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Extracorporeal Shock Wave Lithotripsy in a Nutshell

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Christian Chaussy, Geert Tailly, Bernd Forssmann, Christian Bohris, Andreas Lutz, Martine Tailly-Cusse, Thomas Tailly

Edited by Christian Chaussy and Geert Tailly Steinzertruemmerer_A5_EN_20150929.indd 1

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Extracorporeal Shock Wave Lithotripsy in a Nutshell Christian Chaussy Geert Tailly Bernd Forssmann Christian Bohris Andreas Lutz Martine Tailly-Cusse Thomas Tailly

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Christian Chaussy Prof. of Urology University of Regensburg, Germany cgchaussy@gmail.com Geert G. Tailly, MD, FEBU Head of the Department of Urology AZ Klina, Brasschaat, Belgium geert.tailly@klina.be Bernd Forssmann, Dr. Herrsching, Germany Christian Bohris, Dr. Project Leader, Dornier MedTech Systems GmbH, Wessling, Germany Andreas Lutz, Dr. Director Product Development, Dornier MedTech Systems GmbH, Wessling, Germany Martine Tailly-Cusse Specialty nurse Endourology & ESWL AZ Klina, Brasschaat, Belgium Thomas Tailly, MD Department of Urology, UZ Ghent , Belgium Š Dornier MedTech Europe GmbH Published by Dornier MedTech Europe GmbH Argelsrieder Feld 7 82234 Wessling Germany http://www.dornier.com Printed by Dinauer GmbH, Munich, Germany 2nd and revised edition

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V

Inhalt 1 Introduction

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2 2.1 2.2 2.3 2.4

Lithotripter design Shock wave generator Localization system Patient positioning Integrated endourology concept

3 3.1

Basics of shock wave physics 13 Shock wave generation 14 3.1.1 Electromagnetic 14 3.1.2 Electrohydraulic 14 3.1.3 Piezoelectric 14 Shock wave parameters 15 3.2.1 Pressure P+ 15 3.2.2 Focus size 16 3.2.3 Penetration depth 17 3.2.4 Effective energy E12mm 17 3.2.5 Energy flux density 17 Energy dose 18 Stone breaking mechanisms 19 3.4.1 Hopkinson effect 19 3.4.2 Shear forces 20 3.4.3 Squeezing effect 20 3.4.4 Cavitation 21 Tissue effects 21

3.2

3.3 3.4

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4 Indications 4.1 Renal stone treatment 4.1.1 General recommendation 4.1.2 Special recommendation for lower pole stones 4.2 Ureteral stones 4.3 Special indications 4.3.1 Paediatric urolithiasis 4.3.2 Obesity 4.3.3 Renal anomalies 4.4 Stone composition

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9 9 10 10 11

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VI Contents 5 Contraindications

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6 How to perform ESWL? 6.1 Device preparation 6.2 Pain management 6.3 Patient preparation 6.4 Positioning 6.5 Stone targeting 6.5.1 X-ray guided ESWL 6.5.2 Ultrasound guided ESWL 6.6 Coupling 6.7 Shock wave application – treatment parameters 6.7.1 Kidney stones 6.7.2 Ureteral stones 6.8 Paediatric urolithiasis 6.8.1 Anesthesia 6.8.2 Paediatric positioning aid 6.8.3 Lung protection 6.8.4 Imaging 6.8.5 Adapted shock wave parameters

31 31 32 33 34 35 36 37 40 43 43 44 45 45 45 46 46 46

7 Follow-up 7.1 Stone clearance 7.2 Stone analysis – prevention of new stone formation 7.3 Complications 7.3.1 Renal haematoma 7.3.2 Septicaemia 7.4 Long-term complications

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8 Summary

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9 Literature

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1 Introduction Following extensive research that started as early as in 1974, the first extra­corporeal shockwave lithotripsy (ESWL) treatment of a human was performed on February 07, 1980 by Christian Chaussy, Dieter Jocham and Bernd Forssmann using a prototype Dornier HM1 (Dornier Human Model 1, see Fig.1-1) lithotripter [1]. The first serial Dornier HM3 (Dornier Human Model 3) was installed in 1983 at the Katharinen Hospital in Stuttgart and in March 1984 the first Dornier HM3 in the US was installed at the Methodist Hospital in Indianapolis. The results with this new treatment modality were so successful, that it thoroughly revolutionized modern stone management.

A rapid expansion of indications encompassing urinary stones of all sizes at all levels of the urinary tract made ESWL the treatment of choice for almost any urolithiasis.

Fig. 1-1: HM1 at the Munich University Hospital Grosshadern

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1 Introduction

Primarily due to the high capital investment for a Dornier HM3 ESWL originally remained the privilege of high volume stone centers with urologists heavily trained in the practice of ESWL. With the introduction of less expensive second and third generation lithotripters the practice of ESWL became available to more and also smaller centers. This rapid propagation of extracorporeal shockwave lithotripsy in ever smaller centers inevitably resulted in dilution of experience and poorer results with ESWL. As the newer lithotripters also proved easier to operate than the Dornier HM3, they were considered “plug and play� and proper training in ESWL more often than not was neglected leading to a further deterioration in results. As a consequence the pendulum swung in favour of endoscopic techniques (URS, RIRS, PNL).

Although these techniques demand a high level of skill and expertise, these were and still are provided in extensive and intensive training programs. This is in sharp contrast to the often substandard training in ESWL, still the least invasive treatment modality for any urinary stone. With proper equipment, an understanding of the basic physics of shock waves and adequate training in the safe application of shock wave energy, results are excellent with minimal complications. In order to achieve optimal treatment results with ESWL, an understanding of the underlying physical mechanisms and a knowledge of the necessary treatment protocols are therefore essential. The purpose of this brochure is to inform the user about the physical principles behind the technology and to offer practical guidance on performing ESWL.

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2 Lithotripter design All lithotripters basically consist of three components: a shock wave generating system, a localization system for identifying and localizing the stone and a positioning system used to position the stone in the shock wave focus, where the shock wave intensity is the highest. When the three components are used in the right combination, the stone can be fragmented. Next to these three essential systems, additional components for controlling, monitoring and documentation (Fig. 2-1) are incorporated in most models.

2.1 Shock wave generator The shock wave generator, the most important component of any lithotripter, generates the shock waves and aims them at the focus by means of a focussing unit, such as a lens. Water is necessary to efficiently transfer the shock waves into the patient as it has acoustic properties similar to those of tissue. In the HM3, coupling between the generator and the tissue is achieved directly by means of a water bath in which the patient is placed. This coupling is ideal because there are no disturbing structures to inhibit the propagation of shock waves. In the new units, the shock waves are transferred into the patient via a coupling cushion. For ESWL to be successful the coupling must be loss-free.

Shock wave energy is a key parameter in stone disintegration, while energy flux density relates to the cause of renal side effects. Therefore, the new systems are optimized for high energy in order to deliver the maximum level of energy to the stone with minimal tissue trauma. Today, most lithotripters are equipped with electromagnetic shock wave systems (detailed information is provided in chapter 3).

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2.2 Localization system

2.2 Localization system

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Precise three-dimensional localization of the stone is essential for successful ESWL. Fluoroscopy is the preferred method for locating radiopaque stones in the upper urinary tract and is easily learned. However, it has the disadvantage that continuous observation is not possible because of the associated radiation exposure. Therefore, fragmentation cannot be monitored continuously. In the case of radio-lucent stones, additional measures, such as the use of contrast agents, are necessary. The fluoroscopy is performed using an isocentric C-arm containing a high-powered tube and the imaging system, such as a flat-panel detector. This C-arm can be pivoted longitudinally or orbitally around the shock wave focus in order to view the stone in two planes. The position of the stone can be accurately determined in three dimensions using this information.

