LASERS IN GENERAL SURGERY
0039-6109/92 $0.00
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BILIARY LASER LITHOTRIPSY Desmond H. Birkett, MD, FACS
Reoperation for the management of retained common duct stones carries a significant morbidity and mortality rate,2, 20, 22, 23, 38 which has prompted the development of a variety of nonoperative methods for the removal of these stones. With T-tube tract access, the stones can be removed by baskets directed fluoroscopically through the tract, as described by Burhenne. 8 However, with improvement in the designs of endoscopes, T-tube tract choledochoscopy has become the preferred method of management of retained biliary stones. 5, 6, 24 When there is no percutaneous access to the biliary tree, endoscopic retrograde cholangiopancreatography (ERCP) and papillotomy, as developed by Classen and Demling,lO is the management of choice. Cotton reports that 90% of stones are small enough to be treated by ERCP and papillotomy, the other 10% being too large for basket extraction without fragmentation.1l Until 10 to 15 years ago, lithotripsy-the fragmentation of stonesrelied completely on mechanical crushing using strong flexible endoscopic baskets, but these methods were not reliable. Currently, there are a number of minimal-access methods of lithotripsy available for use in the biliary system. Ultrasonic lithotripsy is an extremely reliable and rapid method of stone fragmentation, but because of the rigid vibrating hollow rod, it must be applied under direct vision through a rigid endoscope. In the biliary system, it is particularly useful in the gallbladder for fragmenting large stones rapidly through a straight cholecystostomy tract. The preferable methods of stone fragmentation in the biliary tree are electrohydraulic and laser shock wave lithotripsy because the probes are small and flexible and can be used under direct vision through the new generation of small flexible endoscopes. From Boston University School of Medicine; and the Division of Surgery, University Hospital, Boston, Massachusetts
SURGICAL CLINICS OF NORTH AMERICA VOLUME 72· NUMBER 3· JUNE 1992
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The principle of electrohydraulic lithotripsy is the development of a spark generated by the passage of an electrical current between two electrodes embedded in the tip of a fine probe, which generates a shock wave powerful enough to cause stone fragmentation. The sizes of the probes are 1.9 Fr to 9 Fr. Laser shock wave lithotripsy is the transformation of light energy, transmitted via a quartz fiber, into acoustic energy that generates a shock wave sufficient to fragment stones. LASER LITHOTRIPSY: EXPERIMENTAL DATA
In 1981, Orii et al were the first to report the use of a laser to treat two patients with retained common duct stones. 32 Those authors used a continuous-wave Nd:YAG laser discharged via a quartz fiber passed through the center of a basket in which the stone was secured. Fifteen watts of laser energy was applied to the stones for 5 seconds, resulting in fragmentation into two pieces, which were extracted with the basket. In 1983, those authors reported on another nine patients in whom stones were treated with 40 W of continuous-wave Nd:YAG laser energy with resulting fragmentation that aided basket extraction. 33 Chen and Jan report using continuous-wave Nd:YAG laser lithotripsy via a transhepatic route to fragment a bilirubin common duct stone. 9 Orii et al noted that continuous-wave laser lithotripsy is effective only for bilirubin stones, not for cholesterol stones. 33 However, in another study, continuous-wave Nd:YAG laser lithotripsy combined with basket extraction of the fragments was used to treat gallbladder and common duct stones in five patients, with a power setting of 50 W in I-second bursts for cholesterol stones and 30 to 50 W in 0.5-second bursts for bilirubin stones. 26 The small fragments were then basket extracted; a mean of 9.4 lithotripsy sessions (range 2-27) were needed to complete the treatment. In the larger and thicker gallbladder, perforation from heat is less likely to occur. Continuous-wave Nd:YAG laser lithotripsy is only really successful in pigment stones: in cholesterol stones, it tends to drill a hole without producing fragmentation. 16 The continuous-wave Nd:YAG laser converts light energy to heat energy, and this is used palliatively in the gastrointestinal tract to vaporize and necrose tissue to open up a channel through inoperable tumors of the esophagus and rectum. This heat generation raises the distinct possibility of damage to the biliary tree and perforation while fragmenting stones should the laser energy be misdirected from the stone to the wall of the bile ducts. Ell et al demonstrated that in human gallstones in vitro, the continuous-wave Nd:YAG laser results in a thermal melting and drilling effect at 5 to 110 Wand 0.1 to 10 seconds. 16 In an in vitro study, Dayton et al demonstrated that the continuous-wave Nd:YAG laser generates significantly more wall heat than other wavelengths and other laser modes known to fragment stones, the heat being enough to perforate the bile ducts, whereas the copper-vapor and other pulsed lasers produce minimal wall heat. 14
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In an attempt to improve the success of gallstone fragmentation, particularly for cholesterol stones, Ell et al investigated the pulsed Nd:YAG laser in an animal model. 15 They found that at energies of 2 J and a pulse duration of 10 mseconds, fragmentation occurred in a mean time of 4 seconds for stones with a volume of less than 1.5 cc and a mean of 9.5 seconds for stones with a volume greater than 1.5 cc. However, the resulting fragments were large. The measured temperature increase in the surrounding medium was 3° to 100 e, with perforation of the bile duct in one animal, again raising questions about the safety of this laser in a clinical setting. The flashlamp-pulsed Nd:YAG laser effects lithotripsy by converting light into thermal energy. 15 Again, this raises the issue of safety. In one study with the pulsed Nd:YAG laser discharged at a pulse energy of 35 mJ and a pulse duration of 8 nanoseconds, which effectively fragments renal stones, there was minimal injury to the ureter: small craters in the urothelium without the injury reaching to the depth of the muscle. 25 In fact, when discharged at energies four times that needed for stone fragmentation, and for as many as 600 pulses, this laser caused only a small rupture of the urothelium without creating a hole through the wall of the ureter. Similar studies have yet to be performed in the bile duct, which is not as thick as the ureter, but in view of the minor damage confined to the mucosa of the ureter, it is likely that there will be no perforation in the bile duct. The Q-swrtched Nd:YAG laser has a different mechanism of action: it converts light into mechanical energy. It has been found to be effective at fragmenting stones without tissue injury in an animal model. 17 In an in vitro study, Ell et al found that the Q-switched Nd:YAG laser fragmented gallstones in 30 seconds to 5 minutes at a pulse duration of 5 to 20 nanoseconds and a pulse energy of 30 to 50 mJ. 17 There was no tissue injury, and the size of the fragments ranged from grains of sand to grains of rice. Previous attempts at lithotripsy with a Q-switched Nd:YAG laser had failed because of the difficulty of coupling high-energy pulses to small flexible fibers. The Q-switched Nd:YAG laser is not yet acceptable clinically because of the need for high energy densities to effect stone fragmentation, the difficulty of using a coupler between the laser and the fiber to prevent fiber damage, and the need to use large fibers, in the range of 600 ,.,.,m. These disadvantages cause this laser to be less useful clinically than a pulsed-dye laser.4o The need for high energy to cause fragmentation; the heating effect, and therefore the safety issues; and the difficulty of connecting high-energy lasers to small fibers prompted the examination of other wavelengths. The tunable-dye lasers looked the most promising. Nishioka et al examined a series of short-pulse lasers between the wavelengths of 450 and 700 nm and showed that the wavelength with the lowest ablation threshold was 450 nm and that with longer wavelengths, there were greater energy requirements. 31 The breaking off of fragments from the stones was accompanied by a sharp acoustic snap, a bright flash of broad-spectrum light, and a brisk recoil of the quartz
