ESWL

1. ESWL
MECHANISM
ROLE IN CURRENT PRACTICE
DR J KIRAN KUMAR
RESIDENT UROLOGY MMC CHENNAI

2. ESWL
• In extracorporeal shock wave lithotripsy (SWL) a source external to
the patient's body generates a shock wave.
• Shock waves are surfaces that divide material ahead, not yet
affected by the disturbance from that behind, which has been
compressed as a consequence of energy input at the source.

3. Historic perspective
• In 1963physicists at Dornier, an aircraft manufacturer in Friedrichshafen,
Germany, had investigated the impactof raindrops on flying objects, as these
impacts caused shock waves which not only damaged the outer shell of airplanes
but also structures within.
The first lithotriptor for human treatment, the Dornier Human
Model 1 or HM1, was built in the year 1979.
• The first patient was successfully treated using a Dornier
HM1 on 7 February 1980 by Christian Chaussy, B.
Forssmann, and D. Jocham.

4. • In 1983-the second lithotripsy center was opened in the Department
of Urology (F. Eisenberger) of the Katharinen Hospital in Stuttgart.
• In March 1984 the firstDornier HM3 in the United States was installed
in the Methodist Hospital in Indianapolis.

5. LITHOTRIPTER GENERATIONS
• First generation lithotripters -large water bath plus electrohydraulic
shock wave source
• Second‐generation lithotripters utilize an
electrohydraulic,electromagnetic, or piezoelectric shock‐wavesource.
Transmission of the shock wave is provided bymeans of a water
cushion or partial water bath.
• Third‐generation lithotripters are also equipped with an
electrohydraulic, electromagnetic, or piezoelectricshock‐wave source.
All systems allow anesthesia‐free treatments

6. • Shock wave behavior is characteristic of thepropagation of nonlinear
waves.
• The shock wave lithotripter uses weak, nonintrusive waves that are
generated externally, transmitted through the body, and focused
onto the stone.
• The shock waves build tosufficient strength only at the target, where
they generate enough force to fragment a stone.

7. GENERATOR TYPES
• The three primary types of shock wave generators are
electrohydraulic(spark gap)
electromagnetic
piezoelectric

8. Electrohydraulic (Spark Gap) Generator.
• spherically expanding shock wave is generated by an underwater
spark discharge.
• High voltage is applied to two opposing electrodes; the resulting
spark produces a vaporization bubble. The bubble expands and
collapses rapidly producing a high-energy pressure wave.
• The resulting shock wave occurs at F1 (the electrode) located on an
ellipsoid, which focuses the wave on the stone target (F2).

9. An electrode is used to generate a shock wave. F1,
Focus 1; F2, focus

10. • The clear advantage of this generator is its effectiveness in breaking
• kidney stones .
• . Disadvantages are the substantial pressure
• fluctuations from shock to shock.

11. Electromagnetic Generator
• The electromagnetic generators produce a magnetic field in either a
flat plane or around a cylinder.
• The flat plane waves are focused by an acoustic lens
• ;The cylindric waves are reflected by a parabolic reflector and
transformed into a spherical wave.

12. An electromagnetic coil is used to generate the
shock wave. F2, Focus 2.
acoustic lens to focus the shock wave

13. parabolic reflector to focus the shock wave

14. advantages and disadvantages
• more controllabe and reproducible
• less pain
• frequent electrode replacement is less
• increase rates of subcapsular hematoma.

15. Piezoelectric Generator
• The piezoelectric lithotripter also produces plane shock waves with
directly converging shock fronts.
• A capacitor is fired through a collection of several hundred to several
thousand piezoceramic elements positioned on a reflector, often
shaped like a satellite dish .
• Each element produces a limited power shock front that is focused
on the same F2

16. Numerous polarized polycrystalline ceramic
elements are positioned on the
inside of a spherical dish..

17. ADVANTAGES AND DISADVANTAGES
• The advantages of piezoelectric generators include the focusing
accuracy, a long service life, and the possibility of an anesthetic-free
treatmentbecause of the relatively low-energy density at the skin
entry point of the shock wave.
• disadvantage--poor stone comminution{ .the actual energy delivered
to the stone per shock wave is lower}

18. Imaging Systems
• fluoroscopy alone
• ultrasonography alone.
• combination of ultrasonography and fluoroscopy.

19. Fluoroscopy Alone
• The original Dornier HM3 lithotripter used two x-ray converters
arranged atoblique angles to the patient and 90 degrees from each
other to localize the stoneeffectively at F2..