Ultrasound is a method that allows the stones to be localized without ionizing radiation, regardless of their composition. The position of the stone in relation to the focus can be monitored and evaluated continuously. However, ultrasound is only satisfactory with stones located in the kidney and in the proximal and distal area of the ureter. It requires a relatively long training period in order to achieve the experience that is needed for successful ultrasound guided ESWL. Both imaging methods can be used simultaneously in most modern lithotripters. In outline localization, the ultrasonic transducer can be moved isocentrically about the focal point in order to set the optimal window for the image. When the ultrasonic transducer is localized in-line, it is located within the shock wave generator along the shock wave propagation axis.

2.3 Patient positioning In order to achieve sufficient disintegration, the stone must first be positioned precisely in the shock wave focus. This is accomplished by using an x-raytransparent table on which the patient can be moved in all spatial axes. The table contains openings that make it possible to couple the shock wave generator to the patient.

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2 Lithotripter design

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Fig. 2-1: Modern urological workstation for ESWL and endourology (Dornier Gemini).

Shock wave unit (a), patient positioning system (b), X-ray localization system with C-arm (c), Flat Panel Detector (FPD) (d) and X-ray tube (e), isocentric ultrasonic localization arm (f).

2.4 Integrated endourology concept Modern stone management is based on a judicious combination and integration of ESWL and endoscopic techniques: the Integrated Endourology Concept. Therefore, modern lithotripters are designed as multifunctional urological workstations that provide optimal conditions for both ESWL and endourolgical procedures, such as URS, PNL, RIRS [2].

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3 Basics of shock wave physics Shock waves are acoustic waves. These waves consist of pressure and density variations, which propagate at medium-specific velocities in media like water and soft tissue as well as in solid bodies such as bones and metals.

In the simplest case, an acoustic wave is a periodic sinusoidal oscillation (See Fig. 3-1).

Fig. 3-1: Schematic illustration of a longitudinal wave. The curve represents pressure or density as a function of space. In a homogeneous medium the waves produce areas of periodic compression and decompression. This is illustrated by the distribution of volume elements showing dense and expanded regions.

When the oscillation is limited to a short duration comprising only a few signal periods, it is called an acoustic pulse. Typical examples are diagnostic ultrasound pulses.

Shock waves are very short acoustic pulses with very short rise times and a high peak pressure.

For details on shock wave physics we recommend [3, 4].

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3.1 Shock wave generation

3.1 Shock wave generation

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Fig. 3-2: Principles of shock wave generators used in lithotripters (See text for description).

Left: Electro-Magnetic Shock wave Emitter (EMSE). Centre: Electrohydraulic shock wave emitter. Right: Piezoelectric shock wave emitter.

3.1.1 Electromagnetic The main component of an electromagnetic shock wave source is the ElectroMagnetic Shock wave Emitter (EMSE). The EMSE is driven by a high voltage electric pulse that causes a rapid movement of the EMSE’s membrane. This rapid forward movement of the membrane creates a planar acoustic pulse that is focused by an acoustic lens and transmitted to the patient through a water-filled bellow.

3.1.2 Electrohydraulic The main components of an electrohydraulic shock wave generator are the electrode, which is also referred to as spark plug, and an ellipsoidal reflector.

The underwater spark gap discharge between the tips of the electrode causes rapid local vaporization to occur in the water, which generates a high-amplitude pressure pulse. To focus the initial radial wave, the electrode is located at the focal point F1 of the ellipsoidal reflector. The shock wave is reflected by the walls of the ellipsoid creating a focused shock wave in the focal zone F2.

3.1.3 Piezoelectric Piezoelectric crystals expand rapidly when a high voltage electrical pulse is applied to them. In piezoelectric shock wave generators, a large number of piezoelectric crystals are synchronously excited, which creates a pressure wave. Focusing is accomplished by arranging the piezoelectric crystals in a spherical shape.

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3.2 Shock wave parameters Fig. 3-3 and Fig. 3-4 illustrate the pressure signal in the focus of a shock wave source. A shock wave is characterized by a very short rise time and short pulse duration followed by a negative pressure phase. A set of parameters is used to characterize a shock wave field.

3.2.1 Pressure P+ The maximum positive pressure is referred to as the positive peak pressure P+ and is measured in MPa. Typically the focal value varies between 30 and 120 MPa. The rise time ranges between 1 and 200 ns. The minimum negative pressure of the succeeding tensile phase is typically between -4 MPa and -15Â MPa.

Fig. 3-3: Shock wave pressure pulse as function of time measured in the shock wave focal zone F2.

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3.2 Shock wave parameters

3.2.2 Focus size The focus size is the Full Width at Half Maximum (FWHM) of the spatial pressure distribution, also referred to as the -6 dB focus (see Fig. 3-4). The FWHM is the width of the spatial pressure distribution at 50% of the peak pressure (maximum of the curve). It is related to the shock wave peak pressure and not to a threshold value, where disintegration becomes significant.

Therefore, disintegration is not limited to the focus size (Bohris et al. 2009).

3

The FWHM of different lithotripters varies between 2 mm and 20 mm. However, it should be noted that the focus size may also vary with the energy level in each lithotripter. Shock wave sources with larger focus size typically come with lower peak pressures than those with narrow focus.

Fig. 3-4: Curve illustrating the focus width (showing the -6 dB focus).

Initiated by Eisenmenger in 2001, there is still a controversial debate about the optimal focus size with regard to stone fragmentation with low side effects.

To date, the majority of researchers recommend large focus sizes. However, advantageous results with large focus devices were mainly obtained in lab tests and animal studies (Evan et al. 2008, Neisius et al. 2014). So far, clinical studies could not deliver significantly better results (Rassweiler et al. 2014, Bhojani et al. 2015).

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3.2.3 Penetration depth This is the distance between the coupling surface and the focal spot of the shock waves. The maximum penetration depth of lithotripters may vary.

3.2.4 Effective energy E12mm The effective energy E12mm is a measure of the energy per shock wave pulse in mJ that is transmitted through a circular area of 12 mm in diameter within the focus spot. (See Fig. 3-5).

Fig. 3-5: Effective Energy E12mm.

The blue circle represents the diameter of the cross section of a typical stone. The green arrow indicates the direction in which the shock wave travels. The total energy that passes through the circle is referred to as the effective energy.

3.2.5 Energy flux density The energy flux density ED is a measure of the energy concentration. It is measured in mJ/mm2, i.e. energy per unit area.

In focussed shock wave systems, the energy remains the same as the wave travels through a decreasing area on its way to the focal zone. Thus the energy flux density increases and reaches its maximum at the focus (See Fig. 3-6).

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3.3 Energy dose

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Fig. 3-6: Energy flux density.

The lower part of the illustration shows the lens (light red) of an EMSE system. The yellow cone indicates the shock wave path. Green circles indicate the area the shock wave passes through while travelling from the lens surface to the focal region. As the distance from the lens increases, the area traversed by the shock wave gets smaller. Conservation of energy dictates that the energy density must increase and reach its maximum at the focal point.

