Extracorporeal Shock Wave Lithotripsy for Retained Bile Duct Stones

678 Gut 1997; 40: 678-682

Fluoroscopically guided laser lithotripsy versus extracorporeal shock wave lithotripsy for retained

bile duct stones: a prospective randomised study Gut: first published as 10.1136/gut.40.5.678 on 1 May 1997. Downloaded from

R Jakobs, H E Adamek, M Maier, M Kromer, C Benz, W R Martin, J F Riemann

Abstract of stones mechanical lithotripsy is the first line Background and aims-To compare ex- treatment with a therapeutic success of about tracorporeal shock wave lithotripsy 80% to 97% and the best reported cost (ESWL) and laser induced shock wave effectiveness. This method fails in a few lithotripsy (LISL) of retained bile duct patients because the calculi are too large, stones to stone free rate, number of impacted, or located above a biliary stricture.5 therapeutic sessions, and costs. Biliary stones are resistant to the above Patients-Thirty four patients were ran- methods in only 2% to 5% of patients. For domly assigned to either ESWL or LISL this selected group extracorporeal and various therapy. The main reasons for failure of intracorporeal lithotripsy procedures were standard endoscopy were due to stone developed over the past decade."5 Laser impaction (n=12), biliary stricture (n=8), lithotripsy is the latest development in the field or large stone diameter (n=14). of fragmentation techniques. A major problem Methods-An extracorporeal piezoelec- in using this device is the requirement of tric lithotripter with ultrasonic guidance cholangioscopic guidance, which is expensive and a rhodamine 6G laser with an in- due to the cost of the cumbersome endoscopic tegrated stone tissue detection system equipment and the need for two experienced were used. LISL was performed exclus- endoscopists operating the "mother and baby" ively under radiological control. endoscope.9 The most promising laser litho- Results-Using the initial methods com- tripter has an integrated stone tissue detection plete stone fragmentation was achieved in system,10 which can be used under sole flu- nine of 17 patients (52.4%) of the ESWL oroscopic guidance and thereby should reduce http://gut.bmj.com/ group and in 14 of 17 patients (82-4%) in the expense of this means of fragmentation. the LISL group, or combined with ad- The aim of our prospective trial was to ditional fragmentation techniques 31 of compare ultrasonically guided extracorporeal the 34 patients (91 2%) were stone free at shock wave lithotripsy (ESWL) with laser the end oftreatment. In comparison LISL induced intracorporeal lithotripsy (LISL) tended to be more efficient in clearing performed under pure radiological control, the bile ducts (p=0.07, NS). Significantly chiefly with respect to stone free rates, but also on October 2, 2021 by guest. Protected copyright. less fragmentation sessions (1-29 v 2-82; the number of endoscopic sessions necessary p=0O0001) and less additional endoscopic for therapeutic success, the side effects, and sessions (0.65 v 1'6; p=0.002) were necess- costs. ary in the LISL group. There were no major complications in either procedure. Conclusions-Compared with ESWL, flu- Methods oroscopically guided LISL achieves stone Over a two year period 34 patients with com- disintegration more rapidly and with sig- plicated bile duct stones were prospectively nificantly less treatment sessions, which and randomly enrolled in the study (Table I). Department of leads to a significant reduction in cost. Inclusion criteria were as follows: (1) Medicine C, Klinikum (Gut 1997; 40: 678-682) choledochal lithiasis, diagnosed by means of Ludwigshafen, endoscopic retrograde cholangiography, (2) Academic Teaching Hospital ofthe Keywords: laser lithotripsy, extracorporeal shock wave detection of the bile duct stones by abdominal University ofMainz, lithotripsy, retained bile duct stones, endoscopic ultrasound, (3) papilla within reach of the Ludwigshafen, retrograde cholangiopancreatography. Germany R Jakobs H E Adamek TABLE I Patient's characteristics according to the two M Maier Since the introduction of endoscopic sphinc- treatment groups M Kromer terotomy in 1974,' 2 endoscopy has been C Benz ESWL LISL W R Martin widely used in the treatment of common bile J F Riemann duct stones. Particularly in elderly patients, Patients (n) 17 17 Sex 11 F 11 F Correspondence to: after previous cholecystectomy and before 6M 6M Dr RalfJakobs, laparoscopic cholecystectomy, endoscopic bile Mean age (range) (y) 72 (39-92) 72 (29-86) Department of Medicine C, Previous cholecystectomy (n(%)) 7 (41) 7 (41) Klinikum Ludwigshafen, duct clearance is preferred.3 Successful re- Symptoms on admission: Bremserstrasse 79, D-67063 moval of bile duct stones by standard endos- Painless jaundice 6 3 Ludwigshafen, Germany. Colic with or without icterus 6 8 Accepted for publication copy was achieved in 85% to 95% of patients Cholangitis 5 6 23 January 1997 in several series.4 For the remaining 5% to 15% Fluoroscopically guided laser lithotripsy versus extracorporeal shock wave lithotripsyfor retained bile duct stones 679