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fiber. Nishioka et al found a pulsed-dye laser operating at 504 nm to be the most effective. In their experience, the mass of stone fragments removed increased with increasing pulse energy, with cholesterol stones requiring more energy than pigment stones for the same rate of fragmentation. The more rapid fragmentation of pigment stones is attributable to better absorption of visible light by the darker stones. 31 The mechanism of action of the pulsed tunable-dye laser is the conversion of light energy into acoustic energy, resulting in the creation of a shock wave. It is thought that a plasma is created at the stone surface, which results in the development of a bubble that expands and subsequently collapses, giving rise to a shock wave. This theory is supported by the work of Teng et aI, who, using time-resolved microsecond photography, demonstrated the development of a bubble at 37 microseconds that reaches a maximum over 250 microseconds before it starts to collapse. 39 The collapsing bubble is accompanied by a plume of debris arising from the stone surface. Because the energy delivered by the laser is too low to cause vaporization of water, the most likely cause of the bubble is a propagating laser-induced acoustic shock wave, which shears the liquid medium near the ablation surface. 39 In animal studies using a flashlamp-pumped tunable pulsed-dye laser emitting at 504 nm with a pulse duration of 1.2 microseconds, stone fragmentation was achieved with pulse energies of 18 to 80 mJ while the stone was held in a laser basket in the common bile duct. 29 The system was found to be relatively safe, with perforation of the common duct wall occurring after 58 pulses at a pulse energy of 60 mJ. When the fiber was held at right angles to and in contact with the duct wall, higher pulse energies resulted in earlier perforation. Murray et al investigated the pulse energy required to fragment biliary stones in vitro using the pulsed-dye laser at 440, 480, 504, 560, 590, and 635 nm. They found that the least energy was needed at the shortest wavelength, with more pulse energy being needed with every increase in wavelength. 29 They also found that predominantly pigment stones were fragmented with a median total energy of 2.2 J and cholesterol stones with 24.2 J, an ll-fold difference that is attributable to the greater absorption of the laser light energy by pigment stones. The duration of the pulse also is important for optimal fragmentation. Bhatta and Nishioki showed that the energy required to fragment biliary stones increases with increasing pulse duration from 1 to 20 microseconds, with acceptable rates of fragmentation around 1 to 8 microseconds, a short pulse duration being optimal. 3 Other wavelengths have been investigated. ReMine and associates examined the fragmentation rate of biliary stones using a holmium laser with a wavelength of 2.1 f.Lm and found that pulse energies greater than 800 mJ have a shattering and blast effect on the stones, whereas pulse energies of 100 mJ drill holes in the stones without causing fragmentation. The optimal energy for fragmentation was 250 mJ.35 Energies greater than 800 mJ resulted in perforations in the common duct, whereas at the optimal pulse energy for fragmentation (250 mJ), there was no mucosal injury.
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The pulsed alexandrite laser emitting at 570 nm has been investigated by several groups, with Strunge and coworkers pointing out that the major problem of fiber tip disintegration is reduced to clinical insignificance by keeping the power density below 125 MW/cm 2 and using pulse durations of 700 nanoseconds or greater. 37 The 308-nm excimer laser has shown promise in angioplasty21 and, as a result, was examined for its effect on the fragmentation of biliary stones by Shi et aI, who found effective fragmentation with fluence levels smaller by a factor ranging from 30 to 200 as compared with the fluence levels needed with the 504-nm pulsed-dye laser.36 As with the pulsed-dye lasers, pigment stones fragmented more readily than cholesterol stones, almost certainly because of the higher absorption rate of the pigment stone. The effect on tissue has yet to be investigated, and, as a result, the possible place of this laser in clinical practice is not known. The coumarin pulsed-dye laser emitting at 504 nm with pulsed energies of 50 to 80 mJ and a pulse duration of 2 microseconds effectively fragments stones and in the dog ureter was shown to cause only small mucosal lesions without perforation of the ureter wall. 42 Our data on the tissue effects of this laser were developed in an in vitro porcine model using pulse energies of 60 and 120 mJ.7 With the fiber held at right angles and in direct contact with the tissue, perforations of the bile duct occurred after 50 consecutive pulses in 11.1% of ducts at 60 mJ and in 44.4% at 120 mJ. Although a variety of lasers have been shown to fragment biliary stones, the most effective is a system that avoids the conversion of light into heat but rather converts light into acoustical energy that results in effective fragmentation with little chance of surrounding tissue damage. Further desirable qualities are a low pulse energy and a high light absorption rate by the stone for the most efficient fragmentation. Currently, the best system is the coumarin pulsed-dye laser emitting at 504 nm with a pulse duration of around 1.5 to 2 microseconds. As other wavelengths are developed and studied, this view may change. The alexandrite and the excimer pulsed lasers show early promise. CLINICAL APPLICATION OF LASER LITHOTRIPSY
The introduction of nonoperative methods of treatment for retained common duct stones was a significant advance over reoperation, with its significant morbidity and mortality rates. Initially, these techniques involved the passage of instruments down aT-tube tract with blind grasping of the stones. The introduction of ERCP and papillotomy by Classen and Demling in 1974 resulted in an important advance for the management of common bile duct stones,lO permitting the removal of as many as 90% of such stones. 11 In patients with access to the common bile duct via a T-tube tract, flexible choledochoscopy with basket extraction is an excellent alternative. 5, 6, 24, 27 However, with both tech-
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niques, there is a failure rate secondary to too large a stone. In this situation, fragmentation is needed to aid stone removal. Mechanical lithotripsy with a strong basket is a cumbersome and traumatic method that at times fails because of breaking of the basket or nonfragmentation. Electrohydraulic lithotripsy used through a flexible instrument, with the smallest probes being 1.9 Fr and the larger probes 3 Fr, is effective. There is an incidence of duct injury if the probe is inadvertently discharged on the wall of the duct. We showed in the porcine model that perforation of the common bile duct can occur with as few as three pulses if the probe is in direct contact with the tissue surface. 7 This incidence of duct perforation may be reduced by the introduction of a shielded electrohydraulic lithotripsy probe, which has proved to be safer in the animal model.4 Two of the advantages of laser-induced shock wave lithotripsy are the small quartz fibers (200-320 ....m) that can be passed through the instrument channels of small endoscopes and its comparative safety. The advantages of small fibers, safety, and an instrument that can be used in the urinary as well as the biliary system make this an attractive technology despite its greater cost in comparison with other forms of lithotripsy. Despite a considerable volume of experimental work on biliary lithotripsy, its use clinically is limited and in an early stage of development. The first clinical report of laser lithotripsy was in 1981 by Orii et aI, who used a continuous-wave Nd:YAG laser in conjunction with T-tube choledochoscopy successfully in two patients with retained common bile duct stones. 32 As noted previously, those authors later reported the complication-free use of the same laser in 11 patients with intrahepatic and common duct stones. 33 Chen and Jan described the use of a continuous-wave Nd:YAG laser in the treatment of common duct stones using a T-tube tract and a transhepatic route in two patients. The only complication was a complaint of a burning sensation by both patients. 9 Inui et al used the continuous-wave Nd:YAG laser to treat 11 patients with symptomatic gallbladder stones by a percutaneous transhepatic route using a flexible choledochoscope. 26 The first successful endoscopic retrograde endoscopic laser lithotripsy of a common duct stone was reported in 1986 by Lux et aI, who used a pulsed Nd:YAG laser, a much safer instrument because of the lower heat production. 28 In a further report, the same group described nine patients with common duct stones treated with the flashlamppulsed Nd:YAG laser.16 Stones were broken up and the fragments extracted by basket in six patients; however, in two patients, the fragments could not be extracted, and in one patient, the stone could not be fragmented at all; these three patients underwent an operation to complete their treatment. Fragmentation was performed under fluoroscopy following endoscopic retrograde papillotomy, with the laser fiber being controlled and placed in contact with the stone by one of two methods. In one method, the stone was trapped in a laser basket and the fiber passed down the center of the basket, keeping it away from the duct wall; in the other method, a laser catheter with a balloon