20. • The primary advantages of fluoroscop
• familiarity to most urologists
• , the ability to visualize radiopaque calculi throughout the urinary tract
• , the ability to use iodinated contrast agents to aid in stone localization,
• ability to display anatomic detail.
• The disadvantages include
• exposure of the staff and patient to ionizing radiation
• , the high maintenance demands of the equipment.
• inability to visualize radiolucent calculi without the use of radiographic
contrast agents.

21. Ultrasonography Alone.
• in expensive
• children and adloscent.
• localisation of slightly and non opaque calculi

22. significant disadvantages
• Sonographic localization of a kidney stone requires a highly
• trained operator,
• t it is almost impossible to view a kidney stone in areas such as the
• middle third of the ureter or when there is an indwelling ureteral
catheter.
• once a stone is fragmented, it is difficult to identify each individual
stone piece.

23. Stone Fragmentation
• an initial short and steep compressive front with pressures of
approximately 40 megapascals (MPa)
that is followed by a longer, lower amplitude negative (tensile)
pressure of 10 MPa, with the entire pulse lasting for a duration of 4
microseconds.
ratio of the positive to negative peak pressures is approximately 5 : 1.

25. • Stone fragmentation during SWL, also called comminution, occurs as
a result of mechanical stressors created by two
• mechanisms that can occur simultaneously or separately:
• (1) directly by the incident shock wave
• (2) indirectly by the collapse of bubbles..

26. • The different mechanical stresses that result from SWL and
contribute to stone fragmentation are
• : spall fracture
• , squeezing
• , shear stress
• , superfocusing
• , acoustic
• cavitation,
• dynamic fatigue

28. • Spall fracture, also known as spallation, is the calescence of
microcracks within a stone resulting in comminution
• squeezing-splitting or circumferential compression, occurs because
of the difference in sound speed between the stone and the
surrounding fluid.
• Shear stress will be generated by shear waves (also termed transverse
waves) that develop as the shock wave passes into .the stone.

29. • superfocusing, is the amplification of stresses inside the stone
because of the geometry of that stone.
• Cavitation is the formation and subsequent collapse of bubbles.

30. • The final mechanism of stone fragmentation to be considered is the
accumulation of damage induced by SWL that eventually destroys the
structure of the stone.
range of two orders of magnitude (30 to 3000 shocks).-to comminute
stones

31. • modular design,where all components are independent and
connected according to need,
• integrated design, where all components are integrated in the
machine and ideallyadapted to their function
• . A third design, the “hybrid,”offers integration of imaging and/or
therapy head in a common console with an independent treatment
table.
LITHOTRIPTER DESIGN

32. modular design

33. Integrated design: Dornier
Gemini.

34. Hybrid design: Wolf Piezolith
3000 plus.

35. Performance
of lithotripters
• stone‐free rate,
• retreatment rate
• auxiliary procedure rate.
• effectiveness quotient (EQA) was defined by Denstedt, Clayman and
Preminger

39. ACUTE EXTRA RENAL DAMAGE
• elevated levels of bilirubin, lactate dehydrogenase, serum aspartate
• transaminase, and creatinine phosphokinase within 24 hours of
treatment
• perforation of the colon,
• hepatic hematoma, splenic rupture, pancreatitis, and abdominal wall
abscess.
• rupture of the hepatic artery, rupture of the abdominal aorta, and
iliac vein thrombosis.
• . Thoracic events, such as pneumothorax and urinothorax, have even
• been described.

40. DIABETES MELLITUS
• total number of shock waves and the power level of the lithotripter
• did not find any association between SWL and diabetes mellitus in
the general community setting.

41. ACUTE RENAL INJURY
• hematuria common
consequence of irritation of the
urothelium as stones were fragmented by shock waves,
• damage to the kidney is the most likely source
• Hematoma rates range from less than 1% to as high as 20%, depending on the
• type of lithotripter used and the treatment parameters employed, as well as
the radiographic modality and timing of imaging follow-up.

42. mechanism for tissue injury
• once blood vessels have been ruptured and blood has
• collected in pools, there is a greater potential for cavitation to occur.
• pooling of blood provides a large fluid-filled space for cavitation
bubbles to grow and collapse.

43. post swl hematoma risk factors
• Age
• Obesity
• Coagulopathies
• Thrombocytopenia
• Diabetes mellitus
• Coronary heart disease
• Preexisting hypertension
• Body mass index >30 or <21.5

44. long term concerns
• hypertension - no evidence
• chronic kidney disease-no evidence
• diabetes mellitus-no evidence
• stone recurrence-association
• male infertility-decrease for distal ureteral stoned normalizes by 3
months
• female infertility-inconcllusive

45. • based on the current literature, there is no evidence to indicate SWL
is associated with long-term renal dysfunction.

