What Are the Pros and Cons of Lithotripsy for Kidney Stones?

Extracorporeal shock wave lithotripsy uses a hydroelectric or electromagnetic shock wave generator to emit a high-energy shock wave that penetrates the human body, focuses on urinary tract stones in the body, releases energy to crush the stones, and the stone fragments are naturally discharged with less pain.

Lithotripsy

Intracorporeal lithotripsy (IL) refers to the treatment of lithotripsy inside the human body using special equipment, including mechanical, hydroelectric, ultrasonic, laser, and pneumatic lithotripsy. In the past 20 years, with the improvement of urological equipment and operation technology, IL has made great progress. Although extracorporeal shock wave lithotripsy (ESWL) has become the first choice for the treatment of upper urinary calculi, ESWL is difficult to locate or treat stones and shock wave lithotripsy for lower urinary tract stones, ureteral incarcerated stones, huge kidney stones, etc After the severe stone street, IL is still an essential treatment. For more than 10 years, we have used mechanical, hydroelectric, ultrasonic, and pneumatic ballistic lithotripters to treat urinary tract stones, and inspected various laser lithotripters abroad. Combining our experience and experience, in accordance with the chronological order of the emergence of various lithotripsy, a brief introduction to its principles and applications.

Indication

1. Kidney stones

(1) A single stone is 2cm.

(2) 2 ~ 3cm stone, double J tube can be left before crushing stone.

(3) Mold or multiple stones, comprehensive treatment, that is, percutaneous nephrolithotripsy (PCNL) + extracorporeal shock wave lithotripsy (ESWL) + transurethral ureteroscopy (URS).

(4) Calculus below kidney is less than 1cm.

(5) Refractory stones (calciferous phosphate, cystine, calcium oxalate stones) <1.5cm.

(6) Isolated kidney stones> 1.5 cm. Double J tubes were placed before surgery.

2. Ureteral calculi <1cm.

3 Bladder stones, the condition does not allow surgery or the patient refuses surgery.

4 Urethral stones cannot be pushed into the bladder or lack of lithotripsy and patients refuse surgery.

Contraindications

1. Stones with distal urinary tract obstruction.

2. Matrix stones.

3 Kidney calf diverticulum stones.

Relative contraindication

</ strong> 1. Kidney stones> 2cm.

2. Obese (weight more than double the standard weight).

3 Patients with spinal deformities or limb contractures cannot be positioned as required.

4 The patient was incarcerated with stones.

5. With incurable bleeding disorders.

6. Heart and liver dysfunction.

7. Serum creatinine 265 mol / L.

8. Active period of infectious diseases.

9. Diabetes is not controlled.

10 During pregnancy.

11. Stones in the lower ureter of infertile women prevent ovarian damage; stones in urethra of infertile men should be protected to protect the testes.

1. Asana.

(1) Kidney and proximal ureteral stones are taken in supine position.

(2) Prone position with distal ureteral stones.

(3) Bladder stones are taken in prone or semi-sitting position.

(4) Take a semi-sitting position with urethral stones.

(5) For pediatric patients, they should be properly fixed after anesthesia, and B-mode ultrasonography should be used as far as possible.

2. Positioning. X-ray or B-ultrasonography was used for positive stones, and B-ultrasonography was used for negative stones.

3 Working potential and number of bombardments. It is comprehensively determined according to the wave source, model of the machine, and the location, size, number, and composition of the stones. The general voltage is 8 ~ 14kV, and the number of bombardment is less than 3000 times.

4 X-ray or B-ultrasound monitor is used to observe the lithotripsy in real time.

5. Monitor the patient's vital signs during the operation, observe the patient's response, and make corresponding treatment in time.