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on the end was used to keep the fiber away from the wall and in contact with the stone. The "mother and daughter" retrograde endoscopic system was used in one patient to place the fiber on the stone under direct vision. Wenk and coworkers treated symptomatic gallbladder stones via a transhepatic route, using a pulsed Nd:YAG laser followed by basket and suction removal of the fragmentsY There are several disadvantages of the pulsed Nd:YAG system: the mechanism of action is the conversion of light energy into heat, which raises the issue of heat perforation of the common bile duct; and fragmentation results in the production of relatively large pieces that then have to be basket extracted. 16 For satisfactory clinical application, a more effective system is required, one that will fragment stones into small particles that are more likely to pass through the sphincter of Oddi, reducing the need for basket extraction. Although the Q-switched Nd:YAG laser has been used successfully and safely in S6 patients with renal and ureteral stones,I2 its use clinically in the biliary tree is not yet accepted. The largest experience in the literature has been generated using a S04-nm coumarin flashlamp-pumped pulsed-dye laser, of which there are two systems approved by the Food and Drug Administration for use in the United States: the Pulsolith (Technomed International, Danvers, Massachusetts) and the MDL 2000 (Candela Corporation, Wayland, Massachusetts). Cotton and Kozarek reported in 1988 the use of a coumarin dye laser emitting at S04 nm to treat seven patients using a peroral route with a "mother and daughter" endoscopic system to fragment common duct stones. 12 Using 30 to 60 mJ of energy passed through a 2S0-fLm quartz fiber, they were able to fragment stones in all patients with 20 to 2029 pulses. However, they were able to clear the duct in only four patients. Feldman and associates reported the use of the coumarin pulsed-dye laser to fragment a 2-cm intrahepatic stone via a percutaneous tract after a partial left hepatectomy. IS Using a fluoroscopically guided basket, through the center of which a 2S0-fLm quartz fiber could be passed, the stone was secured and fragmented with 60 mJ of energy using SOO pulses. The fragments were irrigated down the left hepatic duct. However, on a cholangiogram the next day, three small fragments were seen. These were basket extracted, with the majority of the other fragments being washed through the sphincter of Oddi into the duodenum. Berci et al report the treatment of a patient with a retained stone in the left hepatic duct using a coumarin pulseddye laser. 1 The stone was 4 to S mm in diameter and was found on a postoperative T-tube cholangiogram. The stone was treated with laser lithotripsy under direct vision using a flexible endoscope passed through the T-tube tract. Flowers and associates report a case of a patient with a 2.S-cm stone in the right hepatic duct that was approached by a transhepatic route. 19 The stone was fragmented with the coumarin dye laser. However, the procedure was terminated because of its length before complete fragmentation had been achieved. One week later, the biliary tract was cleared completely using ultrasonic lithotripsy, which is faster
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at fragmenting stones than the coumarin dye laser. The size and number of stones can be a problem with coumarin pulsed-dye laser lithotripsy, as it produces small fragments rather than the bigger fragments that result with other techniques. This means that fragmentation of a large stone volume, be it a single large stone or multiple smaller stones, may take a long time. Cotton and coworkers report 25 complex instances of common duct stones that either were large or would not respond to other forms of nonoperative management. 13 Five patients were treated under direct vision with the laser fiber passed through a flexible choledochoscope at the time of T-tube tract choledochoscopy, and one patient was treated through the T-tube tract using a basket with a central lumen for the laser fiber. The other 19 patients were treated with retrograde endoscopy through the papilla of Vater after a sphincterotomy, using the "mother and daughter" endoscopic system in 12 patients and, in 7 patients, under fluoroscopy using either a balloon or a laser basket system. All patients were treated using a 200-J,Lm fiber and a pulse energy of 60 mJ at 5 to 10 Hz until complete stone fragmentation or a maximum of 3500 pulses. In only 24 patients could the stone be targeted accurately and, therefore, treated. Of these, fragmentation occurred in 23 patients. Ducts were cleared subsequently in 20 patients, with only one endoscopy session being required in 12 patients. There were no major complications and one minor complication, transient bleeding through the papillotomy, which stopped spontaneously. In the five failures, other treatment plans were required. In another large series, reported by Ponchon and associates, 25 patients with bile duct stones who had failed basket extraction and mechanical lithotripsy were treated with the coumarin pulsed-dye laser.34 After undergoing a preliminary endoscopic sphincterotomy, all patients were treated via a variety of access routes: aT-tube tract in seven patients, with four of these having stones in the common duct and three in the intrahepatic ducts; a retrograde endoscopic route using either a basket or a balloon for laser fiber placement under fluoroscopy in 14 patients; and a transhepatic percutaneous route in four patients. In the seven patients treated via aT-tube tract, the stones were broken up with laser energy into at least two fragments of similar size, which were then either irrigated or pushed through the sphincterotomy site; duct clearance was achieved in all patients. The other patients were treated by retrograde endoscopy unless the stones were intrahepatic. A basket with a central lumen for a laser fiber was used in five patients, and a balloon catheter to keep the fiber tip away from the common duct wall was used in nine patients. The procedure was successful only at clearing the common duct in five patients and, of the nine patients in whom the treatment failed, two underwent operation, one received extracorporal shock wave lithotripsy, and the remaining six were treated successfully with a percutaneous transhepatic technique. In four patients with intrahepatic stones, a percutaneous transhepatic route was chosen as the primary method of delivering laser lithotripsy. In these patients, a 15-Fr transhepatic tract was developed over a 3-week period
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through which a lS-Fr choledochoscope was passed to deliver the laser lithotripsy. In the latter few patients, the tract was dilated at the initial session and a 12-Fr sheath passed, through which a 10.S-Fr endoscope was inserted. In all patients treated by the transhepatic approach, the biliary tree was cleared completely of stones. There were no reported complications of laser lithotripsy with any of the approaches. However, there were three septic episodes related to biliary endoscopy. Ponchon et al point out that the positioning of the fiber against the stone is of critical importance and think that the failure rate of the fluoroscopically directed laser lithotripsy was attributable to the difficulty in establishing a good contact between the fiber and the stone. They feel that positioning is best done endoscopically.34 We have performed laser lithotripsy using a S04-nm coumarin pulsed-dye laser, the Pulsolith, for the fragmentation of gallstones using a variety of percutaneous approaches to the biliary tract. We treated eight patients with T-tube tract choledochoscopy who had been found on postoperative T-tube cholangiography to have retained bile duct stones. Five patients had extrahepatic stones, two had intrahepatic stones, and one patient had both (Fig. 1). Laser lithotripsy was delivered by a 320-j.Lm quartz fiber passed through a 4.9-mm flexible choledochoscope using pulse energies of 100 to 120 mJ at 3 to 5 Hz. All stones were fragmented with between 207 and 2718 pulses. The resulting fragments were small enough to be washed through the sphincter of Oddi into the duodenum, with no fragments having to be removed by basket extraction; no patient had had a prior sphincterotomy. In four of five poor-risk patients, we used laser lithotripsy delivered endoscopically by a transhepatic approach to clear the biliary tree of stones. In two of the patients, a chronic transhepatic tract established over a 3-week period was used to pass a 3.S-mm flexible endoscope (Olympus Corporation, New Hyde Park, New York), and in the other three patients, an acute tract was used. Pulse energies of 100 to 140 mJ at 3 to 5 Hz were delivered in 809 to 4800 pulses. The failure was in a patient who had a fatal myocardial infarction after partial clearance at the first endoscopic treatment session and just prior to a second scheduled treatment. The myocardial infarction was thought to be unrelated to the laser lithotripsy. Three of the four patients treated successfully required two sessions to clear the biliary tree completely of stones. One patient who had had a cholecystostomy and stone removal performed operatively for acute cholecystitis was referred with a stone in a long cystic duct. Transcholecystic endoscopy of the cystic duct was performed using an 8.3-Fr flexible ureteroscope, the ACMI AUR8 (Circon/ACMI, Inc., Stamford, Connecticut), and under direct vision, the stone was fragmented completely and the fragments washed into the cystic duct using pulse energies of 110 mJ at 3 Hz for 170 pulses (Fig. 2). In two patients with gallbladder stones after the placement of a cholecystostomy tube for acute cholecystitis, we used the coumarin pulsed-dye laser through a 4.9-mm flexible choledochoscope (Olympus
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Figure 1. A patient with a stone in a branch of the right hepatic duct who was treated successfully with laser lithotripsy.