3.3 Energy dose With each shock wave pulse a certain amount of effective energy E12mm is applied. The energy dose then is the sum of applied effective energy for all shock wave pulses during the course of a stone treatment. It is synonymous with the accumulated energy.

Assuming that ramping is applied, the treatment starts at low energy level with Eeff1. After a given number of pulses n1, the energy is increased in steps, e.g. with n2 pulses of Eeff2, n3 pulses of Eeff3, a.s.o. Then energy dose is calculated as follows: Edose(12mm) = n1 Eeff1 + n2 Eeff2 + n3 Eeff3 + ‌ Within a certain acceptable range the same effect on treatment outcome and side effects can be expected provided that the applied energy dose is the same.

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3.4 Stone breaking mechanisms Stone-breaking mechanisms have been investigated since the early days of medical shock wave research. Four major effects that contribute to stone disintegration have been identified: • Hopkinson effect • Shear forces • Quasistatic squeezing • Cavitation Cavitation mainly contributes to the surface erosion of stones and fragments.

Its other effects contribute to the cracking that breaks the stone into pieces.

The Hopkinson effect, shear forces and quasistatic squeezing are caused by the differences in the speed of sound in tissue and in stones. Some basic information about the various stone-breaking mechanisms is provided in the following subsections.

3.4.1 Hopkinson effect The Hopkinson effect occurs because of a reflection of the shock wave at the rear surface of the stone. It causes the stone to break into large pieces. In analogy to light, acoustic waves are reflected and diffracted at the transition from one medium to another. When a shock wave is passing through a stone, it is partially reflected at the stone front and rear surfaces. However, at the rear surface of the stone, i.e. the transition from the more dense to the less dense medium, the reflected pulse component is associated with a reversal of the peak amplitude of the shock wave. Therefore, a high amplitude negative pressure wave travels in the direction opposite to that of the original wave, inducing high tensile forces in the stone. (See Fig. 3-7 for illustration).

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3.4 Stone breaking mechanisms

3 Fig. 3-7: Hopkinson effect.

The grey circle represents a stone. The incoming shock wave (1), travelling from left to right, is split at the front stone surface into a reflected (2) and transmitted (3) component. At the rear stone surface, the shock wave (3) is again partially reflected, resulting in a high-amplitude negative pressure wave (4).

3.4.2 Shear forces Shear forces are another effect caused by the different speeds of sound in stone and tissue. Inside the stone a shock wave travels faster than in surrounding tissue. A convergent wave is produced inside the stone, but outside the stone a divergent wave is created. This creates strong tensile forces in the stone, which contribute to crack formation within the stone.

3.4.3 Squeezing effect “Quasistatic squeezing� was postulated by Eisenmenger in 2001. Quasistatic squeezing is believed to occur as an effect of the faster speed of sound inside the stone versus that outside the stone. When the shock wave enters the stone it moves faster than the wave outside the stone. This would create circumferential compressive forces outside the stone and tensile stress inside the stone, which might contribute to stone fragmentation.

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3.4.4 Cavitation Every shock wave pulse has a trailing negative pressure phase. Its tensile forces create microbubbles in liquids like urine or blood. These cavitation bubbles are unstable and collapse with a rapid implosion (See Fig. 3-8).

The associated liquid jets cause a pitting of adjacent structures like stones.

Cavitation increases with shock wave frequency and intensity.

Fig. 3-8: Image sequence of a solid target exposed to a shock wave propagating from left to right. The second frame shows individual cavitation bubbles within the water and a bubble cluster on the face of the target. Whereas the single cavitation bubbles collapse quite early, the cluster grows further until it collapses, revealing an intermediate mushroom-like shape (680 μs).

3.5 Tissue effects Basically all effects that contribute to stone disintegration may also con­tribute to tissue damage.

Cavitation, which may occur for example inside blood vessels or in the urinefilled collecting system of the kidney, can cause vessel and parenchymal damage resulting in bleeding and haematomas. Recent literature shows that the risk of cavitation-induced renal damage increases with high shock wave frequencies and excessive intensities. When a shock wave passes through tissue it may strike cavitation bubbles created by a previous shock wave pulse.

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3.5 Tissue effects

This has two effects: • The shock wave energy is partly blocked by the cavitation bubbles so that the stone is exposed to reduced shock wave energy (See Fig. 3-9).

• The shock wave interfering with cavitation bubbles can create forced bubble collapse, which increases the risk of side effects.

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As a result, stone disintegration is impaired and the risk of side effects is increased. In a meta-analysis Semins, et al. (2008) found that patient treatments with 60 shocks per minute had a significantly better result than treatments with 120 shocks per minute. In a porcine model, it was found that shock rates of 60 per minute or lower could reduce kidney damage (McAteer et al. 2009).

Gas-filled organs, particularly the lung, are at high risk of severe tissue damage when exposed to shock waves. When shock waves reach the tissue/ gas interface, they are reflected, and the reflected shock wave is reversed in polarity (See also Hopkinson Effect). The resulting tensile forces at the interface can cause organ rupture (See Fig. 3-9).

Fig. 3-9: Left: Blocking effect of a cavitation bubble field. Cavitation bubbles within the shock wave path cause an attenuation of the shock wave. Compared to the undisturbed situation, the shock wave pressure amplitudes are lowered (See blue curves). Right: Reflection at a tissue/ air interface. The incoming shock wave (blue) is fully reflected. Due to the transition from the positive pulse into a negative pulse this region is exposed to strong tensile forces.

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4 Indications ESWL is a non-invasive treatment modality for stones in the entire urinary tract. With modern lithotripters all portions of the urinary tract are accessible.

Major advantages of ESWL over other procedures are: It is the least invasive treatment modality for urolithiasis. In the majority of cases it does not require anaesthesia. Generally, analgosedation is used for pain management. ESWL is very safe with a very low risk of side effects and serious complications.

The need for repeated ESWL sessions for adequate stone disintegration is frequently emphasised. Consequently, it is easy to get the impression that ESWL generally requires several treatments. This is a misconception.

Although repeated sessions are often necessary to achieve a good overall treatment result with SWL, a large fraction of patients can be adequately treated with only one session (Tiselius et al. 2008).

Despite ESWL’s potential as a universal method for stone treatment, selecting the right patients and stone locations is a prerequisite for success.

4.1 Renal stone treatment 4.1.1 General recommendation For patients with normal renal anatomy and stones located in the renal pelvis and the upper and middle calyx up to a size of 20 mm, shock wave lithotripsy is the preferred treatment modality. This is reflected in the current EAU guideline [5].

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4.2 Ureteral stonesRenal stone treatment

4.1.2 Special recommendation for lower pole stones The fragmentation efficacy of lower pole calyx stones is not different from stones in other calyces. However, numerous studies suggest that the discharge of stone debris is inferior from the lower calyx due to the unfavourable spatial anatomy of the lower pole collecting system.

In 1992, Sampaio et al. already reported that an acute lower pole infundibulopelvic angle, a narrow infundibular width, and a long infundibular length may predict a decreased stone-free rate. Although it is likely that the anatomy influences the stone clearance, it remains unclear which parameter has practical significance. Danuser et al. (2007) e.g. could not find any significant anatomical influence on the clearance of disintegrated stones from the lower calyx.

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Several studies have demonstrated that the most important factor influencing the treatment outcome is stone size. Therefore, ESWL should be the preferred treatment modality for lower pole renal stones up to a diameter of 10 mm.

