10th Campbell reading:

STONE REMOVAL: SURGICAL TECHNIQUE AND TECHNOLOGY

INTRACORPOREAL LITHOTRIPTERS

Akmal Fawzi

Intracorporeal Lithotripsy Techniques Four techniques are available for intracorporeal lithotripsy:

Flexible Lithotripters: Electrohydraulic lithotripsy (EHL) Laser lithotripsy

Rigid Lithotripters: Ultrasonic lithotripsy Ballistic lithotripsy

Flexible Lithotripters

Electrohydraulic Lithotripters EHL was invented in 1955 by Yutkin, an engineer at the University of Kiev The first reported use of EHL outside the Eastern bloc was in 1960, when a modified version of Yutkins invention, the Urat-1, was used to fragment bladder calculi (Rouvalis, 1970)

The EHL probe is essentially an underwater spark plug composed of two concentric electrodes of different voltage polarities separated by insulation

Unlike in SWL the shockwave is not focused, so the stone must be placed where the shockwave is generated.

Electrohydraulic Lithotripters The improvements in technology allowed the development of smaller probes, from 9

fr become 1.6 to 5 Fr, that were safer and had the ability to be passed through small diameter, flexible ureteroscopes without occluding the irrigation or working channel.

Subsequent improvements in the EHL generator allowed the surgeon more control over energy discharge, pulse, and duration.

Denstedt and Clayman (1990) demonstrated that EHL works equally well in a normal saline solution, eliminating the hazard of irrigating the upper urinary tract with a hypotonic solution.

Electrohydraulic Lithotripters Advantages:

EHL will successfully fragment 90% of stones.

Probe flexibility, especially the smaller probes such as the 1.9 Fr.

The least costly intracorporeal device

Electrohydraulic Lithotripters Disadvantages:

Ureteral Perforation (the risk of perforation is greater with higher energies, such as in treatment of a hard stone)

Retrograde propulsion of calculi and fragments can occur during EHL and is more pro- nounced than with holmium:YAG lithotripsy

Another disadventage of EHL compared with holmium:YAG lithotripsy is the larger number and size of fragments produced, especially for stones larger than 15 mm

Electrohydraulic Lithotripters Technique:

Used the smaller 1.6- and 1.9-Fr probes

The EHL fiber tip should be positioned 2 to 5 mm distal to the end of the ureteroscope

The probe is placed about 1 mm from the stone surface

The goal of the treatment is to create fragments that can be removed with grasping forceps or a basket device or fragments that are likely to pass spontaneously.

After 50 to 60 seconds of firing, the insulation at the tip of the probe may peel away and at this time a new probe should be used

Laser Lithotripsy The laser was developed in 1960 and the first medium used was the ruby. In 1968, Mulvaney and Beck reported that although the ruby laser could effectively fragment urinary calculi it generated excessive heat and was not appropriate for clinical use.

The first widely available laser lithotrite was the pulsed-dye laser, which employed a coumarin green dye as the liquid laser medium.

The holmium laser wavelength is 2140 nm in the pulsed mode and pulse duration of the holmium laser ranges from 250 to 350 sec.

The long holmium:YAG pulse duration produces an elongated cavitation bubble that generates only a weak shockwave.

holmium laser lithotripsy occurs primarily through a photothermal mechanism that causes stone vaporization

Laser Lithotripsy Advantage:

The holmium laser is one of the safest, most effective, and most versatile intra- corporeal lithotripters.

The ability of the holmium laser to fragment all stones regardless of composition is a clear advantage.

its production of significantly smaller fragments as compared with other lithotrites.

Reduces retropulsion of the stone or stone fragments compared with EHL or pneumatic lithotrites.

The holmium laser is more compact than the coumarin laser, requires minimal maintenance,and is ready for use 1 minute after it is turned on.

Laser Lithotripsy Disadvantage:

The holmium laser is the initial high cost of the device and the cost of the laser fibers.