46. OPTIMIZE SWL OUTCOME
• Aggravating Factors
• Number of shocks
• Period of shock wave administration: Shorter period increases
damage
• Accelerating voltage: Higher voltage increases damage
• Type of shock wave generator: First- versus second-/third-generation
• devices
• Kidney size: Juvenile versus adult
• Preexisting renal impairment

47. • Mitigating Factors
• Pretreatment with 100 to 500 shocks at low energy level to reduce
lesion
• size
• Treatment at a slow rate of shock wave delivery (≤60 shocks/min)

48. IMPROVE SWL OUTCOMES
• Appropriate coupling
• Water-soluble lubricant applied by hand
• Decrease rate to low (60–70 shocks/min) or intermediate (80–90
• shocks/min)
• Image frequently and stop shocking once fragmented
• Do not use a preset number of shocks
• Ramping protocol
• Treat with low power escalating to higher levels
• General anesthesia
• Do not use a ureteral stent
• Consider alpha-blockers for medical expulsive therapy
• Consider percussion, diuresis, inversion therapy

49. • slowing the shock wave delivery rate to less than 120 SW/min
improves stone fragmentation
• Cavitation is thought to play a role in improved results at
lower SWL rates, because the dynamic bubbles are given a longer
timeinterval to dissipate with a slower rate.
• At a higher rate the bubbles build on the surface of the stone forming
a barrier to SW energy transmission and thus act as an energy draw
from subsequent shocks .

50. • The discomfort experienced during SWL is related directly to the
energy density of the shock wave as it passes through the skin and
the size of the focal point.

51. • Currently, theAmerican Urological Association (AUA) guidelines do not
recommend the placement of ureteral stents at the time of SWL
because stent placement has not been shown to improve stone
passage rates and only increases patient morbidity.

52. PDI THERAPY
• The general concept is some type of diuretic—either drinking copious
amounts of fluid or taking a diuretic agent (e.g., furosemide)—is
employed and the patient is placed in a prone Trendelenburg
position while the flank is percussed for approximately 10 minutes.

53. FUTURE DIRECTION
• The Visio-Track (VT) locking system has the potential to increase stone
• fragmentation rates and decrease fluoroscopy time.
• The VT is a hand-held probe with an infrared stereovision, which
allows triangulation of the stone location.
• The VT is used with ultrasound-guided lithotripters and allows the
lithotripter to “lock on” to the stones location during treatment.

54. • Ultrasonic propulsion of renal and ureteral calculi is another measure
thought to potentially improve outcomes with SWL.
• Focused ultrasound has emerged as a technology that can expel
small stones or stone fragments from the urinary system .

56. Shock‐wave Lithotripsy of Renal Calculi
• Preoperative
• evaluation
• urine analysis
• urine culture
• pregnancy tests
• coagulation profile
• renal usg/x ray kub

57. Absolute
contraindications
• Pregnancy
• Uncontrolled bleeding diathesis
• Uncontrolled hypertension
• Untreated infection
• Significant skeletal malformations or severe obesity
• Arterial aneurysms in close proximity to target stone

58. Stone characteristics

59. Imaging characteristics
• Hounsfield density, pelvicalyceal anatomy,
• and skin‐to‐stone distance are only available with
• CT imaging.

60. Stone size and location
• stones >2 cm in the upper and middle calyces and >1 cm
• in the lower calyx should not be offered SWL as first‐line
• therapy

61. Steinstrasse
• Incomplete fragmentation can lead to steinstrasse,which is a column of stone fragments
that lodge withinthe ureter causing obstruction after SWL.
• The word steinstrasse is German for “stone street” whichrefers to the radiographic
appearance of this condition.
• Steinstrasse occurs when the lithotripter fragments the stone into pieces that are not
easily passed spontaneously
• . Size and location are two independent risk factors for this to occur.
• SWL performed on renal stones is 2.7 times more likely to cause steinstrasse
than ureteral stones.
• Incidence rates for steinstrasse after SWL for renal stones <1, 1–2, and >2 cm were 4.4,
15.7, and 24.3%, respectively.

62. 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
• Type III,consisting of large fragments

63. Lower pole pelvicalyceal anatomy
• acute infundibulopelvic angle, shorter infundibular
• length, and increased infundibular width of the lower
• pole as being associated with increased likelihood of
• stone clearance
• infundibulopelvic angle >90°, infundibular length
• <3 cm, and infundibular width >5 mm were all significant
• predictors of stone‐free status

65. Hounsfield density
• SWL should not be considered when
• CT attenuation values are greater than 900–1000 HU
• CT attenuation values <970 HU correlating with a
• 96% success rates
• 62% of patients above that threshold
• failed treatment

66. Skin‐to‐stone distance
• SSD was measured by averaging
• the distance between the center of the stone and
• the skin at 0, 45, and 90° from a horizontal line drawn
• through the stone on axial CT images
• An SSD cutoff of 10 cm is associated
• with the optimal sensitivity and specificity