Corporation) and fragmented a large stone in one patient with basket extraction of the fragments. However, in the other patient, because of the slow rate of laser fragmentation of a large stone, treatment was completed with the ultrasonic lithotripter. Laparoscopic cholecystectomy is fast becoming an acceptable method for treating symptomatic biliary stones. However, it will not be accepted universally until the common duct can be cleared of stones at the time of laparoscopic cholecystectomy, thus avoiding the too common endoscopic retrograde papillotomy. We have used cystic duct choledochoscopy at the time of laparoscopic cholecystectomy to clear the common bile duct of a stone seen on intraoperative cholangiography. This was achieved by passing a 320-mm quartz fiber attached to
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Figure 2. A patient treated with laser lithotripsy for a small stone remaining in the cystic duct after operative cholecystostomy.
a 504-nm coumarin pulsed-dye laser through the instrument channel of an AUR8 ureteroscope to perform lithotripsy (Fig. 3). Laser lithotripsy is slower than other lithotripsy techniques for fragmenting biliary stones, particularly large stones. It is not the ideal management technique for gallbladder stones, as these stones tend to be larger and the cholecystostomy tracts usually large and straight, making the faster ultrasonic lithotripsy the method of choice. Laser lithotripsy is the method of choice for bile duct stones that cannot be extracted easily with a basket because it breaks stones into small fragments that will pass spontaneously, it is safe, the fibers are small and flexible, and it can be used under direct vision through small endoscopes. It is a technology that significantly enhances minimalaccess biliary procedures.
SUMMARY
Laser lithotripsy is an excellent method of fragmenting those biliary stones that cannot be removed easily by less technically advanced methods such as basket extraction. The energy can be delivered through fine flexible fibers, around 200 to 320 f.Lm in diameter, that can be
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Figure 3. An obese patient who had failure of two endoscopic retrograde papiliotomies prior to laparoscopic cholecystectomy and who underwent successful cystic duct choledochoscopyand laser lithotripsy at the time of laparoscopic cholecystectomy.
passed through the channels of a variety of small endoscopes. Currently, the optimal laser seems to a pulsed system because of the conversion of light to acoustic energy with minimal heating of the surrounding tissues, thus avoiding the chance of tissue injury and perforation. The best wavelength seems to be 504 nm, because at this wavelength, there is maximum absorption of laser energy by pigment stones, resulting in fragmentation using low-energy pulses. With further research, optimal wavelengths and pulse durations may emerge. References 1. Berd G, Hamlin JA, Grundfest W, et al: Percutaneous endoscopic laser lithotripsy of
retained stones in the left hepatic duct. Surg Endosc 4:36-38, 1990 2. Bergdahl L, Holmlund DEW: Retained common duct stones. Acta Chir Scand 142:145149, 1976 3. Bhcitta KM, Nishioka NS: Effect of pulse duration on microsecond-domain laser lithotripsy. Lasers Surg Med 9:454-457, 1989 4. Bhatta KM, Rosen 01, Flotte TJ, et al: Effect of shielded or unshielded laser and electrohydraulic lithotripsy on rabbit bladder. J Uroll43:857-860, 1990 5. Birkett DH, Williams LF Jr: Choledochoscopic removal of retained common duct stones via the T-tube tract. Am J Surg 139:531-534, 1980
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6. Birkett DH, Williams LF Jr: Post-operative fiberoptic choledochoscopy: A useful surgical adjunct. Ann Surg 194:630-634, 1987 7. Birkett DH, Lamont JS, O'Keane JC, et al: Comparison of a pulsed dye laser and electrohydraulic lithotripsy on porcine gallbladder and common duct in vitro. Lasers Surg Med, in press 8. Burhenne HJ: Non-operative retained biliary tract stone extraction: A new roentgenologic technique. AJR 117:377-388, 1973 9. Chen MF, Jan YY: Percutaneous transhepatic cholangioscopic lithotripsy. Br J Surg 77:530-532, 1990 10. Classen M, Demling 1: Endoskopische Sphinkterotomie der Papilla Vateri und Steinextraktion aus dem Ductus choledochus. Deutsch Med Wochenschr 99:496, 1974 11. Cotton PB: Endoscopic management of bile duct stones (apples and oranges). Gut 25:587-597, 1984 12. Cotton PB, Kozarek RA: Laser lithotripsy of large bile duct stones under direct vision via peroral choledochoscopy [abstract]. Gut 29:A1496, 1988 13. Cotton PB, Kozarek RA, Schapiro RH, et al: Endoscopic laser lithotripsy of large bile duct stones. Gastroenterology 99:1128-1133, 1990 14. Dayton M, Decker DL, McCleane R, et al: Copper vapor laser fragmentation of gallstones: In vitro measurement of wall heat transmission. J Surg Res 45:90-95, 1988 15. Ell Ch, Hochberger J, Muller 0, et al: Laser lithotripsy of gallstones by means of a pulsed neodymium-YAG laser: In vitro and animal experiments. Endoscopy 18:9294, 1986 16. Ell Ch, Lux G, Hochberger J, et al: Laser lithotripsy of common bile duct stones. Gut 29:746-751, 1988 17. Ell Ch, Wondrazek F, Frank F, et al: Laser-induced shockwave lithotripsy of gallstones. Endoscopy 18:95-96, 1986 18. Feldman RK, Freeny PC, Kozarek RA: Pancreatic and biliary calculi: Percutaneous treatment with tuneable dye laser lithotripsy. Radiology 174:793-795, 1990 19. Flowers BF, Saslawsky MJ, Mathes GL, et al: The use of the pulsed dye laser and ultrasonic lithotriptor for the removal of multiple intrahepatic gallstones. Surg Gynecol Obstet 170:443-444, 1990 20. Glenn F: Retained calculi within the biliary ductal system. Ann Surg 179:528-538, 1974 21. Grundfest WS, Litvack F, Forrester JS, et al: Laser ablation of human atherosclerosis plaque without adjacent tissue damage. J Am Coli Cardiol 5:929-933, 1985 22. Hall RC, Sakiyalak P, Kim SK, et al: Failure of operative cholangiography to prevent retained common duct stones. Am J Surg 125:51-63, 1973 23. Hicken NF, McAllister AJ: Operative cholangiography as an aid in reducing the incidence of "overlooked" common bile duct stones: A study of 1,293 choledochotomies. Surgery 55:753-758, 1964 24. Hieken T, Birkett DH: Post-operative T-tube tract choledochoscopy. Am J Surg 163:28-31, 1992 25. Hofmann R, Hartung R, Geissdorfer K, et al: Laser induced shock wave lithotripsy: Biologic effects of nanosecond pulses. J Urol 139:1077-1079, 1988 26. Inui K, Nakazawa 5, Naito Y, et al: Nonsurgical treatment of cholecystolithiasis with percutaneous transhepatic cholecystoscopy. Am J Gastroenterol 83:1124-1127, 1988 27. Josephs LG, Birkett DH: Laser lithotripsy for the management of retained common duct stones. Am J Surg, in press 28. Lux G, Ell C, Hochberger J, et al: The first endoscopic retrograde lithotripsy of common bile duct stones in man using a pulsed neodymium YAG laser. Endoscopy 18:144-145, 1986 29. Murray A, Basu R, Fairclough PO, et al: Gallstone lithotripsy with the pulsed dye laser: In vitro studies. Br J Surg 76:457-460, 1989 30. Nishioka NS, Kelsey PB, Kibbi A-G, et al: Laser lithotripsy: Animal studies of safety and efficacy. Lasers Surg Med 8:357-362, 1988 31. Nishioka NS, Levins Pc, Murray Sc, et al: Fragmentation of biliary calculi with tuneable dye lasers. Gastroenterology 93:250-255, 1987 32. Orii K, Nakahara A, Takase Y, et al: Choledocholithotomy by YAG laser with a choledochofiberscope: Case reports of two patients. Surgery 90:120-122, 1981