ML has a long history, dating back to the ancient Egyptian period. According to records, the method at that time was to fix a diamond or hard stone to one end of a hollow reed rod with glue or asphalt, and then insert the rod into the patient's bladder, allowing the patient to move around, and gradually stoned by the action of the diamond or stone. Crushed. But this method can only treat soft "struvite" (magnesium ammonium phosphate stones), but it can't help harder stones such as calcium oxalate monohydrate stones. In 1782, Indian doctor Martin designed a metal file that can be inserted into the urethra. He successfully cured his bladder stones with this file. In 1824, the French doctor Ciiale invented a three-pronged forceps. He can grasp the bladder stones by touch, pressurize the body with special screws, and finally crush the stones. However, until the 19th century, open surgery (mainly for bladder stones) was popular in continental Europe. Lithotripsy was rarely used because of its low success rate. The advent of cystoscope in 1879 was a milestone in the history of the development of IL. Since then, it has changed the situation of doctors' blind operation and greatly improved the success rate and safety of lithotripsy. Since then, a variety of mechanical lithotripters and lithotripters have been designed, and some are still in use today. There are two main types of lithotripters: clamp type and stamping type. The latter was first designed and applied by Mauermayer and Hartung in 1976. It can flush out the stone fragments at the same time as the crushed stones, so that the surgical field is kept clear. ML is simple and safe to operate. It can break stones of various components with a diameter of less than 3cm. It is mainly used for the treatment of bladder stones. In a few cases, it can also be used for kidney stones. Controlled bleeding.

(electrohydrauticlithotripsy, EHL)

EHL was originally invented by Soviet engineer Yutkin in 1955. After more than 10 years of improvement, a clinical bladder lithotripter called Urat-1 has been introduced. Its basic principle is the same as that used now: there is an insulating layer between two electrodes with different voltages. When the voltage difference between the insulation layers exceeds the maximum resistance of the insulation layer, sparks are generated between the electrodes to form a plasma. Plasma is an ion and electron cavitation bubble that rapidly expands to a certain extent and then disintegrates sharply, forming liquid shock waves and micro-jets, breaking up stones. Using high-speed photography and sound detection technology, it can be found that with each discharge, plasma cavities around the end of the EHL probe oscillate, and three shock waves are generated at the same time. The first shock wave is formed by plasma expansion; the second and third waves are caused by the collapse of cavitation bubbles. When the tip of the probe is about 1 mm from the stone surface, the shock wave generated is the strongest, and the stone crushing effect is the best. If the distance is> 3 mm, the energy of the cavitation bubble will be converted into acoustic energy more, and the stone crushing efficiency will decrease. These observations are consistent with clinical reality.

Due to the limitation of materials in the early days, the discharge time was very long (5-10ms), and the shock wave generated easily damaged the probe and tissue. With the development of electronics and materials science, the discharge time of the current liquid stone crusher is generally 1 ~ 5s, the working voltage is 1 ~ 8kV, and the output energy is 50 ~ 1300mJ. The thickness of the probe has also been reduced from the F10 of Urat-1 to a minimum of F1.6. EHL is non-selective for stone components, and the probe can be bent, which can be used to treat stones in various parts of the urinary system, but there are certain complications, such as ureteral perforation. Studies have shown that, apart from direct mechanical injuries, tissue damage is mainly related to the formation and disintegration of cavitation bubbles, and the degree is directly proportional to the output energy. No evidence of thermal damage has been found. In order to reduce tissue damage, some people have recently added a metal shield to the end of the probe to prevent the surrounding tissue from being directly exposed to the plasma, which has achieved certain results.

The first experiment with ultrasound on lithotripsy was performed by Mulvaney in 1953. The principle is that a transducer made of piezoelectric effect converts electrical energy into mechanical energy (vibration), and then directly transmits the energy to the stone through a metal probe, causing the stone to have high-frequency resonance and then break. Unlike EHL, ultrasonic lithotripsy requires direct contact between the probe and the stone. Because it works through the vibration effect (frequency 20-30kHz, amplitude 15-20m), it has very little damage to normal elastic tissue, so USL is quite safe. However, high-frequency vibration can generate a large amount of heat, which can cause thermal damage to surrounding tissues, so a large amount of circulating water is needed to cool the probe during work. Early ultrasound probes were all hollow, with a thickness of up to F8, so that the scope was removed before it could be used for ureteroscopy. The thickness of the hollow probe currently used is F4.5, which can be operated under ordinary ureteroscopy. The hollow probe is not only used as a water circulation channel, but also used to suck stone fragments. Goodfriend first used solid ultrasound probes in 1973. This probe is thinner (F2.5) and can be used for thinner ureteroscopes with a relatively wide range of applications. The solid probe lithotripsy relies on the lateral vibration of its tip, which is different from the longitudinal vibration of the hollow probe, so the driving effect on stones is significantly reduced. Statistics show that there is no obvious difference in the lithotripsy efficiency of the two probes, but the solid probe is not easy to dissipate heat, the thermal damage is heavy, and it is difficult to handle the stone fragments. The disadvantage of the USL is that the probe cannot be bent and can only be used for rigid mirrors with side mirrors, which limits its scope of application.