Pearle et al. (2005) compared ESWL and ureteroscopic lithotripsy (URS) for treatment of small lower pole stones. In a randomized multicenter study they could not find a significant difference in stone-free rates. ESWL, however, was associated with greater patient acceptance and shorter convalescence.

For lower pole stones 11-20 mm in size ESWL outcome is inferior to endoscopic stone removal. However, ESWL might be an option because of its non-invasive nature and the low risk of complications.

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4 Indications

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4.2 Ureteral stones For the treatment of ureteral stones, SWL and URS are first line treatment options [6]. In Fig. 4-1, the stone-free rates after a single ESWL versus URS is shown for different stone sizes and locations. With both options, good results are obtained. URS achieves better stone-free rates, especially with larger stones and in lower ureteral stones. Only in small stones in the proximal ureter are the results with ESWL superior. The results with ESWL can be enhanced, if a second or third treatment is accepted. In a series of 598 ureteral stone patients treated with ESWL, Tiselius et al. (2008) achieved a stone-free rate of more than 97% with an average number of 1.3 treatment sessions. Of these patients, 76.3% required only one SWL session. It must be emphasised that for stones in the distal ureter, as many as 83.6% were satisfactorily treated with one session.

The advantages of ESWL compared with URS are the fact that it can be performed without general or regional anesthesia and the lower incidence of significant complications [6]. To some extent, this counterbalances the somewhat lower stone-free rate. Therefore, since there is less discomfort after treatment, ESWL is preferred by most patients, even if URS may remove the stone faster (Karlsen et al. 2007).

Fig. 4-1: Results of a meta-analysis presented in the AUA/EAU guideline [6]. It shows the stone-free rates of ESWL compared with URS for proximal, mid and lower ureteric stones after a single treatment. Left: Data for stones smaller than 10 mm. Right: Data for stones larger than 10 mm.

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4.4 Stone compositionSpecial indications

4.3 Special indications Special attention is needed in paediatric and obese patients as well as in patients with renal abnormalities.

4.3.1 Paediatric urolithiasis For paediatric patients ESWL is a safe and effective treatment method. In spite of its small diameter, the ureter has a high transport capacity for stone fragments, which explains why stone-free rates for children are superior to those in adults. There is no evidence that ESWL causes irreversible functional or morphological changes.

Therefore, ESWL remains the treatment of choice for stones in children (Lu et al. 2015). However, it is important to adapt the ESWL protocol to the smaller anatomical dimensions.

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The following recommendations may be helpful: • A paediatric positioning device should be used to assure safe patient positioning.

• Lungs have to be protected against shock wave exposure to avoid tissue damage.

• Radiation exposure should be minimized; if possible, ultrasound localization should be used.

• Shock wave energy should be as low as possible.

See section 6.8 for details.

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4 Indications

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4.3.2 Obesity Overall, ESWL is challenging in morbidly obese patients due to difficulties with stone visualization and positioning. The coincidence of obesity with large and hard stones is likely to result in poor stone clearance. However, in experienced hands, ESWL is a reasonable therapy option for obese patients with stones < 20 mm. Shock wave devices having a deeper penetration depth can also be expected to improve outcomes.

Pareek et al. (2005) found that a skin-to-stone-distance exceeding 10 cm was associated with ESWL treatment failure. In contrast, Muùoz et al. (2003) reported a 3-months stone-free rate of 72% and concluded that lithotripter properties and operator experience were the secret of success. Similar results were found by Mezentsev et al. (2005). In morbidly obese patients (BMI > 40 kg/m²) an overall 3-months stone-free rate after ESWL of 73% was achieved.

In obese patients the main problem is the proper targeting and focussing of the stones. Therefore lithotripters with high resolution imaging systems, versatile coupling of the therapy head above and under table, and a sufficient SW penetration depth are expected to yield better results.

Experienced operators also use simple positioning tricks to improve targeting in obese patients.

4.3.3 Renal anomalies Renal anomalies are often associated with an impaired drainage and consequently a reduced clearance of stone fragments. In their review Sheir et al. (2003) reported a 72.2% stone-free rate after 3 months in patients with anomalous kidneys. Turna et al. (2007) concluded from a retrospective analysis of management of calyceal diverticular stones that ESWL is suitable to render most patients symptom-free with minimal complications despite a low stonefree rate of 21%.

For patients with renal anomalies the treatment procedure should be chosen individually considering kidney function and location, stone size, availability of appropriate equipment and expertise of the performing urologist and even accepting multiple treatments.

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4.4 Stone composition

4.4 Stone composition It is known that stone composition and internal stone structure are important characteristics that determine the hardness of urinary calculi and therefore the responsiveness to shock waves. There have been numerous attempts to use non-contrast computed tomography (NCCT) to predict ESWL success rate based on Hounsfield unit (HU) measurements. There is no consensus, though, as to which HU values will predict ESWL success or failure.

Even hard concretions like brushite and cystine stones are not a contraindication for ESWL if the stone burden is small and the patient prefers a non-invasive therapy.

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5 Contraindications The following conditions are absolute contraindications, and patients who have them should be considered for alternative treatment modalities: - Pregnancy - Untreated coagulation abnormalities - Continued use of anticoagulants prior to ESWL - Pulmonary tissue in the shock wave path - Tumour in the shock wave path - Aneurysms in the shock wave path - Pathological changes in the shock wave path - Active pyelonephritis Pregnancy remains an absolute contraindication due to the possible use of fluoroscopy but above all due to the possible adverse effects of the shock wave on the foetus.

Given that untreated coagulation abnormalities dramatically increase the risk of large perirenal and subcapsular haematomas, they are an absolute contraindication for ESWL. The influence of medications containing acetylsalicylic acid is under discussion. Most of the available publications recommend a break of four to seven days.

Untreated hypertension is considered a relative contraindication and should be regulated before treatment.

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6 How to perform ESWL? This section provides general practical guidelines for ESWL. The order of the various activities – device preparation, pain therapy, patient preparation, positioning, stone targeting, coupling and shock wave application – is based on the workflow of the ESWL treatment. This will facilitate implementation of the clinical process. All of these activities contribute in one way or another to good stone disintegration combined with low tissue injury and patient safety. This chapter is the result of long lasting experience of the authors and others [7-10]. Most points are also applicable when treating children.

However, special aspects of paediatric ESWL are summarized in section 6.8.

6.1 Device preparation When treating a patient, it is important to be sure that the lithotripter is in proper working order. The alignment of the imaging systems (X-ray and ultrasound) is especially critical and must be checked daily after the system is initially started. The target mark superimposed on the image must not deviate from the actual lithotripter focus. This would cause incorrect stone alignment and thus reduced disintegration and possible tissue injury. Manufacturers provide special test equipment and phantoms for these tests (See lithotripter user manual). The images obtained with the tests should be stored or printed out in order to document correct alignment.

The coupling cushion and patient table must be clean in order to avoid crosscontaminations between patients.

The lithotripter coupling cushion needs to be checked for possible air bubble inclusions. Any air that is present needs to be evacuated as described in the user manual.

• Check the status of the lithotripter.

• Check the alignment of the ultrasound and X-ray imaging systems.

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6.2 Pain management

6.2 Pain management ESWL is a potentially painful procedure and sufficient analgesia is mandatory for good treatment results. Pain arising during ESWL is a multifactorial event.

On the one hand cutaneous superficial skin nociceptors are stimulated, on the other hand visceral nociceptors in the renal capsule, periosteum, pleura, peritoneum and muscles are involved.