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33. Orii K, Ozaki A, Takase Y, et al: Lithotripsy of intrahepatic and choledochal stones with YAG laser. Surg Gynecol Obstet 156:485-488, 1983
34. Ponchon T, Gagnon P, Valette p-J, et al: Pulsed dye laser lithotripsy of bile duct stones. Gastroenterology 100:1730-1736, 1991 35. ReMine SG, Aritz TH, Setzer SE, et al: Holmium laser (2.1j.l.) for biliary stone dissolution and ductal tissue effects. Lasers Surg Med 8:191, 1988 36. Shi W, Papaioannou T, Daykhovsky L, et al: Fragmentation of biliary stones with a 308 nm. excimer laser. Lasers Surg Med 10:284-290, 1990 37. Strunge C, Brinkman R, Flemming G, et al: Interspersion of fragmented fiber's splinters into tissue during pulsed alexandrite laser lithotripsy. Lasers Surg Med 11:183-187, 1991 38. Smith SW, Engle B, Averbrook B, et al: Problems of retained and recurrent common duct stones. JAMA 164:231, 1957 39. Teng P, Nishioka NS, Farinelli WA, et al: Microsecond-long flash photography of laser-induced ablation of biliary and urinary calculi. Lasers Surg Med 7:394-397, 1987 40. Thomas S, Pensel J, Englhardt R, et al: The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy. Lasers Surg Med 8:363-370, 1988
41. Wertk H, Thomas ST, Schmeller N, et al: Percutaneous transhepatic cholecystolithotripsy. Endoscopy 21:221-222, 1989 42. Zerbid M, Steg A, Moissonier P, et al: Effects of pulsed dye laser lithotripsy on tissue: Experimental study in canine ureter. Urol Clin North Am 15:547-550, 1988
Address reprint requests to Desmond H. Birkett, MD, FACS Division of Surgery University Hospital 88 East Newton Street Boston, MA 02118
0039-6109/92 $0.00
+ .20
BILIARY LASER LITHOTRIPSY Desmond H. Birkett, MD, FACS
Reoperation for the management of retained common duct stones carries a significant morbidity and mortality rate,2, 20, 22, 23, 38 which has prompted the development of a variety of nonoperative methods for the removal of these stones. With T-tube tract access, the stones can be removed by baskets directed fluoroscopically through the tract, as described by Burhenne. 8 However, with improvement in the designs of endoscopes, T-tube tract choledochoscopy has become the preferred method of management of retained biliary stones. 5, 6, 24 When there is no percutaneous access to the biliary tree, endoscopic retrograde cholangiopancreatography (ERCP) and papillotomy, as developed by Classen and Demling,lO is the management of choice. Cotton reports that 90% of stones are small enough to be treated by ERCP and papillotomy, the other 10% being too large for basket extraction without fragmentation.1l Until 10 to 15 years ago, lithotripsy-the fragmentation of stonesrelied completely on mechanical crushing using strong flexible endoscopic baskets, but these methods were not reliable. Currently, there are a number of minimal-access methods of lithotripsy available for use in the biliary system. Ultrasonic lithotripsy is an extremely reliable and rapid method of stone fragmentation, but because of the rigid vibrating hollow rod, it must be applied under direct vision through a rigid endoscope. In the biliary system, it is particularly useful in the gallbladder for fragmenting large stones rapidly through a straight cholecystostomy tract. The preferable methods of stone fragmentation in the biliary tree are electrohydraulic and laser shock wave lithotripsy because the probes are small and flexible and can be used under direct vision through the new generation of small flexible endoscopes. From Boston University School of Medicine; and the Division of Surgery, University Hospital, Boston, Massachusetts
SURGICAL CLINICS OF NORTH AMERICA VOLUME 72· NUMBER 3· JUNE 1992
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The principle of electrohydraulic lithotripsy is the development of a spark generated by the passage of an electrical current between two electrodes embedded in the tip of a fine probe, which generates a shock wave powerful enough to cause stone fragmentation. The sizes of the probes are 1.9 Fr to 9 Fr. Laser shock wave lithotripsy is the transformation of light energy, transmitted via a quartz fiber, into acoustic energy that generates a shock wave sufficient to fragment stones. LASER LITHOTRIPSY: EXPERIMENTAL DATA
In 1981, Orii et al were the first to report the use of a laser to treat two patients with retained common duct stones. 32 Those authors used a continuous-wave Nd:YAG laser discharged via a quartz fiber passed through the center of a basket in which the stone was secured. Fifteen watts of laser energy was applied to the stones for 5 seconds, resulting in fragmentation into two pieces, which were extracted with the basket. In 1983, those authors reported on another nine patients in whom stones were treated with 40 W of continuous-wave Nd:YAG laser energy with resulting fragmentation that aided basket extraction. 33 Chen and Jan report using continuous-wave Nd:YAG laser lithotripsy via a transhepatic route to fragment a bilirubin common duct stone. 9 Orii et al noted that continuous-wave laser lithotripsy is effective only for bilirubin stones, not for cholesterol stones. 33 However, in another study, continuous-wave Nd:YAG laser lithotripsy combined with basket extraction of the fragments was used to treat gallbladder and common duct stones in five patients, with a power setting of 50 W in I-second bursts for cholesterol stones and 30 to 50 W in 0.5-second bursts for bilirubin stones. 26 The small fragments were then basket extracted; a mean of 9.4 lithotripsy sessions (range 2-27) were needed to complete the treatment. In the larger and thicker gallbladder, perforation from heat is less likely to occur. Continuous-wave Nd:YAG laser lithotripsy is only really successful in pigment stones: in cholesterol stones, it tends to drill a hole without producing fragmentation. 16 The continuous-wave Nd:YAG laser converts light energy to heat energy, and this is used palliatively in the gastrointestinal tract to vaporize and necrose tissue to open up a channel through inoperable tumors of the esophagus and rectum. This heat generation raises the distinct possibility of damage to the biliary tree and perforation while fragmenting stones should the laser energy be misdirected from the stone to the wall of the bile ducts. Ell et al demonstrated that in human gallstones in vitro, the continuous-wave Nd:YAG laser results in a thermal melting and drilling effect at 5 to 110 Wand 0.1 to 10 seconds. 16 In an in vitro study, Dayton et al demonstrated that the continuous-wave Nd:YAG laser generates significantly more wall heat than other wavelengths and other laser modes known to fragment stones, the heat being enough to perforate the bile ducts, whereas the copper-vapor and other pulsed lasers produce minimal wall heat. 14