TABLE II Stone properties in the two treatment groups by was achieved extraction of fragments was endoscopic retrograde cholangiopancreatography radiograph attempted via endoscopic retrograde cholan- ESWL LISL giopancreatography. If sufficient fragmentation was not achievable after three ESWVL Stone diameter (mm)* 25 (8-30) 24 (12-38) Number of stones: sessions an alternative fragmentation tech- 1 6 5 nique was performed. Gut: first published as 10.1136/gut.40.5.678 on 1 May 1997. Downloaded from 2 5 3 >2 6 9 For LISL we used the Xenon flashlamp Stone position: pulsed rhodamine 6G laser with an integrated Hilum (and adjacent hepatic ducts) 4 3 Upper half of the CBD 4 6 stone tissue detection system (Lithognost, Carl Prepapillary half of the CBD 9 8 Baasel Lasertechnik, Starnberg, Germany). Concomitant bile duct structure 5 5 The stone tissue detection system, as described *Stone diameter=maximal stone diameter in case of more than elsewhere,'0 is based on the analysis ofthe back one stone. scattered laser energy. If the intensity of the CBD=Common bile duct. light is below a defined threshold level, it indicates that the glass fibre is not in contact with a bile duct stone and the laser pulse is cut endoscope, (4) failure of standard endoscopic off with the aid of a polariser preventing tissue extraction manoeuvres including endoscopic from being damaged." sphincterotomy and at least one attempt at The laser glass fibre (250 ,um or 300 pum mechanical lithotripsy, (5) the patient's in- core diameter) was inserted in a 5 Fr or 7 Fr formed consent. gauge Huibregtse or balloon catheter and Patients were excluded from the study if passed through the papilla via the working they had major coagulation problems, were channel of a standard duodenoscope (Olympus pregnant, or if one of the inclusion criteria was JF 1-T20). As the laser fibre itself is not not fulfilled. detectable by fluoroscopy the metal tipped All patients were diagnosed as having bile catheter was positioned in close proximity to duct stones by endoscopic retrograde chol- the stone and then the fibre was gently pushed angiopancreatography at our institution or at out of the catheter. Treatments were per- the referring hospital. Data regarding stone formed at an energy level of 100 to 150 mJ per size, number, and location were based on the pulse at a repetition rate of 8 to 10 Hz. During endoscopic retrograde cholangiopancreatogra- the laser treatment the fragmentation effect phy radiograph (maximum stone size was was monitored by fluoroscopy after instillation measured based on the diameter of the of contrast media into the bile duct. endoscope). Table II gives the properties ofthe LISL was limited to three treatment sessions stones. with a maximum duration of 45 minutes. After failure of at least one attempt at Laser therapy was discontinued if there was no http://gut.bmj.com/ mechanical lithotripsy a nasobiliary drain was fragmentation effect, when the stones could inserted and the patients were randomly not be correctly targeted by the laser fibre, or assigned to ESWL or LISL. The main reasons if they were not detectable by the integrated for failure of standard endoscopy were stone stone tissue detection system. impaction (n=12), biliary stricture (n=8), or In the case of failure of the initial treatment large stone diameter (n= 14). patients were switched to an alternative method

