Choledochoscopic Electrohydraulic Lithotripsy andLithotomy for Stones in the Common Bile Duct,Intrahepatic Ducts, and Gallbladder

HIDEO YOSHIMOTO, M.D., SEIYO IKEDA, M.D., MASAO TANAKA, M.D., SHINJI MATSUMOTO, M.D.,and YUJI KURODA, M.D.

Choledochoscopic lithotomy with the aid of electrohydrauliclithotripsy was performed in 40 patients, including 16 patientswith choledocholithiasis, 15 with hepatolithiasis, and 9 withcholecystolithiasis. As a route for the choledochoscopy, a T-tubetract, external cholecystostomy, or jejunal limb of hepaticoje-junostomy was used in nine patients, while percutaneous trans-hepatic biliary drainage followed by dilatation of the track wasestablished in 31 patients. The largest cholesterol stone measured55 mm by 33 mm and the largest bilirubinate stone measured52 mm by 37 mm. The stones were disintegrated in all but onepatient in whom choledochoscopic access to a gallstone was dif-ficult due to deformity of the gallbladder. Complete removal ofthe stones was achieved in 38 of 39 patients. In a patient withhepatolithiasis, small stones located deep in inaccessiblebranches of the intrahepatic duct remained unremovable. Therewere no serious complications. Minor complications occurred,including bleeding from the bile duct mucosa in four patientsand postprocedure chills and fever in three. Choledochoscopiclithotomy with electrohydraulic lithotripsy is efficient and usefulto remove biliary calculi in patients who are poor surgical risks.

A VARIETY OF NONSURGICAL approaches for thetreatment of cholelithiasis are available. Endo-scopic sphincterotomy (EST)"2 and choledo-

choscopic lithotomy3l4 have gained wide acceptance.However huge stones and impacted stones continue topresent a technical problem. Chemical dissolution5'6 andfragmentation of gallstones using extracorporeal shockwave7 are receiving enthusiastic trials but are not alwayssuccessful.

Previously we reported the use of electrohydrauliclithotripsy (EHL) under direct visual control during cho-ledochoscopy to remove intrahepatic stones.8 This report

Correspondences and reprint requests: Hideo Yoshimoto, M.D., De-partment of Surgery I, Fukuoka University School of Medicine, 7-45-1,Nanakuma, Fukuoka 814-01, Japan.

This study was supported in part by the clinical research fund fromthe Fukuoka University Hospital and the Japanese Foundation for Re-search and Promotion of Endoscopy.

Accepted for publication: January 19, 1989.

From the Departments of Surgery I, Fukuoka UniversitySchool of Medicine, and Kyushu University Faculty of

Medicine, Fukuoka, Japan

addresses the results of application of the EHL techniquein a new series of 40 patients. The present series includespatients with calculi in the common bile duct, gallbladder,and the intrahepatic ducts.

Materials and Methods

Patients

From June 1985 to June 1988, choledochoscopic elec-trohydraulic lithotripsy and lithotomy were performed in40 patients with stones in the common bile duct, intra-hepatic ducts, or gallbladder (Table 1). The series included16 men and 24 women, ranging in age from 45 to 87years. Eleven patients were between 70 and 80 years ofage and seven patients were older than 80 years. All thesepatients had one or more reasons that rendered nonsur-gical removal of the stones preferable (Table 1).The size of the stone (stones) measured on direct chol-

angiograms was greater than 30 mm in diameter in 9patients, between 20 mm and 30 mm in 10 patients, andbetween 7 mm to 20 mm in the remaining 21 patients.The stone was impacted at the distal common bile ductin 12 patients. Twenty-three patients had less than 4stones, 6 patients had 5 to 10 stones, and 11 patients hadnumerous stones. Eleven patients had cholesterol stones,the largest of which measured 55 mm by 30 mm, whilethe other 29 patients had pigment stones, the largest ofwhich measured 52 mm by 37 mm. Computed tomog-raphy performed in one half of these patients revealeddistinct calcification of the stones in seven patients.Common bile duct stones. Eight of 16 patients with

common bile duct stones were high surgical risks; 4 pa-tients were older than 80 years, 3 had a history ofmultiple

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CHOLEDOCHOSCOPIC ELECTROHYDRAULIC LITHOTRIPSY 577TABLE 1. Indications of Choledochoscopic

Electrohydraulic Lithotripsy

Numberof

Indications Remarks Patients

Choledocholithiasis Residual stones with a 5biliary tube in place

Extraction failed after EST* 5Difficult duodenoscopic 6

approach

Hepatolithiasis Polysurgery 4Biliary cirrhosis 4Retained stones 3Advanced age (over 77 years) 2Previous operation for I

gallbladder cancerDetected by chance without Isymptoms

Cholecystolithiasis Advanced age 4Polysurgery 2Chronic renal failure ICongestive heart failure ISchizophrenia I

Total 40

* EST, endoscopic sphincterotomy.

abdominal operations, 1 had spinal cord injury, and 1had ischemic heart disease. Twelve of these patients hadundergone cholecystectomy previously, while 4 patientshad gallbladders with (1 patient) or without (3 patients)gallstones.

