1000 HU • Skin‐SSD was measured by averaging the distance between the center of the stone 54 Dept of Urology, GRH and KMC, Chennai.
  • 55.
    Predictive models ofshock‐wave lithotripsy success 55 Dept of Urology, GRH and KMC, Chennai.
  • 56.
    Preoperative considerations • Antibioticprophylaxis • in the absence of urinary tract infections or other risk factors ,antibiotic prophylaxis prior to SWL is not indicated 56 Dept of Urology, GRH and KMC, Chennai.
  • 57.
    DJ STENTING • stone‐freerate in those who were stented preoperatively was 78.1 versus 83% in the stentless group (P = 0.27). • The presence of a stent also does not prevent renal colic, steinstrasse, or additional procedures • Current guidelines no longer recommend routine preoperative stenting 57 Dept of Urology, GRH and KMC, Chennai.
  • 58.
    INDICATIONS FOR STENTING •Large stone burden >1.5 cm • Obstructed system • Pyonephrosis • Poorly visualised stones 58 Dept of Urology, GRH and KMC, Chennai.
  • 59.
    INTRA-OPERATIVE DETAILS • noconclusive data to recommend an optimum number of shock waves(2000–3000 shock waves) • 60-90 shocks / min • Negative pressure phase of a shock wave becomes dampened at a faster rate(responsible for cavitation bubbles) • benefits of a slower shockwave rate are most notable for stones >10 mm 59 Dept of Urology, GRH and KMC, Chennai.
  • 60.
    Pretreatment • application oflow‐energy shock waves to the targeted renal stone in order to “prime the kidney” and reduce renal injury( associated with renal vasoconstriction) • 300 -500 shock waves applied at 12 kV proven to significantly reduce the hemorrhagic lesion size(20 times!) • 3-4 min pause also decreases hemorrahge 60 Dept of Urology, GRH and KMC, Chennai.
  • 61.
    SHOCK WAVE ADMINISTRATION •Voltage – 12 - 24kV • Power – 100- 120 Hz • Number of shock waves – 60-90/min • Sequence of shock wave delivery – Step wise power ramping – shock wave intensityis gradually increased – Two -Step power ramping – (Low to High) – 100 waves at 18kV followed by 2000 waves at 24kV 61 Dept of Urology, GRH and KMC, Chennai.
  • 62.
    Renal Stone • nonstaghorn – ideal 6-10mm • 10-20mm in the absence of other factors • >20mm not recommended 62 Dept of Urology, GRH and KMC, Chennai.
  • 63.
    RENAL ANATOMIC FACTORS •Ureteropelvic junction obstruction • Horseshoe kidney • Ectopic or fusion anomalies • Calyceal diverticula 63 Dept of Urology, GRH and KMC, Chennai.
  • 64.
    Lower pole stones •Less than 10mm ESWL • 10-20mm –infundibulopelvic angle more than 70deg, infundibular width more than 4mm,infundibulum length less than 3cm are favourable. • More than 20mm PCNL 64 Dept of Urology, GRH and KMC, Chennai.
  • 65.
    PUJ obstruction,megaureter, duplicatedureter with hydronephrosis Renal scintigraphy should be considered to rule out clinically significant obstruction. Three month stone‐free rates for these anatomical variations in those without obstruction range from 40–55% CALICEAL DIVERTICULAM SWL - Stone-free rates are low (0-25%) May be useful for stones <1 cm in size only if there confirmed, short and patent diverticular neck which could allow fragment passage URINARY DIVERSION colon conduits is 3–4% and with ileal conduits is 10–20% SWL monotherapy was found to have an 81.5% success 65 Dept of Urology, GRH and KMC, Chennai.
  • 66.
    66 Dept of Urology,GRH and KMC, Chennai.
  • 67.
    CARDIAC PATIENTS • GatedLithotripsy(at R wave) • Pace makers – guarded procedure • rotating the patient 15–20° 67 Dept of Urology, GRH and KMC, Chennai.
  • 68.
    CHILDREN • SWL forstones >2 cm in size, including staghorn calculi, can be effective and is acceptable in children • Lung protection – Styrofoam paddings • Low kV and No. of shocks • Exit site shielding with wet towels –decreased echymosis 68 Dept of Urology, GRH and KMC, Chennai.
  • 69.
    Adjunct therapy aftershock‐wave lithotripsy • to improve stone clearance after SWL, especially for lower pole stones • Involve drinking500 ml of water 30 minutes prior to inversion in a proneTrendelenburg position at 45° and continuous manual mechanical percussion over the flank for 10 minute 69 Dept of Urology, GRH and KMC, Chennai.
  • 70.
    Medical therapy aftershock‐wave lithotripsy • α‐adrenergic antagonists • phyllanthus niruri, a Brazilian plant remedy which prevents calcium oxalate crystal • potassium citrate 70 Dept of Urology, GRH and KMC, Chennai.
  • 71.
    Follow‐up after SWL •No consensus on follow‐up imaging after SWL. • Obtaining plain Xray KUB 1–4 weeks after SWL • Document SWL failure as being after three sessions • Offer endoscopic therapy as the next treatment option in those who fail a single session 71 Dept of Urology, GRH and KMC, Chennai.
  • 72.
    ESWL FAILURE • PCNL •RIRS • SANDWICH • OPEN STONE SURGERY 72 Dept of Urology, GRH and KMC, Chennai.
  • 73.