Due to the safety of USL, this method is particularly suitable for the treatment of "stone street" after ESWL. Because the stones are tightly wrapped by the surrounding tissue at this time, any other operation can easily cause ureteral perforation. But as long as you try to open the ureter and insert the ureteroscope to the stone, you can break the stone with an ultrasound probe.

The laser appeared in 1960. In 1968, Mulvaney first broke the stones with a ruby laser. Due to too much heat production, which caused severe tissue damage, it was quickly abandoned. Later, continuous wave laser lithotripsy was used, including CO2 laser, neodymium-doped: yttrium aluminum garnet laser (Nd: YAG), etc. CO2 laser can effectively lithotripsy in the air, but the energy decays very quickly in the water. The gas must be perfused into the body during lithotripsy, which is difficult to apply clinically. Although Nd: YAG laser can effectively crush stones in water, the required energy is very high. In addition to causing severe tissue thermal damage, it is also very easy to damage optical fibers. Therefore, such lasers are gradually being phased out. The above-mentioned lasers are all direct lithotripsy using lasers. In the 1980s, pulsed lasers began to replace continuous wave lasers. The former can convert laser energy into shock waves to play a role, so the heating effect is significantly reduced. Clinical application proves that this type of laser has high lithotripsy efficiency and a relatively low incidence of complications. The current lithotripsy lasers are Q-Nd: YAG laser (Q-switchedNd: YAG, Q-Nd: YAG), dye laser (dyelaser, DL), alexandrite laser (AL), ytterbium: YAG laser (Holmium: YAG, Ho: YAG), etc.

Like EHL, the current lithotripsy of all LLs depends on the generation of plasma and shock waves. The difference is that EHL is generated by electrical discharge, while laser light is formed by photolysis. After the stones are irradiated with high-energy and high-density laser light, plasma is rapidly formed on the surface, and then shock waves and micro-jets are generated to break the stones. Different pulse width lasers generate shock waves in different ways. The shortest pulse width of Q-Nd: YAG is mainly due to the expansion of the plasma to form a shock wave; while for the other three lasers, the collapse of the cavitation bubbles is the main reason for the shock wave.

4.1Q-Nd: YAG

</ strong> The principle of laser Q-switching is: use the Q switch to make the Q value of the optical cavity change rapidly, so that it produces very short pulses (ns level) and very high peak power (several million watts), so as to form Shock wave, which converts continuous wave laser to pulsed laser. In 1983, Watson first used Q-Nd: YAG laser lithotripsy, which worked well, but the glass optical fiber at that time could not withstand the high energy required for lithotripsy. In 1989, Hofmann switched to quartz optical fiber and achieved a complete lithotripsy rate of 90%. There was no thermal damage to the tissue. The optical fiber was intact, but it was unable to break the calcium oxalate monolith.

4.2DL

</ strong> This is a pulsed tunable laser specifically designed for lithotripsy. It was first used clinically by Drelter et al. in 1987. DL uses liquid coumarin green dye as the excitation medium. Adjusting the dye can change its wavelength. The laser can be absorbed by most of the stone components, but not absorbed by water, and it can be reflected by the ureter with less absorption, so it can effectively break most of the stones without damaging the ureter. Not good for calcium oxalate monohydrate stones. Cystine stones can reflect a large amount of laser light, it is difficult to form plasma on the stone surface, and the stone crushing effect is not good. In this regard, Tasca (1993) used a method of rifampicin to encapsulate stones (using 2% rifampicin solution as the infusion solution) to enhance the laser absorption of cystine stones and improve the lithotripsy efficiency. Of course, this method can also be used for other laser lithotripsy.