Patients who experience pain tend to move voluntarily or involuntarily and show increased respiratory motion. Consequently, the target moves out of the shock wave focus and the hit rate decreases. This correlates with impaired stone fragmentation and a subsequent impaired stone clearance. Additionally, pain can prevent the planned shock wave dose from being applied, i.e. the shock wave energy level and the number of pulses. It may also cause a rise in blood pressure, which may lead to more complications like a higher rate of kidney haematomas.

The pain is highly dependent on the shock wave energy level applied. It is also increased if the skin is close to the shock wave focus, as is the case in thin patients. There are also patient-related factors like age, gender and body habitus. In particular, young female patients and anxious or depressed patients experience more pain during ESWL.

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In routine clinical practice, there is a rather broad spectrum of protocols for pain treatment in ESWL. They may range between the extremes of general anaesthesia and simple oral medication.

General anaesthesia for ESWL treatment is an option. General anaesthesia is safe and morbidity is low, with the obvious exception of high-risk patients.

It is associated with a higher overall cost and a longer overall procedure time due to the need for post-operative recovery. It may entail practical problems, in particular with outpatient procedures. However, in young children or in extremely anxious patients, general anaesthesia is the method of choice.

Intravenous analgosedation is possibly the most widely used protocol for ESWL treatment. It is suitable for most patients and overall costs are significantly lower than general anaesthesia. The administration of alfentanil with or without propofol, which can be intermittently repeated when necessary, has a long history of effective use.

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For adaptive dosage during the treatment, the use of a patient-controlled medication pump is a well-proven option. ECG, blood pressure and oxygen monitoring are obligatory when administering opioids. Possible side effects are nausea, vomiting and respiratory depression.

• Effective pain management is mandatory for good treatment results.

• The need for pain treatment depends on shock wave energy level, skin-to-stone distance and patient-related factors.

• Intravenous analgosedation, which can be intermittently repeated when necessary, is the most common therapy to manage ESWL-induced pain.

6.3 Patient preparation Any necessary monitoring sensors, such as ECG electrodes, should be attached to the patient before stone targeting in order to avoid delays once the stone has been located and positioned in the shock wave focus. Likewise, the monitors which are required for the specific protocol and patient-related risks should be started. RR blood pressure should be monitored, since increasing blood pressure (RR > 160/95 mm Hg) caused by pain, stress or insufficient control of pre-existing hypertension may increase the risk of inducing kidney haematomas.

The complete urinary tract needs to be examined immediately prior to ESWL in order to confirm the actual position of the stone and compare the findings with pre-treatment diagnosis. The concretion may have changed its position, which may require an updated treatment strategy.

Briefly but fully explaining the treatment procedure to the patient can significantly improve the patient’s relaxation and cooperation.

• Start the monitoring instruments (ECG, O2 saturation, RR).

• Urinary tract examination immediately before ESWL. • Confirm the position of the stone.

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6.4 Positioning

6.4 Positioning Patient movements during shock wave application and respiration cause the stone to move out of the shock wave focus and are detrimental to stone disintegration. Therefore, a stable patient position is essential for good disinte­ gration results. Since the treatment typically takes about 30 to 45 minutes, the patient requires a comfortable position. A neck roll, knee roll, a wedge or arm rests are accessories that help to stabilize the patientâ&#x20AC;&#x2122;s position. If possible, the supine patient position is preferred, since it is more comfortable for the patient and offers better access to the patient for the anaesthetist when doing general anaesthesia.

With a lithotripter offering both under-table and over-table therapy head positions, the patient can be treated in a supine position for all stone locations (See Fig. 6-1). Stones in the kidney and upper ureter down to the iliac crest are treated with the therapy head coupled in the dorsal or dorsolateral location.

Since the iliac crest blocks the shock waves, stones in the distal ureter require a ventral or ventrolateral therapy head position. If the lithotripter only permits under-table therapy head positions, the patient needs to be positioned prone for ureteral stones distal to the iliac crest.

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Fig. 6-1: Dornier Gemini lithotripter. Left: Set-up for stone treatment in left kidney. The therapy head (indicated by an arrow) is coupled from dorsolateral. Right: Setup for stone treatment in right lower ureter. The therapy head is coupled from the ventrolateral position.

It is advisable to pre-position the patient in such a way that the stone is already in close proximity to the focus. This will avoid time-consuming moves later in the procedure.

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Abdominal compression by a belt reduces respiration-induced stone move­ ments and thus increases the efficacy of the ESWL treatment. The belt should press on the abdomen and not on the thorax.

• A stable patient position is essential.

• Stones in the kidney and proximal ureter down to the iliac crest – therapy head dorsal.

• Stones in the distal ureter – therapy head ventral.

• Abdominal compression suppresses respiratory motion.

6.5 Stone targeting Most modern lithotripters offer both X-ray and B-mode ultrasound for stone visualization (See Fig. 6-2).

Fig. 6-2: Left: Native X-ray image with radiopaque stone within the crosshairs. The lithotripter coupling cushion of the therapy head is shading the right side. Right: Ultrasound image of a kidney stone. Within the crosshairs it is displayed by its bright stone reflection. It is accompanied by an “acoustic shadow” behind the reflection.

Calcium oxalate and calcium phosphate stones are radiopaque and have a high density. Struvite, mixed and cystine stones have a lower density but are still visible on native X-ray images. Uric acid stones are radio-translucent and can only indirectly be visualized by X-ray using a contrast agent.

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6.5 Stone targeting

With ultrasound stones are visualized by a bright echo marking the stone surface regardless of the stone’s chemical composition. The characteristic “acoustic shadow” behind the bright stone reflection distinguishes a stone from other bright structures such as blood vessels or a stent. Ultrasound is unsuitable for visualization of ureteral stones unless they are very proximal in a dilated system or pre-vesical where the bladder serves as an “acoustic window”. In the middle section of the ureter, ultrasound scanning cannot be used to locate stones, since anatomical landmarks are missing and intestinal gas and bone interfere (See Fig. 6-3).

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Fig. 6-3: Ultrasound imaging is appropriate for kidney stones, proximal and distal ureteral stones.

6.5.1 X-ray guided ESWL X-ray is the first-line modality for imaging in ESWL, especially in the United States. In order to target the stone in three dimensions, the stone has to be aligned in two different X-ray projection planes. If the patient is in supine position, the stone is typically localized in the coronal plane by the vertical C-arm position (PA projection). The stone is adjusted in the craniocaudal (X-axis) and laterolateral axis (Y-axis). In the angled C-arm position (CC projection), the stone is adjusted along the frontal axis (Z-axis). The targeting of the stone is supported by software functions specific to the lithotripter model (e.g. image-oriented movement, auto-positioning).

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Initially, the full image area is used to confirm the position of the stone taking into account visible landmarks like the spine and ribs. Once the stone has been identified and is located in the shockwave focus, the imaged region of interest has to be reduced in size by closing the X-ray collimator. This effectively reduces the patient’s radiation exposure.

Since the target may get out of the shock wave focus due to patient movement or stone movement within the patient, stone positioning must be reconfirmed at regular intervals. If there is an apparent patient movement, stone targeting must be checked immediately after the patient has returned to a stable position. Otherwise imaging may be repeated, for example: every 300-500 shock waves. Even though stone movements are more likely within the coronal plane, imaging should not rely solely on the vertical C-arm position.