All extracorporeal and intracorporeal treat- (LISL, ESWL, or electrohydraulic lithotripsy. on October 2, 2021 by guest. Protected copyright. ment sessions were performed under intra- For electrohydraulic lithotripsy we used the venous sedation (2 to 5 mg midazolame) and Lithotron EL-23 (Walz Electronic, Rohrdorf, additional analgesia if necessary (25 to 100 mg Germany) under strict cholangioscopic control. pethidine). Patients were monitored by clinical observation and continuous pulse oximetry during the procedures. STATISTICAL ANALYSES Data were entered into a database program and statistics were calculated with a statistical METHODS software package (Unistat 3 0 for Windows; ESWL was performed with an ultrasonically Unistat Co, UK). Values are expressed as guided piezoelectric lithotripter (Piezolith median (range) or mean (SD), unless other- 2300, R Wolf, Knittlingen, Germany). Stones wise stated. A Mann-Whitney U test or two were located with the two integrated 4 MHz tailed Fisher's exact test was used for com- ultrasound scanners and the shock wave focus parison between the two groups. A p value energy was increased from a minimum of 600 <0 05 was considered to be significant. bar to the highest tolerated energy level (maximum 1200 bar). During the ESWL session the bile duct was irrigated continuously Results with saline solution through a nasobiliary ESWL GROUP drain. Bile duct concrements of all patients (17) were Patients were treated with a maximum 5000 visible by the integrated ultrasound scanner pulses per session. Fragmentation effects were before therapy. Patients were treated with a controlled by abdominal ultrasound after each mean of 2-82 (1-24) ESWL sessions cor- session. If the fragments were not properly responding to a mean number of 10000 detectable by ultrasound, fluoroscopy after (1800-19 500) shock wave pulses. To achieve instillation ofcontrast media via the nasobiliary complete duct clearance a mean of 1 6 (0-7) drainage was used. Once stone disintegration additional sessions of endoscopic retrograde 68060akobs, Adamek, Maier, Krdmer, Benz, Martin, Riemann

cholangiopancreatography were necessary. (due to the duration of the preceeding LISL Mean duration of hospital stay was 13-4 (4-8) therapy). Overall, 0-65 (0 68) additional en- days; mean interval between first ESWL and doscopic retrograde cholangiopancreatography discharge from the hospital was 6&2 (2 2) days. sessions per patient were necessary to clear the In nine of the 17 patients (53%) complete bile ducts completely.

stone fragmentation using ESWL was achieved The average hospital stay was 12-6 (7) days Gut: first published as 10.1136/gut.40.5.678 on 1 May 1997. Downloaded from and was followed by the extraction of re- in this group; the mean period between first maining fragments in one additional endos- LISL and discharge from hospital was 3-5 (3 3) copic retrograde cholangiopancreatography days. session. In three out of 17 patients stones were In three of the 17 patients LISL failed. In only partially fragmented; in five of the 17 two of them a sufficient fibre stone contact was patients (29-4%) there was no major fragmen- not achievable due to a parapapillary diver- tation effect. Finally, in eight of 17 patients ticula and an unusually dilated distal common further fragmentation techniques were re- bile duct; both patients became stone free after quired. ultrasonically guided ESWL. In one patient The reasons for failure of ESWL therapy only a partial stone fragmentation was achieved; were as follows: loss of sonographic visibility he was successfully treated by mechanical of the bile stone during the procedure (three lithotripsy. Combined with additional frag- patients), or no fragmentation (n=2), or an mentation modalities stones were removed unsatisfactory (n=3) fragmentation effect prob- successfully in all 17 patients (100%) in the ably due to the stability of the stones. LISL group. In four patients electrohydraulic lithotripsy Complications due to laser