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In an attempt to improve the success of gallstone fragmentation, particularly for cholesterol stones, Ell et al investigated the pulsed Nd:YAG laser in an animal model. 15 They found that at energies of 2 J and a pulse duration of 10 mseconds, fragmentation occurred in a mean time of 4 seconds for stones with a volume of less than 1.5 cc and a mean of 9.5 seconds for stones with a volume greater than 1.5 cc. However, the resulting fragments were large. The measured temperature increase in the surrounding medium was 3° to 100 e, with perforation of the bile duct in one animal, again raising questions about the safety of this laser in a clinical setting. The flashlamp-pulsed Nd:YAG laser effects lithotripsy by converting light into thermal energy. 15 Again, this raises the issue of safety. In one study with the pulsed Nd:YAG laser discharged at a pulse energy of 35 mJ and a pulse duration of 8 nanoseconds, which effectively fragments renal stones, there was minimal injury to the ureter: small craters in the urothelium without the injury reaching to the depth of the muscle. 25 In fact, when discharged at energies four times that needed for stone fragmentation, and for as many as 600 pulses, this laser caused only a small rupture of the urothelium without creating a hole through the wall of the ureter. Similar studies have yet to be performed in the bile duct, which is not as thick as the ureter, but in view of the minor damage confined to the mucosa of the ureter, it is likely that there will be no perforation in the bile duct. The Q-swrtched Nd:YAG laser has a different mechanism of action: it converts light into mechanical energy. It has been found to be effective at fragmenting stones without tissue injury in an animal model. 17 In an in vitro study, Ell et al found that the Q-switched Nd:YAG laser fragmented gallstones in 30 seconds to 5 minutes at a pulse duration of 5 to 20 nanoseconds and a pulse energy of 30 to 50 mJ. 17 There was no tissue injury, and the size of the fragments ranged from grains of sand to grains of rice. Previous attempts at lithotripsy with a Q-switched Nd:YAG laser had failed because of the difficulty of coupling high-energy pulses to small flexible fibers. The Q-switched Nd:YAG laser is not yet acceptable clinically because of the need for high energy densities to effect stone fragmentation, the difficulty of using a coupler between the laser and the fiber to prevent fiber damage, and the need to use large fibers, in the range of 600 ,.,.,m. These disadvantages cause this laser to be less useful clinically than a pulsed-dye laser.4o The need for high energy to cause fragmentation; the heating effect, and therefore the safety issues; and the difficulty of connecting high-energy lasers to small fibers prompted the examination of other wavelengths. The tunable-dye lasers looked the most promising. Nishioka et al examined a series of short-pulse lasers between the wavelengths of 450 and 700 nm and showed that the wavelength with the lowest ablation threshold was 450 nm and that with longer wavelengths, there were greater energy requirements. 31 The breaking off of fragments from the stones was accompanied by a sharp acoustic snap, a bright flash of broad-spectrum light, and a brisk recoil of the quartz
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fiber. Nishioka et al found a pulsed-dye laser operating at 504 nm to be the most effective. In their experience, the mass of stone fragments removed increased with increasing pulse energy, with cholesterol stones requiring more energy than pigment stones for the same rate of fragmentation. The more rapid fragmentation of pigment stones is attributable to better absorption of visible light by the darker stones. 31 The mechanism of action of the pulsed tunable-dye laser is the conversion of light energy into acoustic energy, resulting in the creation of a shock wave. It is thought that a plasma is created at the stone surface, which results in the development of a bubble that expands and subsequently collapses, giving rise to a shock wave. This theory is supported by the work of Teng et aI, who, using time-resolved microsecond photography, demonstrated the development of a bubble at 37 microseconds that reaches a maximum over 250 microseconds before it starts to collapse. 39 The collapsing bubble is accompanied by a plume of debris arising from the stone surface. Because the energy delivered by the laser is too low to cause vaporization of water, the most likely cause of the bubble is a propagating laser-induced acoustic shock wave, which shears the liquid medium near the ablation surface. 39 In animal studies using a flashlamp-pumped tunable pulsed-dye laser emitting at 504 nm with a pulse duration of 1.2 microseconds, stone fragmentation was achieved with pulse energies of 18 to 80 mJ while the stone was held in a laser basket in the common bile duct. 29 The system was found to be relatively safe, with perforation of the common duct wall occurring after 58 pulses at a pulse energy of 60 mJ. When the fiber was held at right angles to and in contact with the duct wall, higher pulse energies resulted in earlier perforation. Murray et al investigated the pulse energy required to fragment biliary stones in vitro using the pulsed-dye laser at 440, 480, 504, 560, 590, and 635 nm. They found that the least energy was needed at the shortest wavelength, with more pulse energy being needed with every increase in wavelength. 29 They also found that predominantly pigment stones were fragmented with a median total energy of 2.2 J and cholesterol stones with 24.2 J, an ll-fold difference that is attributable to the greater absorption of the laser light energy by pigment stones. The duration of the pulse also is important for optimal fragmentation. Bhatta and Nishioki showed that the energy required to fragment biliary stones increases with increasing pulse duration from 1 to 20 microseconds, with acceptable rates of fragmentation around 1 to 8 microseconds, a short pulse duration being optimal. 3 Other wavelengths have been investigated. ReMine and associates examined the fragmentation rate of biliary stones using a holmium laser with a wavelength of 2.1 f.Lm and found that pulse energies greater than 800 mJ have a shattering and blast effect on the stones, whereas pulse energies of 100 mJ drill holes in the stones without causing fragmentation. The optimal energy for fragmentation was 250 mJ.35 Energies greater than 800 mJ resulted in perforations in the common duct, whereas at the optimal pulse energy for fragmentation (250 mJ), there was no mucosal injury.