Especially in the beginning of the treatment and if the position was corrected in the coronal plane, the ventrodorsal axis should be checked with the angled C-arm position.

During ESWL treatment, the degree of stone disintegration may be assessed by direct signs (cracks in the stone, visualisation of multiple fragments) or indirect signs (loss of density, “softening” of the margins).

• Target the stone in both image projection planes (PA and CC).

• Stone targeting must be reconfirmed at regular intervals.

• Reduce the image size for monitoring (reduction of radiation exposure).

6.5.2 Ultrasound guided ESWL Even though most urologists routinely use ultrasound imaging for examinations of the urinary tract and for stone diagnosis, ultrasound guided ESWL is considered more difficult. This may be explained by the fact that the transducer is typically located either within the bulky therapy head or fixed in a holder. Thus, the scanning of the patient is quite different from the normal procedure in ultrasound examinations where the ultrasound scanner can be moved freely over the target organ. Instead of making small manual angular movements, the operator now has to move the patient by means of table movements.

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6.5 Stone targeting

Therefore, it can sometimes prove more difficult to find a good acoustic window in intercostal spaces. Consequently, image quality is often inferior to standard freehand scanning. With inline ultrasound, image quality may suffer from additional artefacts caused by the coupling cushion and air bubbles in the coupling interface.

However, ultrasound guided ESWL is a procedure which can be learnt with some training and is not more demanding than other standard procedures performed by urologists. The use of ultrasound has some relevant advantages over X-ray guidance: - There is no radiation exposure to the patient or personnel. Therefore, ultrasound can be used in continuous mode (â&#x20AC;&#x153;real timeâ&#x20AC;?) during the complete session.

- Real-time imaging allows better monitoring of the entire procedure: movements of the targeted stone or the patient are detected immediately.

- Smaller renal stones might be easier to detect.

- Uric acid stones can be visualized without the use of a contrast agent.

- During shock wave application a stone which is hit by shock waves seems to slightly jump, which is also sometimes described as pixel flickering. This may be used to monitor hits/misses.

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- With inline ultrasound it is also possible to check the acoustic path of the shock waves, especially the coupling quality (See Fig. 6-4 and section 6.6).

Given these advantages, we recommend that ultrasound be used whenever possible.

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Fig. 6-4: Ultrasound monitoring of the contact zone with an inline transducer.

Left: A bubble is revealed by its bright echo (white arrow) and posterior shadow (black arrows).

Right: Image after removal of the bubble by wiping the cushion.

Achieving prompt and reliable stone localization by ultrasound is highly dependent on the actual lithotripter being used. However, we like to stress that there are possible advantages to initial scanning with a freehand transducer.

In this way it is possible to confirm that the stone planned for treatment can be adequately visualized by ultrasound. Also the suitable acoustic window which could be used later with the outline or inline transducer may be selected. A pre-positioning of the patient such that only minor corrections are needed in the succeeding targeting is advisable.

• Use ultrasound imaging whenever possible.

• Pre-scanning with freehand ultrasound (-> selection of acoustic window for imaging, pre-positioning of the patient).

• Check for posterior stone shadow.

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6.6 Coupling

6.6 Coupling With most modern lithotripters, the shock waves are transmitted from the shock wave source to the patient via a water-filled cushion. To achieve a good transmission into the body, typically ultrasound gel is applied.

Various studies have shown that even a few air bubbles trapped in the gel considerably reduce the efficacy of the shock waves (See Fig. 6-5). In particular, incomplete coupling or a cushion which does not fit snugly against the body surface but has an air-filled wrinkle inevitably leads to ineffective treatment.

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Fig. 6-5: Reduction of disintegration capability by air trapped within the coupling zone. Results from in vitro model stone tests (for details see Bohris et al. 2012). Test results are the number of shock waves required for complete disintegration of the stone. Test was performed under various coupling conditions. When 20% of the coupling area was blocked by air bubbles, about three times the number of shock waves was needed as compared to the bubble-free condition.

Some tips help to obtain a bubble-free coupling and avoid poor coupling conditions (See table).

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• Remove hair at the shock wave entry area.

• Store the gel bottle head down and do not shake it before use.

A large opening instead of a small diameter nozzle should be used when dispensing gel.

• Apply a sufficient amount (30–50 ml) of low viscous ultrasound gel on the therapy head as a mound (See Fig. 6-6).

• Contact between the cushion and the patient should be achieved by inflating the bellow or slowly lowering the patient onto the inflated bellow. Typically the gel spreads radially without air entrapment.

• Once good coupling is attained, the contact between cushion and patient must not be lost during treatment. If contact is lost, the coupling procedure needs to be restarted.

• Coupling can be improved by manually wiping the cushion (See Fig. 6-6). Wiping is recommended after decoupling or frequent patient repositioning steps.

• If available, employ inline ultrasound or surveillance video to monitor coupling.

Fig. 6-6: Left: Applying gel to the cushion. Right: Improving coupling by manually wiping the cushion. During this procedure the inflation pressure and patient position should be maintained so that the contact between bellows and skin is not lost.

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6.6 Coupling

If a surveillance camera is integrated into the therapy head (Fig. 6-7), the coupling zone can be visualised at a glance. Monitoring and removal of air bubbles becomes very convenient with this feature (Fig. 6-8). Inline ultrasound may be used for the same purpose (see Fig. 6-4). However, the ultrasound image contains only an intersecting line, meaning a 180° scan of the coupling area is required.

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Fig. 6-7: Dornier OptiCouple. Illustration of the position of the video camera within the therapy head for monitoring the coupling area between patient and coupling cushion.

Fig. 6-8: Video monitoring of the coupling area. Left: Numerous bubbles (dark) are located within the gel layer (bright). Right: Area after removal of the disturbances by wiping the cushion.

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A clinical study including 198 treatments proved that a video camera incorporated into the therapy head of a Dornier Gemini lithotripter could consistently achieve bubble-free coupling. Compared with treatments performed without video control, the same results were obtained with fewer SW numbers at a lower energy level [11]. In kidney stones, the average energy dose (c.f. section 3.3) per treatment could be lowered by about 43%.

6.7 Shock wave application – treatment parameters The aim of ESWL is to disintegrate a stone into fragments that can pass through the urinary tract system spontaneously. The disintegration improves as the shock wave energy dose, which is the total shock wave energy applied during one treatment, increases (See section 3.3). The energy dose must be sufficient to achieve adequate stone fragmentation and clearance so that the need for further procedures (re-ESWL, URS, PNL) is reduced. On the other hand, overtreatment must be avoided since the risk of side effects is also directly related to energy dose.

6.7.1 Kidney stones Within a certain range the accumulated shock wave dose may be applied using different energy settings. If a lower energy is chosen, though, this must be compensated by applying a larger number of shock waves. It is generally recommended to adjust the total dose and energy level to the individual patient (obesity, risk factors) and stone characteristics (stone size, chemical composition). Patient risk factors that require a lower shock wave dose are: • Untreated hypertension • Diabetes mellitus • Age > 65 years • Impaired renal function, hydronephrosis • Paediatric patients Renal tissue damage and resulting haematoma can be caused by cavitation (See section 3.4.4). The tensile stress of the shock wave may induce small vapour bubbles in the blood. These bubbles are not stable but collapse after a sub-second lifetime. Both bubble expansion and collapse are accompanied by forceful stress to the proximity of the bubble which can damage the capillary walls.