therapy were as was used. Two of those became stone free. follows: one patient had an episode of acute In three patients fluoroscopic guided LISL cholangitis, and one patient complained of was performed because of insufficient stone pain during LISL (despite intravenous fragmentation during ESWL; stones were analgesia). In three patients small amounts of removed completely in two of these patients. blood were oozing from the papilla after In the end, 14 of 17 (82.4%) patients were pushing the glass fibre out of the endoscopic stone free after ESWL alone (nine of 17) or in retrograde cholangiopancreatography catheter. combination with other methods (five of 17) in However, bleeding ceased in each patient the ESWL group. during the procedure without any inter- One of the patients with stones resistant to vention. the endoscopic fragmentation techniques was sent to the surgical department to clear her bile ducts during cholecystectomy. The remaining COMPARISON OF ESWL WITH LISL two patients (ages 92 and 81 years) were Both randomly assigned groups were compar- http://gut.bmj.com/ treated by endoprosthesis insertion because able with regard to sex, age, number, and they were poor candidates for operation due to location of the bile stones. coexisting diseases. Number of fragmentation sessions was more Some minor complications were noticed in favourable in the LISL group than the ESWL the ESWL group: one patient reported pain group (Mann-Whitney U test: p=00001). The despite intravenous sedoanalgesia; one patient number of fragmentation pulses was signifi- had a vagovasal reaction (hypotension, diz- cantly lower for laser fragmentation therapy on October 2, 2021 by guest. Protected copyright. ziness) which necessitated stopping the ESWL (p=00053). session (the patient became stone free after the Additional endoscopic retrograde cholangio- next ESWL session). One patient developed pancreatography sessions were necessary in small skin petechiae immediately after ESWL. both treatment groups, although significantly The treatment related mortality was zero in fewer in the LISL group (ESWL 1 6 v LISL the ESWL group. 0 65), the difference reaching significance by Mann-Whitney U test (p=0 002). The stone free rate according to LISL LISL GROUP therapy alone was higher than ESWL, but this The seventeen patients of the LISL group were difference was not significant (Fisher's exact treated by a mean of 1 29 (0 46) LISL sessions test, p=007). Using a combination of various and 3744 (800-21 241) correctly targeted treatment methods bile ducts were completely pulses corresponding to a total number of 5300 freed of stones in 31 of 34 patients (91 2%). (1440-22 831) laser pulses. The average stone The two groups showed almost identical detection rate (ratio ofcorrectly targeted pulses duration of hospital stay (mean 13-4 v 12-6 to the total number of pulses) was about 68% days; p=03, NS). The interval between the with a slight but not significant increase as the first treatment session and hospital discharge study period progressed. was significantly shorter for those treated by In combination with standard extraction laser first (3 5 v 6-2 days; p=00002). manoeuvres using balloon catheters or baskets An estimated cost analysis was performed 14 of the 17 (82-4%0) patients became stone based on the costs for lithotripsy sessions, the free with fluoroscopic guided LISL. Nine of additional endoscopic retrograde cholangio- these 14 patients were stone free in the same pancreatography procedures, and the charges session; in five of them one additional endos- for hospital stay. The total charge to the copic retrograde cholangiopancreatography patients in the ESWL group was £4218 and in session was necessary because the patients the LISL group it was £3343; an advantage of tolerated no further extraction manoeuvres about £875 (Table III) for laser therapy. Fluoroscopically guided laser lithotripsy versus extracorporeal shock wave lithotripsyfor retained bile duct stones 681