68. TRIPLE D SCORE
• SSD (distance), stone attenuation
• (density), and ellipsoid stone volume (ESV) (dimensions)
• To determine the Triple D score, a point is
• added when ESV is <150 μl, stone attenuation is <600 HU,
• or SSD is <12 cm

69. Routine preoperative stenting
• The presence of a stent also does not prevent renal colic,
steinstrasse, or additional procedures
• Current guidelines
no longer recommend routine preoperative stenting
• can be considered for renal stones >2 cm

70. Shock‐wave number and rate
• most surgeons apply 2000–3000 shock waves
• Stones treated at the lower rates of 75 and 150 shocks/minute
achieved better fragmentation
• RCTs have shown that optimal SWL frequency is 60–90
shocks/minute

71. Medical therapy after shock‐wave lithotripsy
• α‐adrenergic antagonists, calcium channel
blockers, corticosteroids, and smooth muscle relaxants
• Phyllanthus niruri, a Brazilianplant remedy which prevents calcium
oxalate crystal growth, was shown to improve stone‐free rates after
SWL of lower pole stones when compared with placebo in a RCT.

73. Pediatric
shock‐wave lithotripsy
• SWL for stones >2 cm in
• size, including staghorn calculi, can be effective and is
• acceptable in children
• For larger and staghorn stones in
• children, preoperative stent or nephrostomy decreases
• SWL complications

74. Current
indications for shock‐wave
lithotripsy of ureteral stones
• 70–97% for proximal stones, 58–97.8% for mid‐ureteral
• stones, and 54–97.9% for distal ureteral calculi
• SWL as first‐choice for proximal stones <10 mm and no
• preference of SWL or ureteroscopy for distal stones
• <10 mm

75. Patient positioning
• Different possible positions for targeting a distal ureteral stone. (a)
Supine vertical therapy head, (b) supine oblique therapy
• head, (c) modified supine, oblique therapy head, (d) prone, vertical
therapy head, (e) prone, oblique therapy head, from ipsilateral side,
• (f ) prone, oblique therapy head from contralateral side, (g) modified
prone, oblique therapy head from ipsilateral side, (h) supine,
• over‐patient vertical therapy head, and (i) prone, over‐patient oblique
therapy head, from contralateral sid

76. treatment protocol suggestions
• For stones >10 mm, use a shock‐wave rate of 60–90
shocks/minute (1–1.5 Hz)
• Low‐voltage pretreatment with approximately 300
shocks for proximal ureteral stones (especially if
renal parenchyma is in the blast path of the shock
wave)
• A treatment pause has no proven benefit
• In treatment of mid‐ureteral to distal stones under
conscious sedation or general anesthesia, voltage
ramping may be omitted.

77. Complications of Shock‐wave Lithotripsy
• Hematuria
• Detoriation of renal function
• Renal colic (manageable conservatively)

78. • Hematuria following SWL is one of the most common findings
• usually resolves within a few hours
• The effect in vessels can be differentiated by measuring α2‐
macroglobulin enhancement found immediately after and
1 day following SWL

79. Colic needing intervention
• Insertion of double‐J stent or percutaneous nephrostomy tube is
indicated in cases complicated by urinary tract infection
• INFECTIOUS COMPLICATIONS
• The most common pathogens were Escherichia coli (35.1%),
• Pseudomonas aeruginosa (16%), Klebsiella pneumoniae
(12.8%), Proteus mirabilis (11.7%), Enterococcus faecalis
(8.5%), and Enterobacter cloacae (4.3%).
• No standard antibiotic prophylaxis before SWL is recommended

80. Cardiovascular complications
• The incidence of morbid cardiac events or biochemical
• myocardial injury is extremely rare
• The SWL treatment in patients with aortic aneurysm is
• controversial
• aneuryma in the vicinity of the stone and focal zone of
SWL remain a contraindication for SWL treatment.

81. Gastrointestinal complications related
to SWL treatment
• Gastric and duodenal erosions recorded by pre‐ and
• post‐ESWL endoscopy was found in 80% of the patients
• Ureterocolic fistula
• Hepatic hematoma and spleen hematoma are rare
complications of SWL
• Elevation of serum amylase and lipase is presented in
patients with acute pancreatic trauma

82. Long‐
term effects
• DIABETES MELLITUS-statistical association of SWL
with new‐onset of DM could not be found in the overall
analysis
• Effect on reproduction organs and pregnancy-SWL does not affect
female fertility or lead to increased teratogenic risk
• HYPERTENSION-NO CLEAR ASSOCIATION FOUND

83. THANK YOU SIRS