4.3AL

</ strong> Unlike other lasers, the excitation medium for AL is solid. This laser, like the pulse DL, has a shorter pulse width. The physical characteristics and the lithotripsy mechanism of the two are basically the same, and they can be absorbed by most of the calculus components, producing a strong plasma effect and shock wave. The difference is that AL can break hard stones such as cystine stones and calcium oxalate monohydrate. The effect on calcium oxalate dihydrate is not good.

4.4Ho: YAG

</ strong> Ho: YAG is widely used in clinical resection and incision surgery because of its solidification and vaporization of tissues, and shallow penetration depth (<0.5mm). It has been used in lithotripsy since 1993. The physical characteristics and lithotripsy mechanism of Ho: YAG are different from the three lasers mentioned above. Because the wave width is very long, it can be absorbed by water and almost all calculus components, so this laser has a strong gasification effect on water. High-speed photography shows that the cavitation bubbles produced by Ho: YAG are pear-shaped and have a longer retention time (Moss effect), are asymmetric during disintegration, and form a weak shock wave, which is not enough to effectively crush the rock. Studies have shown that its gravel action is mainly based on light and heat effects. It can "drill" holes in stones and "remove" stones rather than "disintegrate" stones. Ho: YAG can break various types of stones, including hard stones such as calcium oxalate monohydrate and cystine stones, with small fragments. Some people have compared Ho: YAG and EHL, and found that under the same conditions (patient age, gender, stone size, composition, etc.), the former's lithotripsy efficiency is higher (97%: 85%). The incidence of complications was similar between the two.

LL has many advantages, such as high lithotripsy efficiency, thin optical fiber and can bend, lighter tissue damage than EHL, etc., but the slow lithotripsy speed is not suitable for large stones, and the composition of the stones has an effect on the lithotripsy effect. In addition, the price of laser equipment is higher than other lithotripsy equipment, which limits its popularity.

5 pneumatic lithotripsy (PL)

</ strong> PL is a new type of lithotripsy, first developed in Switzerland in 1990, so it was named SwissLithoclast. It uses compressed air to drive a projectile in a closed box. The latter hits the bottom of the metal rod connected to the box with a certain frequency (12Hz). The stone is broken by the mechanical movement of the metal rod. Its working principle is the same as that of industrial pneumatic pressure. Like a hammer. Pneumatic lithotripters have different pressure adjustments, up to 300kPa. The stainless steel lithotripsy probe has a variety of models to choose from, which can crush various stones including calcium oxalate monohydrate and cystine stones. A group of in vitro experiments used standard stone models to compare the lithotripsy efficiency of the four lithotripsy methods of USL, EHL, LL, and PL, with the highest PL. Another group of animal experiments also compared the damage of the four types of lithotripsy to the bladder and ureter. It was found that PL and USL were lighter, with only slight epithelial shedding, while EHL and LL caused tearing and necrosis of the epithelium. Therefore, PL is a safe and efficient method of lithotripsy. Like USL, PL probes cannot be bent and can only be used for rigid and semi-rigid endoscopes, but without the pyrogenic effect of ultrasonic lithotripsy probes. In recent years, an improved pneumatic lithotripter, Browne pneumatic lithotripter, has come out. Its nickel-titanium alloy probe can break the stones through a 90 ° bend, which is a promising lithotripter. The disadvantage of PL is that its probe is easy to push stones. This should be paid attention to when ureteral lithotripsy, because moving stones to the proximal end will increase the difficulty of lithotripsy. If necessary, the stones should be fixed with a stone basket first. In addition, PL's stone fragments are relatively large and often need to be used with other instruments such as stone clamps.

Each IL has its advantages and disadvantages. It should be selected clinically according to the existing equipment in the hospital, the operating experience of the doctor and the stone status of the patient. Either one method or two methods can be used in combination, or cooperate with ESWL to learn from each other's strengths and weaknesses, in order to obtain the best lithotripsy effect and cause the least complications.