TABT F IlI Estimated cost effectiveness ofthe two treatments based on the hospital charges equipment is expensive with acquisition costs in 1994 ranging from about £270 000, but these sys- Costs ESWL group Costs LISL group Costs tems are available at many institutions, because Cost item (O) (mean n) (IC) (mean n) (IC) they are widely used by urologists. Data on laser lithotripsy for complicated bile ESWL 328 2 82 925 - - LISL 245 - - 129 316 duct stones has been published from several Gut: first published as 10.1136/gut.40.5.678 on 1 May 1997. Downloaded from ERCP 82 1-6* 131 0.65* 43.3 One hospital day 236 13 4 3162 12-6 2974 institutions. For the coumarin green and Nd:YAG laser, stone fragmentation rates of Total costs per patient - 4218 - 3343 about 80% to 90% were reported, mainly using ERCP=Endoscopic retrograde cholongiopancreatography. LISL under direct cholangioscopic control.1658 In this trial LISL is advantageous over ESWL with a mean benefit of about £875 per patient. ERCP after When performing LISL under fluoroscopic *Additional lithotripsy. guidance the method failed in up to 80% of patients, in general because positioning of the Discussion glass fibre on the stone was difficult.'7 Interventional endoscopy has revolutionised The main advantage of the rhodamine laser the management of bile duct stones since used in this trial was the integrated stone tissue the 1970s. But despite improved endoscopic detection system. This system allows the equipment, standard endoscopic procedures treatment to be performed under fluoroscopic (including sphincterotomy and mechanical control with excellent safety and fragmentation lithotripsy) fail in about 5% of patients.4 For success rates of up to 90%/o.1o 19 20 In this study this highly selected group of patients several fluoroscopic guided LISL with the rhodamine intracorporeal and extracorporeal fragmen- 6G laser was effective in clearing the bile ducts tation modalities have been developed.6 12 in about 80% of the patients of the LISL In the past most of the published findings group and even in two of three patients after were on the use of ESWL in the treatment of failure of ESWL, and there were only minor retained bile duct stones. Several types oflitho- complications. triptors with different methods of generating To date only two major comparative pros- the shock waves were developed. Most of pective and randomised studies dealing with the ESWL treatments were performed under intracorporeal and extracorporeal methods for radiological guidance with stone free rates fragmenting retained gall stones have been ranging from 53% to 94%.68 13 14 presented. In our study stone disintegration through In a recently published trial2' 35 patients extracorporeal measures was achieved in 12 of with complicated bile duct stones were pros- 17 patients (71%) but only nine of the 17 pectively randomised to ESWL or cholangio- patients (52A4%) became stone free after scopically controlled electrohydraulic litho- ESWL alone. The number of fragmentation tripsy. The study showed a slight but not http://gut.bmj.com/ sessions necessary for duct clearance was significant advantage for the electrohydraulic higher than reported from other study groups lithotripsy group concerning stone free rate, including our previously published data using duration of hospital stay, and hospital charges. the same lithotripter.7 In the end both groups were treated com- There are several reasons for our ESWL parably efficiently and safely, choledochos- results being less favourable in this study. The copic electrohydraulic lithotripsy being stone properties differ between the published advantageous considering the number of on October 2, 2021 by guest. Protected copyright. studies. In this trial 11 of the 17 patients treatment sessions required. treated by ESWL had two or more stones. It Neuhaus et al presented a study in 1995 in is known that the piezoelectric lithotriptor which radiologically guided ESWL was com- provides only a small focus which does not pared prospectively with laser lithotripsy.22 permit simultaneous fragmentation of more Although using the rhodamine 6G laser with than one stone.7 This problem was also the automatic stone tissue detection system reported in the use of an electrohydraulic almost all laser therapies (28 out of 30 patients) ESWL system with a small second shock wave were performed under cholangioscopic control focus. 13 and most of the patients were treated via the The loss of sonographic visualisation was percutaneous route. LISL was preferable and another major problem. Previous studies have superior to ESWL under these conditions for shown that stones in the bile duct could be the number oftreatment sessions (p