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The pulsed alexandrite laser emitting at 570 nm has been investigated by several groups, with Strunge and coworkers pointing out that the major problem of fiber tip disintegration is reduced to clinical insignificance by keeping the power density below 125 MW/cm 2 and using pulse durations of 700 nanoseconds or greater. 37 The 308-nm excimer laser has shown promise in angioplasty21 and, as a result, was examined for its effect on the fragmentation of biliary stones by Shi et aI, who found effective fragmentation with fluence levels smaller by a factor ranging from 30 to 200 as compared with the fluence levels needed with the 504-nm pulsed-dye laser.36 As with the pulsed-dye lasers, pigment stones fragmented more readily than cholesterol stones, almost certainly because of the higher absorption rate of the pigment stone. The effect on tissue has yet to be investigated, and, as a result, the possible place of this laser in clinical practice is not known. The coumarin pulsed-dye laser emitting at 504 nm with pulsed energies of 50 to 80 mJ and a pulse duration of 2 microseconds effectively fragments stones and in the dog ureter was shown to cause only small mucosal lesions without perforation of the ureter wall. 42 Our data on the tissue effects of this laser were developed in an in vitro porcine model using pulse energies of 60 and 120 mJ.7 With the fiber held at right angles and in direct contact with the tissue, perforations of the bile duct occurred after 50 consecutive pulses in 11.1% of ducts at 60 mJ and in 44.4% at 120 mJ. Although a variety of lasers have been shown to fragment biliary stones, the most effective is a system that avoids the conversion of light into heat but rather converts light into acoustical energy that results in effective fragmentation with little chance of surrounding tissue damage. Further desirable qualities are a low pulse energy and a high light absorption rate by the stone for the most efficient fragmentation. Currently, the best system is the coumarin pulsed-dye laser emitting at 504 nm with a pulse duration of around 1.5 to 2 microseconds. As other wavelengths are developed and studied, this view may change. The alexandrite and the excimer pulsed lasers show early promise. CLINICAL APPLICATION OF LASER LITHOTRIPSY
The introduction of nonoperative methods of treatment for retained common duct stones was a significant advance over reoperation, with its significant morbidity and mortality rates. Initially, these techniques involved the passage of instruments down aT-tube tract with blind grasping of the stones. The introduction of ERCP and papillotomy by Classen and Demling in 1974 resulted in an important advance for the management of common bile duct stones,lO permitting the removal of as many as 90% of such stones. 11 In patients with access to the common bile duct via a T-tube tract, flexible choledochoscopy with basket extraction is an excellent alternative. 5, 6, 24, 27 However, with both tech-
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niques, there is a failure rate secondary to too large a stone. In this situation, fragmentation is needed to aid stone removal. Mechanical lithotripsy with a strong basket is a cumbersome and traumatic method that at times fails because of breaking of the basket or nonfragmentation. Electrohydraulic lithotripsy used through a flexible instrument, with the smallest probes being 1.9 Fr and the larger probes 3 Fr, is effective. There is an incidence of duct injury if the probe is inadvertently discharged on the wall of the duct. We showed in the porcine model that perforation of the common bile duct can occur with as few as three pulses if the probe is in direct contact with the tissue surface. 7 This incidence of duct perforation may be reduced by the introduction of a shielded electrohydraulic lithotripsy probe, which has proved to be safer in the animal model.4 Two of the advantages of laser-induced shock wave lithotripsy are the small quartz fibers (200-320 ....m) that can be passed through the instrument channels of small endoscopes and its comparative safety. The advantages of small fibers, safety, and an instrument that can be used in the urinary as well as the biliary system make this an attractive technology despite its greater cost in comparison with other forms of lithotripsy. Despite a considerable volume of experimental work on biliary lithotripsy, its use clinically is limited and in an early stage of development. The first clinical report of laser lithotripsy was in 1981 by Orii et aI, who used a continuous-wave Nd:YAG laser in conjunction with T-tube choledochoscopy successfully in two patients with retained common bile duct stones. 32 As noted previously, those authors later reported the complication-free use of the same laser in 11 patients with intrahepatic and common duct stones. 33 Chen and Jan described the use of a continuous-wave Nd:YAG laser in the treatment of common duct stones using a T-tube tract and a transhepatic route in two patients. The only complication was a complaint of a burning sensation by both patients. 9 Inui et al used the continuous-wave Nd:YAG laser to treat 11 patients with symptomatic gallbladder stones by a percutaneous transhepatic route using a flexible choledochoscope. 26 The first successful endoscopic retrograde endoscopic laser lithotripsy of a common duct stone was reported in 1986 by Lux et aI, who used a pulsed Nd:YAG laser, a much safer instrument because of the lower heat production. 28 In a further report, the same group described nine patients with common duct stones treated with the flashlamppulsed Nd:YAG laser.16 Stones were broken up and the fragments extracted by basket in six patients; however, in two patients, the fragments could not be extracted, and in one patient, the stone could not be fragmented at all; these three patients underwent an operation to complete their treatment. Fragmentation was performed under fluoroscopy following endoscopic retrograde papillotomy, with the laser fiber being controlled and placed in contact with the stone by one of two methods. In one method, the stone was trapped in a laser basket and the fiber passed down the center of the basket, keeping it away from the duct wall; in the other method, a laser catheter with a balloon
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on the end was used to keep the fiber away from the wall and in contact with the stone. The "mother and daughter" retrograde endoscopic system was used in one patient to place the fiber on the stone under direct vision. Wenk and coworkers treated symptomatic gallbladder stones via a transhepatic route, using a pulsed Nd:YAG laser followed by basket and suction removal of the fragmentsY There are several disadvantages of the pulsed Nd:YAG system: the mechanism of action is the conversion of light energy into heat, which raises the issue of heat perforation of the common bile duct; and fragmentation results in the production of relatively large pieces that then have to be basket extracted. 16 For satisfactory clinical application, a more effective system is required, one that will fragment stones into small particles that are more likely to pass through the sphincter of Oddi, reducing the need for basket extraction. Although the Q-switched Nd:YAG laser has been used successfully and safely in S6 patients with renal and ureteral stones,I2 its use clinically in the biliary tree is not yet accepted. The largest experience in the literature has been generated using a S04-nm coumarin flashlamp-pumped pulsed-dye laser, of which there are two systems approved by the Food and Drug Administration for use in the United States: the Pulsolith (Technomed International, Danvers, Massachusetts) and the MDL 2000 (Candela Corporation, Wayland, Massachusetts). Cotton and Kozarek reported in 1988 the use of a coumarin dye laser emitting at S04 nm to treat seven patients using a peroral route with a "mother and daughter" endoscopic system to fragment common duct stones. 12 Using 30 to 60 mJ of energy passed through a 2S0-fLm quartz fiber, they were able to fragment stones in all patients with 20 to 2029 pulses. However, they were able to clear the duct in only four patients. Feldman and associates reported the use of the coumarin pulsed-dye laser to fragment a 2-cm intrahepatic stone via a percutaneous tract after a partial left hepatectomy. IS Using a fluoroscopically guided basket, through the center of which a 2S0-fLm quartz fiber could be passed, the stone was secured and fragmented with 60 mJ of energy using SOO pulses. The fragments were irrigated down the left hepatic duct. However, on a cholangiogram the next day, three small fragments were seen. These were basket extracted, with the majority of the other fragments being washed through the sphincter of Oddi into the duodenum. Berci et al report the treatment of a patient with a retained stone in the left hepatic duct using a coumarin pulseddye laser. 1 The stone was 4 to S mm in diameter and was found on a postoperative T-tube cholangiogram. The stone was treated with laser lithotripsy under direct vision using a flexible endoscope passed through the T-tube tract. Flowers and associates report a case of a patient with a 2.S-cm stone in the right hepatic duct that was approached by a transhepatic route. 19 The stone was fragmented with the coumarin dye laser. However, the procedure was terminated because of its length before complete fragmentation had been achieved. One week later, the biliary tract was cleared completely using ultrasonic lithotripsy, which is faster