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6.8 Shock wave application – treatment parameters

The risk of inducing cavitation within the renal parenchyma increases with the energy level used. Various recent publications have indicated that the occurrence of cavitation is strongly related to the pulse repetition frequency.

Lowering the pulse repetition frequency (PRF) is thus an effective way to avoid renal vascular damage. In addition, a slower PRF will also improve stone disintegration, since a blocking effect by cavitation is avoided (See section 3.5).

A pre-treatment (100-500 shock waves) at low energy levels is recommended to activate a protective effect in the kidney. Animal studies have shown that shock waves reduce the glomerular filtration rate and the renal plasma flow in the area exposed to the shock waves and even in the contralateral kidney due to induced vasoconstriction.

If ESWL is performed with intravenous analgesia, it is a common practice in any event to increase the energy stepwise in order to adapt the patient to the shock waves. Operators who apply ESWL under full anaesthesia and start immediately with high-power shock wave levels should switch their strategy to a gradual energy increase in order to achieve better results.

6.7.2 Ureteral stones

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If the stone is located in the ureter instead of the kidney, the dose required for complete stone disintegration is generally higher. On the other hand, a somewhat higher energy level and shock wave frequency may be used if the kidney is not within the shock wave path. If the kidney is within the shock wave path, the same shock wave parameters as for kidney stones should be employed. This is of importance when treating upper ureteral stones.

• Adjust the shock wave parameters to the individual case.

• A low shock wave repetition frequency provides less renal vascular damage and better stone fragmentation. Use 60 shocks per minute.

• Activate vasoconstriction by a pre-treatment of low energy shocks combined with ramping up the energy slowly.

• When treating upper ureteral stones, check if the kidney is within the shock wave path. Adjust shock wave parameters accordingly.

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6.8 Paediatric urolithiasis This section addresses some aspects specific to ESWL in the paediatric population [12]. Especially in this group the shock wave energy dose and radiation dose must be adapted to avoid the risk of long-term adverse effects, especially if patients need to undergo repeated ESWL. Also the smaller anatomy requires some adaptations in the procedure and settings.

6.8.1 Anesthesia Whereas ESWL can be administered without general anaesthesia to most adults, this is different with children. The need differs considerably depending on the age of the child and the shock wave energy applied. Older children often tolerate ESWL under intravenous sedation, but with younger children general anaesthesia is the first choice.

6.8.2 Paediatric positioning aid The table cut-out may be too wide for the treatment of infants. Some manu­ facturers provide special positioning aids like an acoustically transparent sheet that supports the body as shown in Fig. 6-8. Bubblefree acoustic coupling must be provided between the coupling cushion and the sheet and between the sheet and the body.

Fig. 6-9: Positioning aid which supports the body at a table cut-out.

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6.8 Paediatric urolithiasis

6.8.3 Lung protection Because the lungs in children are in closer proximity to the kidneys, special care needs to be taken to protect lung parenchyma from the shock waves, particularly when treating upper pole stones. The lung needs to be shielded with shock wave-absorbing materials, such as sheets of polystyrene or foam.

6.8.4 Imaging Image quality in children is generally better due to the smaller penetration depth. To avoid radiation exposure, ultrasound is the preferred imaging modality. It also permits continuous and close monitoring (real-time imaging).

6.8.5 Adapted shock wave parameters The necessary energy dose as defined by shock wave energy level and number of shocks is generally lower in children than in adults. This may be attributed to the smaller skin-to-stone distance and the good ability of the paediatric ureters to pass stones. However, an adequate dose must be selected by balancing safe stone clearance with avoiding auxilliary procedures which are related with potential additional risks.

• Paediatric positioning aid.

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• Lung protection for children (e.g. polystyrene between the chest and coupling bellow).

• Minimizing radiation exposure: preferably ultrasound localization.

• Adapt shock wave parameters.

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7 Follow-up

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7 Follow-up Stone clearance is monitored in follow-up examinations. Success is verified, or auxiliary procedures are specified. Even though severe complications induced by ESWL are rare, subcapsular haematomas or septicaemia can lead to life-threatening conditions. Such complications must be identified and properly treated.

7.1 Stone clearance After stone disintegration by ESWL, episodes of ureteral colic during passage of fragments are common (8-10%). Renal colic should be dealt with lege artis. In case of (rapid onset) massive pain, an ultrasound exam is indicated to rule out renal haematoma (See section 7.3.1).

In the treatment of kidney stones, colicky pain may be reduced and obstruction may be avoided by stenting. The insertion of a stent prior to ESWL is advised when the largest stone diameter exceeds 20 mm. However, routine stenting, especially in the case of ureteral stones, is not recommended [5].

Pharmacological facilitation of fragment passage or medical expulsion therapy (MET) can be accomplished by administering Îą-receptor antagonists.

Tamsulosin is the commonly used compound, but other Îą-blocking agents appear to be similarly effective. MET is not recommended for the paediatric population due to the limited data for that group.

Mechanical percussion and inversion therapy may enhance passage of fragments, especially originating from the lower pole calyces.

In most cases, a plain X-ray (KUB) is taken to define the status of stone clearance.

Stone-free rates are typically high in ureteral stones, even though repeated ESWL treatment sessions are occasionally required.

In kidney stones, however, a substantial number of patients show residual fragments. Residual fragments that originate from struvite, brushite and cysteine stones need to be cleared as far as possible because of the high recurrence risk of these stones (Tiselius 2009). The need for immediate fragment clearance of calcium stones (COM, COD and calcium phosphate crystals other than brushite) is a matter of debate. It is doubtful that extensive surgery for this purpose is beneficial for the patients.

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7.2 Stone analysis â&#x20AC;&#x201C; prevention of new stone formation

When those fragments are small and are without symptoms, they are referred to as clinically insignificant residual fragments (CIRF) or asymptomatic residual fragments (ARF). The number of patients who are stone-free typically increases with time.

Therefore, most clinical reports do not report stone-free rates until after 3Â months. Final evacuation of CIRF or ARF from the lower pole calyx may take up to 24 months. However, it must be noted that the management of patients with residuals after ESWL is an area that is still broadly debated.

7.2 Stone analysis â&#x20AC;&#x201C; prevention of new stone formation Measures to prevent new stone formation or to avoid growth of rest fragments are mainly dependent of stone composition.

In order to provide the patients with advice regarding preventive measures to avoid new stone episodes, it is therefore advisable to obtain a stone analysis on the evacuated fragments if and whenever possible.

The full extent of medical therapy of different stone types is a vast chapter and is beyond the scope of this booklet on the good practice of ESWL. We refer to the literature [13, 14].

7.3 Complications Generally and especially in comparison with endoscopic techniques complication rate following ESWL is extremely low.

Severe complications are extremely rare. Appropriate precautions need to be taken to avoid them.

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7.3.1 Renal haematoma In the literature the incidence of an asymptomatic haematoma is reported to vary between 4% and 19%. However, the incidence of a symptomatic haematoma is less than 1% [5]. Abnormal pain following ESWL is an alarm symptom and should trigger further detailed examinations. Further clinical signs are bulging and/or tenderness of the flank region, tachycardia, hypotension or signs of acute anaemia. The majority of manifested haematomas can be treated with a conservative approach, including blood transfusion in rare cases. Resorption may take 6 weeks to 6 months.

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7 Follow-up

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Although the risk of an induced haematoma cannot completely be eliminated, it can be minimized when the ESWL is competently performed and the patientâ&#x20AC;&#x2122;s risk factors are identified and addressed.