favourably less (p=0002). This is very similar 2 Kawai K, Akasaka Y, Murakami K. Endoscopic sphincterotomy of the ampulla of Vater. Gastrointest Endosc to the two previous studies mentioned above. 1974; 20: 148-51. By contrast with the study of Neuhaus et al22 3 Escourrou J, Berth&lemy P. Biliary complications after laparoscopic cholecystectomy. Dtsch Med Wochenschr in our trial laser fragmentation was performed 1993; 118: 1157-62. exclusively under fluoroscopic guidance. This 4 Classen M, Hagenmuller F, Knyrim K, Frimberger E. Giant bile duct stones - treatment.

non-surgical Endoscopy Gut: first published as 10.1136/gut.40.5.678 on 1 May 1997. Downloaded from manner of treatment was chosen due to the 1988;20:21-6. cost effeciveness of using a cholangioscopic 5 Schneider MU, Matek W, Bauer R, Domschke W. Mechanical lithotripsy of bile duct stones in 209 patients: control. In our opinion the future for intracor- effects of technical advances. Endoscopy 1988; 20: poreal laser lithotripsy is the fluoroscopically 248-53. 6 Binmoeller KF, Bruckner M, Thonke F, Soehendra N. guided approach. This reduces the costs for Treatment of difficult bile duct stones using mechanical, the endoscopic equipment (for example, the electrohydraulic and extracorporeal shock wave lithotripsy. Endoscopy 1993; 25: 201-6. babyscope) and can be performed by one 7 Adamek HE, Buttmann A, Hartmann CM, Jakobs R, experienced gastroenterologist. Riemann JF. Extracoporeal piezoelectric lithotripsy of intra- and extrahepatic biliary tract stones. Dtsch Med Cost analysis of our study was estimated, Wochenschr 1993; 118: 1053-9. comprising direct hospital charges and costs of 8 Sauerbruch T, Stern M. Fragmentation of bile duct stones by extracorporeal shock waves. Gastroenrerology7 1989; 96: endoscopy and lithotripsy. The estimation was 146-51. based on our specific local charges and did not 9 Prat F, Fritsch J, Chourv AD, Frouge C, Marteau V, Etienne JP. Laser lithotripsy of difficult biliarv stones. include the costs to society (for example, lost Gastroi?itest Endosc 1994; 40: 290-5. wages and productivity), which is reasonable as 10 Ell C, Hochberger J, May A, Fleig WE, Bauer R, Mendez L, Hahn EG. Laser lithotripsy of difficult bile most of our study patients were over 65 years duct stones by means of a rhodamine-6G laser and an old and retired. Despite a comparable total integrated automatic stone-tissue detection system. Gastrointest Endosc 1993; 39: 755-62. duration of hospital stay, laser therapy is 11 Schmeller N, Kriegmair M, Liedl B, Hofstetter A, advantageous over ESWL with a mean benefit Muschter R, Thomas S, Knipper A. Laserlithotripsie mit automatischer Abschaltung bei Gewebekontakt. Urologe A of about £875 per patient. These charges are 1990;29: 309-12. representative for our hospital and may not be 12 Classen M, Hagenmueller F. Treatment of stones in the bile duct via duodenoscopy. Endoscopy 1989; 21: 375-7. correct for other institutions and countries. 13 Ponchon T, Martin X, Barkun A, Mestat JL, Chavaillon A, In conclusion, laser lithotripsy with a stone Boustiere C. Extracorporeal lithotripsy of bile duct stones using ultrasonography for stone localization. tissue recognition system was at least as Gastroenterology 1990; 98: 726-32. efficient as ESWL in fragmenting retained bile 14 Sauerbruch T, Holl J, Sackmann M, Paumgartner G. Fragmentation of bile duct stones by extracorporeal shock duct stones with a tendency towards a higher wave lithotripsy: a five-year experience. Hepatology 1992; stone free rate (p=007). When performing 15: 208-14. 15 Wermke W. Sonographic diagnosis of concrements of the laser therapy as a first line method, significantly bile ducts. Ultraschall Med 1992; 13: 246-54. less fragmentation sessions and additional 16 Nishioka NS, Levins PC, Murray SC, Parrish JA, Anderson RR. Fragmentation of biliary calculi with endoscopic retrograde cholangiopancreatog- tunable dye lasers. Gastroenterology 1987; 93: 250-5. raphy sessions were necessary to achieve 17 Cotton PB, Kozarek RA, Schapiro RH, Nishioka NS,

Kelsey PB, Ball TJ, et al. Endoscopic laser lithotripsy of http://gut.bmj.com/ complete bile duct clearance. The lower large bile duct stones. Gastroewiterologjx 1990; 99: number of therapeutic interventions resulted in 1128-33. 18 Kozarek RA, Low DE, Ball TJ. Tunable dye laser a better cost effectiveness for LISL. As stated, lithotripsy: in vitro studies and in vivo treatment of complete duct clearance can be reached more choledocholithiasis. Gastroiwest Endosc 1988; 34: 418-22. rapidly and less expensively by fluoroscopic 19 Neuhaus H, Hoffmann W, Gottlieb K, Classen M. guided LISL than by ESWL under sono- Endoscopic lithotripsy of bile duct stones using a new laser with automatic stone recognition. Gastromitest Endclosc graphic guidance and LISL should be con- 1994;40:708-15. sidered as the first line treatment for retained 20 Jakobs R, Maier M, Kohler B, Riemann JF. Peroral laser on October 2, 2021 by guest. Protected copyright. lithotripsy of difficult intrahepatic and extrahepatic bile bile duct stones. duct stones. Laser effectiveness using an automatic stone- tissue discrimination system. A i7 Gastroewerol 1996; 91: This work was presented in part at the 96th Annual Meeting 468-73. of the American Gastroenterological Association/Digestive 21 Adamek HE, Buttmann A, Wessbecher R, Kohler B, Disease Week, San Francisco, California, 1996. We are grateful Riemann JF. Clinical comparison of extracorporeal to Miss Eibhlin Ni Choileain for her help in preparing this piezoelectric lithotripsy (EPL) and intracorporeal manuscript. electrohydraulic lithotripsy (EHL) in difficult bile duct stones. Dig Dis Sci 1995; 40: 1185-92. 22 Neuhaus H, Zillinger C, Born P, Ott R, Allescher H, Rosch T, Classen M. Randomized study of endoscopic 1 Classen M, Demling L. Endoskopische Sphinkterotomie laserlithotripsy (ELL) v extracorporeal shock-wave der Papilla Vateri und Steinextraktion aus dem D. lithotripsy (ESWL) for difficult bile duct stones. choledochus. Dtsch Med Wochenschr 1974; 99: 496-7. Eiidoscopy 1995; 27: S48(A).