    Ureteric stone • Proximalureteric stones<1cm ESWL insitu • SSD cutoff of 11–12 cm • 70–97% for proximal stones, 58–97.8% for mid‐ureteral stones, and 54–97.9% for distal ureteral calculi • Impacted stones are resistant 73 Dept of Urology, GRH and KMC, Chennai.
  • 74.
    ESWL & URETERICCALCULI • For fragmentation fluid medium around stone necessary • If stones impacted fragmentation may not occur • “PUSH & BANG”-success Marginally HIGHER THAN “in situ ESWL” 74 Dept of Urology, GRH and KMC, Chennai.
  • 75.
    • rotating thepatient toward the therapy head increased the success rate significantly for mid‐ and distal ureteral calculi (from 83.9 to 95% and from 89.1 to 98.0% respectively) and a significant decrease in number of SWL sessions for proximal stones 75 Dept of Urology, GRH and KMC, Chennai.
  • 76.
    Ureteric stone 76 Dept ofUrology, GRH and KMC, Chennai.
  • 77.
    • Factor forspontaneous passage of stone • Width of the stone • Location • Width of the stone • Stones < 4 mm -- rates of spontaneous passage of 80% • 4 to 6 mm -- 59% • > 6 mm – 21% • Location • Proximal -- 22% • Middle -- 46% • Distal ureter -- 71% • Stones of 5 mm or less, conservative management 77 Dept of Urology, GRH and KMC, Chennai.
  • 78.
    Complication of eswl •Hematuria most common,resolves within a few hours. • effect in vessels can be differentiated by measuring α2‐ macroglobulin enhancement found immediately after and 1 day following SWL • Detoriation of renal function • Renal colic 78 Dept of Urology, GRH and KMC, Chennai.
  • 79.
    Complications • Steinstrasse • (Coptcoat’sclassification of steinstrasse exists (Type I, fragments <2 mm in diameter; Type II, leading fragment 4–5 mm tailed by 2 mm particles; and Type III,consisting of large fragments), • Infectious complications: 5.1% in spite of preoperative sterile urine. MC Escherichia coli 79 Dept of Urology, GRH and KMC, Chennai.
  • 80.
  • 81.
    EXTRARENAL INJURY • Liver •skeletal muscle – pain at site of entry • Gastric and duodenal erosion • Lung parenchyma • Acute pancreatitis • Hematochezia - mucosal damage of the colon • Myocardial infarctions, cerebral vascular accidents • cardiac arrhythmia 11and 59% during ungated SWL • Sperm count 81 Dept of Urology, GRH and KMC, Chennai.
  • 82.
    • ACUTE RENALINJURY • Structural • Functional • Hemorrhage and edema within or around the kidney • Intrarenal edema ,Subcapsular hematoma (3% - 12%) • 6 weeks - 24 months to resolve 82 Dept of Urology, GRH and KMC, Chennai.
  • 83.
    2,000 shocks at12 (A), 18 (B), 24 (C) Kv subcapsular hematona increases with increasing kV level 83 Dept of Urology, GRH and KMC, Chennai.
  • 84.
    Bilateral perinephric hematomas followingbilateral simultaneous ESWL 84 Dept of Urology, GRH and KMC, Chennai.
  • 85.
    • CHRONIC RENALINJURY • Structural • Functional • chronic renal changes - due to scar formation • Accelerated rise in systemic blood pressure • Decrease in renal function • Increase in the rate of stone recurrence (residual stone debris) 85 Dept of Urology, GRH and KMC, Chennai.
  • 86.
    • CHRONIC HISTOLOGICCHANGES • Nephron loss • Dilated veins • Diffuse interstitial fibrosis • Calcium and hemosiderin deposits • Hyalinized and acellular scars from cortex to medulla 86 Dept of Urology, GRH and KMC, Chennai.
  • 87.
    Steinstrasse ( orStone Street) – Post ESWL 87 Dept of Urology, GRH and KMC, Chennai.
  • 88.
    Factors influencing renaltrauma • No of shocks 500-8000 • Period of shock wave, decreased period increased damage • Kidney size • Children • Preexisting RD • Scarring 2% in adults &7% in children • Lithotripter output settings such as output energy and energy flux density, total number of shocks, • pre‐existing hypertension in older 88 Dept of Urology, GRH and KMC, Chennai.
  • 89.
    Damage control • Useof low power.12-15 kv • Priming of kidney • Treat at slow shock wave rate- 1 S W per sec. • Sedation. • Number of shock waves to be less • Maximum session 3-5.interval bt session 10- 14 days. 89 Dept of Urology, GRH and KMC, Chennai.
  • 90.
    Dornier HM-3 90 Deptof Urology, GRH and KMC, Chennai.
  • 91.
    Siemens Lithostar lithotriptor91 Dept of Urology, GRH and KMC, Chennai.
  • 92.
    LithoDiamond with portableC-arm (modular designs) 92 Dept of Urology, GRH and KMC, Chennai.
  • 93.
    • TANDEM-PULSE LITHOTRIPTER •Lithotripter with auxiliary piezoelectric head to generate a second shock wave along the same acoustic axis • Two shock waves are used in rapid succession to drive forceful collapse of bubbles against stone • DUAL PULSE LITHOTRIPSY • Two lithotriptor generate pulses,released simultaneously, both focused at the same F2 - minimize cavitation • 93 Dept of Urology, GRH and KMC, Chennai.
  • 94.
    Dual pulse lithotripsy. Coaxiallyaligned electrohydraulic shock wave sources with a common F2 94 Dept of Urology, GRH and KMC, Chennai.
  • 95.
    95 Dept of Urology,GRH and KMC, Chennai.