The fracture of a laser fiber inside of an endoscope can result in a catastrophic failure of the scope, as when this occurs the fiberoptic bundles that transmit images and light are generally destroyed

A potential side effect of holmium laser lithotripsy is the production of cyanide when uric acid stones are treated, which has been reported in vitro

Laser Lithotripsy

Rigid Lithotripters

Ballistic lithotripsy relies on energy generated by the movement of a projectile. The Swiss LithoClast, introduced in the early 1990s, was the first ballistic lithotrite. Following the introduction of the LithoClast, the electrokinetic lithotripter was introduced in the mid 1990s.

There is no significant difference in stone fragmentation, proximal stone migration, and safety margin between LithoClast and electrokinetic lithotripter.

Ballistic Lithotripters

Ballistic Lithotripters Advantage:

The ballistic lithotrites provide an effective means for stone fragmentation in the entire urinary tract, with a wide margin of safety.

Compared with EHL, ultrasonic lithotripsy, and laser lithotripsy, ballistic devices have a significantly lower risk of ureteral perforation.

ballistic lithotrites is their relatively low cost and low maintenance.

Ballistic Lithotripters Disadvantage:

Ballistic is rigid nature of the technology, which requires ureteroscopes or nephroscopes with straight working channels.

Ballistic lithotripsy is associated with a relatively high rate of stone retropulsion.

Teichman and associates (1998b) reported that fragments larger than 4 mm are produced by all types of endoscopic lithotrites, with the exception of the holmium:YAG laser.

Ballistic Lithotripters Technique:

The ballistic lithotripter should be activated only when there is a clear view of the stone and the probe position can be identified.

Fixation of ureteral stones with a basket or proximal placement of a ureteral occlusion balloon is sometimes necessary

The goal of ballistic lithotripsy in the ureter is to generate fragments that are small enough to permit spontaneous passage (

Ultrasonic Lithotripters Mulvaney first reported the use of ultrasound vibrations to break renal calculi in 1953. The ultrasound probe works by applying electrical energy to excite a piezoceramic plate

in the ultrasound transducer. Ultrasonic lithotripsy is more efficient during PNL, owing to the greater flow of irrigant

through the larger diameter ultrasonic probes that can be used. The size, density, and surface structure of the calculus appear to be more important. Auge and associates (2002a) have reported on a new combination intracorporeal

lithotripter that incorporates ballistic lithotripsy and ultrasonic lithotripsy modalities (LithoClast Ultra).

Ultrasonic Lithotripters Advantage:

The efficient combination of stone fragmentation and simultaneous fragment removal.

the minimal risk of serious tissue damage.

Ultrasonic Lithotripters Disadvantage:

The rigid nature of ultrasonic probes and their small diameter limit the appeal of this technology in treatment of ureteral stones.

ureteroscope with a straight working channel is required.

Ultrasonic Lithotripters Technique:

When ultrasonic lithotripsy is applied during PNL the stone should first be trapped between the probe and the urothelium.

The application of gentle pressure to the stone enhances fragmentation

When ureteral stones are treated the ureter may need to be dilated to allow passage of the offset rigid ureteroscope.

the goal of treatment is either to fragment the stone completely or to generate fragments that are small enough to be extracted or passed spontaneously.

Combination Ballistic and Ultrasonic Devices

The first combination device brought to the clinical market was the Lithoclast Ultra (Boston Scientific, Natick, MA) which relied on a combination handpiece.

Pietrow and associates (2003) reported, the stone clearance times were significantly better for the combination device than for the conventional ultrasonic lithotripters.

The Cyberwand (Gyrus ACMI, Southborough, MA) is an intracorporeal lithotripter that relies on a dual ultrasonic probe design that incorporates coaxial high-frequency and low-frequency probes.

Kim and associates (2007) find that the stone penetration time for the Cyberwand was almost twice as rapid as it was for the Lithoclast Ultra.

Conclusion The holmium laser has become the mainstay of ureterorenoscopic lithotripsy by virtue

of its ability to fragment all stones. As well, the use of small-diameter fibers allows access to all areas of the ureter and

intrarenal collecting system. However, for patients with complex, large-volume calculi undergoing PNL, the

combination devices will permit more efficient fragmentation of the stone.

THANK YOU FOR YOUR ATTENTION