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at fragmenting stones than the coumarin dye laser. The size and number of stones can be a problem with coumarin pulsed-dye laser lithotripsy, as it produces small fragments rather than the bigger fragments that result with other techniques. This means that fragmentation of a large stone volume, be it a single large stone or multiple smaller stones, may take a long time. Cotton and coworkers report 25 complex instances of common duct stones that either were large or would not respond to other forms of nonoperative management. 13 Five patients were treated under direct vision with the laser fiber passed through a flexible choledochoscope at the time of T-tube tract choledochoscopy, and one patient was treated through the T-tube tract using a basket with a central lumen for the laser fiber. The other 19 patients were treated with retrograde endoscopy through the papilla of Vater after a sphincterotomy, using the "mother and daughter" endoscopic system in 12 patients and, in 7 patients, under fluoroscopy using either a balloon or a laser basket system. All patients were treated using a 200-J,Lm fiber and a pulse energy of 60 mJ at 5 to 10 Hz until complete stone fragmentation or a maximum of 3500 pulses. In only 24 patients could the stone be targeted accurately and, therefore, treated. Of these, fragmentation occurred in 23 patients. Ducts were cleared subsequently in 20 patients, with only one endoscopy session being required in 12 patients. There were no major complications and one minor complication, transient bleeding through the papillotomy, which stopped spontaneously. In the five failures, other treatment plans were required. In another large series, reported by Ponchon and associates, 25 patients with bile duct stones who had failed basket extraction and mechanical lithotripsy were treated with the coumarin pulsed-dye laser.34 After undergoing a preliminary endoscopic sphincterotomy, all patients were treated via a variety of access routes: aT-tube tract in seven patients, with four of these having stones in the common duct and three in the intrahepatic ducts; a retrograde endoscopic route using either a basket or a balloon for laser fiber placement under fluoroscopy in 14 patients; and a transhepatic percutaneous route in four patients. In the seven patients treated via aT-tube tract, the stones were broken up with laser energy into at least two fragments of similar size, which were then either irrigated or pushed through the sphincterotomy site; duct clearance was achieved in all patients. The other patients were treated by retrograde endoscopy unless the stones were intrahepatic. A basket with a central lumen for a laser fiber was used in five patients, and a balloon catheter to keep the fiber tip away from the common duct wall was used in nine patients. The procedure was successful only at clearing the common duct in five patients and, of the nine patients in whom the treatment failed, two underwent operation, one received extracorporal shock wave lithotripsy, and the remaining six were treated successfully with a percutaneous transhepatic technique. In four patients with intrahepatic stones, a percutaneous transhepatic route was chosen as the primary method of delivering laser lithotripsy. In these patients, a 15-Fr transhepatic tract was developed over a 3-week period
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through which a lS-Fr choledochoscope was passed to deliver the laser lithotripsy. In the latter few patients, the tract was dilated at the initial session and a 12-Fr sheath passed, through which a 10.S-Fr endoscope was inserted. In all patients treated by the transhepatic approach, the biliary tree was cleared completely of stones. There were no reported complications of laser lithotripsy with any of the approaches. However, there were three septic episodes related to biliary endoscopy. Ponchon et al point out that the positioning of the fiber against the stone is of critical importance and think that the failure rate of the fluoroscopically directed laser lithotripsy was attributable to the difficulty in establishing a good contact between the fiber and the stone. They feel that positioning is best done endoscopically.34 We have performed laser lithotripsy using a S04-nm coumarin pulsed-dye laser, the Pulsolith, for the fragmentation of gallstones using a variety of percutaneous approaches to the biliary tract. We treated eight patients with T-tube tract choledochoscopy who had been found on postoperative T-tube cholangiography to have retained bile duct stones. Five patients had extrahepatic stones, two had intrahepatic stones, and one patient had both (Fig. 1). Laser lithotripsy was delivered by a 320-j.Lm quartz fiber passed through a 4.9-mm flexible choledochoscope using pulse energies of 100 to 120 mJ at 3 to 5 Hz. All stones were fragmented with between 207 and 2718 pulses. The resulting fragments were small enough to be washed through the sphincter of Oddi into the duodenum, with no fragments having to be removed by basket extraction; no patient had had a prior sphincterotomy. In four of five poor-risk patients, we used laser lithotripsy delivered endoscopically by a transhepatic approach to clear the biliary tree of stones. In two of the patients, a chronic transhepatic tract established over a 3-week period was used to pass a 3.S-mm flexible endoscope (Olympus Corporation, New Hyde Park, New York), and in the other three patients, an acute tract was used. Pulse energies of 100 to 140 mJ at 3 to 5 Hz were delivered in 809 to 4800 pulses. The failure was in a patient who had a fatal myocardial infarction after partial clearance at the first endoscopic treatment session and just prior to a second scheduled treatment. The myocardial infarction was thought to be unrelated to the laser lithotripsy. Three of the four patients treated successfully required two sessions to clear the biliary tree completely of stones. One patient who had had a cholecystostomy and stone removal performed operatively for acute cholecystitis was referred with a stone in a long cystic duct. Transcholecystic endoscopy of the cystic duct was performed using an 8.3-Fr flexible ureteroscope, the ACMI AUR8 (Circon/ACMI, Inc., Stamford, Connecticut), and under direct vision, the stone was fragmented completely and the fragments washed into the cystic duct using pulse energies of 110 mJ at 3 Hz for 170 pulses (Fig. 2). In two patients with gallbladder stones after the placement of a cholecystostomy tube for acute cholecystitis, we used the coumarin pulsed-dye laser through a 4.9-mm flexible choledochoscope (Olympus
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Figure 1. A patient with a stone in a branch of the right hepatic duct who was treated successfully with laser lithotripsy.
Corporation) and fragmented a large stone in one patient with basket extraction of the fragments. However, in the other patient, because of the slow rate of laser fragmentation of a large stone, treatment was completed with the ultrasonic lithotripter. Laparoscopic cholecystectomy is fast becoming an acceptable method for treating symptomatic biliary stones. However, it will not be accepted universally until the common duct can be cleared of stones at the time of laparoscopic cholecystectomy, thus avoiding the too common endoscopic retrograde papillotomy. We have used cystic duct choledochoscopy at the time of laparoscopic cholecystectomy to clear the common bile duct of a stone seen on intraoperative cholangiography. This was achieved by passing a 320-mm quartz fiber attached to
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Figure 2. A patient treated with laser lithotripsy for a small stone remaining in the cystic duct after operative cholecystostomy.
a 504-nm coumarin pulsed-dye laser through the instrument channel of an AUR8 ureteroscope to perform lithotripsy (Fig. 3). Laser lithotripsy is slower than other lithotripsy techniques for fragmenting biliary stones, particularly large stones. It is not the ideal management technique for gallbladder stones, as these stones tend to be larger and the cholecystostomy tracts usually large and straight, making the faster ultrasonic lithotripsy the method of choice. Laser lithotripsy is the method of choice for bile duct stones that cannot be extracted easily with a basket because it breaks stones into small fragments that will pass spontaneously, it is safe, the fibers are small and flexible, and it can be used under direct vision through small endoscopes. It is a technology that significantly enhances minimalaccess biliary procedures.
SUMMARY
Laser lithotripsy is an excellent method of fragmenting those biliary stones that cannot be removed easily by less technically advanced methods such as basket extraction. The energy can be delivered through fine flexible fibers, around 200 to 320 f.Lm in diameter, that can be
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Figure 3. An obese patient who had failure of two endoscopic retrograde papiliotomies prior to laparoscopic cholecystectomy and who underwent successful cystic duct choledochoscopyand laser lithotripsy at the time of laparoscopic cholecystectomy.
passed through the channels of a variety of small endoscopes. Currently, the optimal laser seems to a pulsed system because of the conversion of light to acoustic energy with minimal heating of the surrounding tissues, thus avoiding the chance of tissue injury and perforation. The best wavelength seems to be 504 nm, because at this wavelength, there is maximum absorption of laser energy by pigment stones, resulting in fragmentation using low-energy pulses. With further research, optimal wavelengths and pulse durations may emerge. References 1. Berd G, Hamlin JA, Grundfest W, et al: Percutaneous endoscopic laser lithotripsy of
retained stones in the left hepatic duct. Surg Endosc 4:36-38, 1990 2. Bergdahl L, Holmlund DEW: Retained common duct stones. Acta Chir Scand 142:145149, 1976 3. Bhcitta KM, Nishioka NS: Effect of pulse duration on microsecond-domain laser lithotripsy. Lasers Surg Med 9:454-457, 1989 4. Bhatta KM, Rosen 01, Flotte TJ, et al: Effect of shielded or unshielded laser and electrohydraulic lithotripsy on rabbit bladder. J Uroll43:857-860, 1990 5. Birkett DH, Williams LF Jr: Choledochoscopic removal of retained common duct stones via the T-tube tract. Am J Surg 139:531-534, 1980
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Address reprint requests to Desmond H. Birkett, MD, FACS Division of Surgery University Hospital 88 East Newton Street Boston, MA 02118