Adequate ESWL treatment was described in detail in Chapter 6 of this booklet. In short, blood pressure monitoring (See section 6.3), precise shock wave targeting (See section 6.5) and careful selection of the treatment parameters (See section 6.7) are essential. In addition, it is recommended that ESWL treatments not be repeated within overly short intervals. There is no consensus as to the minimum interval, and this interval may also depend on the acoustic doses administered. However, we suggest waiting at least one week before performing a re-ESWL. Patient related risk-factors are: - Treatment with anticoagulants (acetyl salicylic acid, coumarins, warfarin, etc.)

- Coagulation disorders - Hypertension or history of hypertension - Diabetes mellitus - High age (> 65-70) Patients who take anticoagulants like aspirin, warfarin or similar agents should not be treated unless the medication is temporarily discontinued or substituted. For details, it is referred to Alsaikhan et al. (2011).

ESWL should not be performed on patients with coagulation disorders or hypertension unless they have been medicinally corrected.

In all patients with risk factors the ESWL treatment parameters should be adapted to the specific case.

7.3.2 Septicaemia In order to anticipate eventual infectious problems it is wise to perform a urine culture prior to ESWL in all patients, especially those with larger stones.

Any urinary tract infection diagnosed prior to ESWL should be adequately treated with antibiotics before scheduling the treatment. In the case of large, potentially infected stones, antibiotic coverage should continue during and after ESWL.

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7.4 Long-term complications

In cases of urosepsis the highest priority must immediately be given to removing any obstruction caused by a stone or a fragment that might be present. Further medical treatment of the septic problems cannot be successful until a possible obstruction has been removed.

7.4 Long-term complications An initial study by Krambeck et al. (2006) identified a higher risk of developing hypertension or diabetes mellitus in patients treated by ESWL. Thereupon, several studies with large patient numbers were published.

Reviews and meta-analyses by Yu et al. (2014) and Deng et al. (2015) investigate a possible link between ESWL and hypertension and diabetes mellitus, respectively. However, no association between ESWL and the long-life risk of developing hypertension or diabetes mellitus could be identified.

It is now suggested that urolithiasis per se and the metabolic disorders associated with it may be responsible for changes in blood pressure and the higher incidence of diabetes mellitus regardless of any stone treatment modality.

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8 Summary

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8 Summary ESWL is still the least invasive of all treatment modalities and remains an excellent first-line treatment for the majority of patients with urolithiasis at all levels of the urinary tract.

Patients also prefer ESWL over endoscopic procedures. With ureteroscopy they may become stone-free faster, but most patients still prefer ESWL because there is less discomfort after treatment (Karlsen et al. 2007). The postoperative pain after ureteroscopy appears to be responsible for the fact that the patientâ&#x20AC;&#x2122;s quality of life is better after an ESWL when compared with ureteroscopy (Hamamoto et al. 2015).

Although in some regions reimbursement obviously is in favour of URS, ESWL still remains the more economically-favourable method. To favour a more invasive treatment option over ESWL for economic reasons appears to be a patient-unfriendly step backwards (Tiselius 2005).

In recent years the importance of operator expertise in obtaining optimal results with ESWL was highly underestimated. In endourology there is usually extensive training and tutoring, while in ESWL this is mostly neglected, leading to a lack of expertise and poorer results. Training can improve results, i.e. stone free-rates and a decrease in necessary retreatments (Okada et al.

2013). We strongly believe that with a more comprehensive understanding of the basic principles of ESWL much better results could be achieved in the future, leading to a renaissance of ESWL as first-line therapy for urolithiasis.

Last but not least: parallel to the rapid progression in endourological techniques with the development of smaller scopes and better disposables, there is also continuous technical progress in lithotripter technology [15].

This booklet focuses on the basic principles and practical aspects of ESWL and is intended to serve as an aid to all urologists and residents performing ESWL. The literature section lists various review articles that are recommended for further reading.

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9 Literature

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9 Literature [1] C. Chaussy, W. Brendel et al. Extracorporeally induced destruction of kidney stones by shockwaves. Lancet 316:1265-8, 1980.

[2] G.G. Tailly. Lithotripsy Systems. In A.D. Smith, G.H. Badlani et al. (Eds.) Smith’s textbook of Endourology (3rd Edition). WileyBlackwell, 2012, pp 559-75.

[3] A.M. Loske. Shock wave physics for urologists. Mexico: Universidad Nacional Autónoma de México. ISBN: 978-970-32-4377-8.

[4] R.O. Cleveland, J.A. McAteer. Physics of shock-wave lithotripsy.

In A.D. Smith, G.H. Badlani et al. (Eds.) Smith’s textbook of Endourology (3rd Edition). Wiley-Blackwell, 2012, pp 529-58.

[5] C. Türk, T. Knoll et al. Guidelines on Urolithiasis. European Association of Urology, 2015.

[6] G.M. Preminger, H.G. Tiselius et al. EAU/AUA Nephrolithiasis Guideline Panel. 2007 guideline for the management of ureteral calculi. J Urol 178:2418-34, 2007. (reviewed and validity conformed in 2010) [7] H.-G. Tiselius, C.G. Chaussy. Aspects on how extracorporeal shockwave lithotripsy should be carried out in order to be maximally effective. Urol Res 40:433-46, 2012.

[8] J.J. Rassweiler, H.-M. Fritsche et al. Extracorporeal shock wave lithotripsy in the year 2012. In T. Knoll, M.S. Pearle. Clinical Management of Urolithiasis. Springer, 2013, pp 51-76.

[9] C. Bach, N. Buchholz. Shock wave lithotripsy for renal and ureteric stones. Eur Urol Suppl. 10:423-32, 2011.

[10] M.J. Semins, B.R. Matlaga. How to improve results with extra­ corporeal shock wave lithotripsy. Ther Adv Urol 1:99-105, 2009.

[11] G.G. Tailly, M. M. Tailly-Cusse. Optical coupling control: an im­por­ tant step towards better ESWL. J Endoruol 28:1368-73, 2014.

[12] A. D’Addessi, L. Bongiovanni et al. Extracorporeal shockwave lithotripsy in pediatrics. J Endourol 22:1-22, 2008.

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9 Literature

[13] M.S. Pearle, D.S. Goldfarb et el. Medical managment of kidney stones: AUA guideline. J Urol 192:316-24, 2014.

[14] A. Hesse, H.G. Tiselius et al. Urinary stones. Diagnosis, treatment and prevention of recurrence. 3rd Edition. Karger, 2009.

[15] C.G. Chaussy, H.-G. Tiselius. Engineering better lithotripters.

Curr Urol Rep 16:52, 2015.

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Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book.

Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers´ leaflets accompanying each drug or system and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Every dosage schedule or every form of application used is entirely at the userâ&#x20AC;&#x2122;s own risk and responsibility.

The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed.

9

Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

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HM1 at the Munich University Hospital GroĂ&#x;hadern

The first extracorporeal shockwave lithotripsy (ESWL) treatment of a human was performed on February 07, 1980 by Christian Chaussy, Dieter Jocham, and Bernd Forssmann using a prototype Dornier HM1 (Dornier Human Model 1). The results with this new treatment modality were so successful, that it thoroughly revolutionized modern stone management.

The purpose of this brochure is to inform the user about the physical principles behind the technology and to offer practical guidance on performing ESWL.

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