Five of the 16 patients had a T-tube (4 patients) or apercutaneous transhepatic biliary drainage (PTBD) tube(1 patient) in place. Five patients had had EST performedbut duodenoscopic extraction had failed because thestones were huge (larger than 30 mm) in 3 patients, im-pacted and immobile in 1, or located beyond a bile ductstenosis due to chronic pancreatitis in 1 patient. The duo-denoscopic approach was considered inadequate for var-ious reasons in the other six patients. Two of these hadthe anomalous union of the pancreatic and bile ducts.One had undergone Billroth II gastrectomy. The stonewas impacted at the distal common bile duct in one. Thepapilla was situated within a diverticulum in one. A hugestone (55 by 30 mm) occupied the entire lumen of thebile duct in another patient.

Intrahepatic stones. Fifteen patients had stones in theintrahepatic ducts. All but one patients with intrahepaticstones had a history of one or more biliary operations.Fourteen of the 15 patients had a reason for the nonop-erative approach for removal of the intrahepatic stones(Table 1). An asymptomatic patient in whom the intra-hepatic stones were detected by echography refused sur-gical treatment.

Fourteen of these 15 patients were considered to haveprimary hepatolithiasis, which was associated with com-

mon bile duct stones in four patients. Another patienthad hepatolithiasis secondary to stenosis of the commonhepatic duct injured at cholecystectomy 15 years before.In two patients, the intrahepatic stones were first discov-ered by T-tube cholangiography. Four patients had un-dergone EST for removal of common bile duct stonesand one patient had transduodenal sphincteroplasty, butthe intrahepatic stones were retained.

Gallbladder stones. Nine patients had stones in thegallbladder. Two of them presented with jaundice andcholangitis due to a so-called confluence stone and hadPTBD performed (Fig. 1). Two other patients had an ex-ternal cholecystostomy for acute cholecystitis; one ofthemhad undergone transhepatic drainage of a liver abscesssecondary to cholecystitis. The remaining five patientshad percutaneous transhepatic gallbladder drainage(PTGBD) to provide a route for lithotomy. All of thesenine patients were poor operative risks (Table 1).

Instruments

An electric surge current generator (Lithotron EL-2 1,Walz Elektronik Gmbh, Rohrdorf, West Germany) witha 4.5 French size lithotripsy probe was used. The intensityof discharge was usually set at 2 with a frequency of 20per second. When the stone was hard, the intensity wasincreased to 3.A small-caliber choledochofiberscope (4.8 mm, model

CHF Pl 0, Olympus Optical Co., Tokyo, Japan) was usu-ally used. In cases in which the stones were larger than25 mm in diameter, a choledochoscope with a larger di-ameter (6.5 mm, model CHF B3, Olympus Optical Co.,Tokyo, Japan) was used, because more rapid infusion ofsaline through its larger biopsy channel permitted us tokeep the endoscopic view clear during the procedure.

Routesfor Choledochoscopy

Table 2 shows the routes for insertion of the choledo-choscope and lithotripsy instruments. A PTBD tract wasused after dilatation in 26 patients, a T-tube tract in 6, aPTGBD tract in 5, and an external cholecystostomy tractin 2 patients. In another patient, a blind end ofthe jejunallimb subcutaneously implanted at previous Roux-en-Yhepaticojejunostomy was reopened and used as a routefor choledochoscopy.

Techniques

To establish the percutaneous transhepatic route, theintrahepatic duct or gallbladder was entered under ultra-sonic guidance. Using a guide wire technique, a 7.2 Frenchbiliary drainage catheter for PTBD or a 10 French Malecotcatheter for PTGBD (Cook, Inc., Markham, Ontario,Canada) was placed in the common bile duct or gallblad-der, respectively. The catheter tract was dilated twice a

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YOSHIMOTO AND OTHERS Ann. Surg. * November 1989

FIGS. lA-C. Cholangiograms in a 84-year-old woman with a huge con-

fluence stone. The patient also had diabetes mellitus and cirrhosis of theliver. (A) Percutaneous transhepatic biliarv drainage under ultrasoundguidance was performed to relieve cholangitis. A stone, about 40 mmin diameter, occluding the confluence of the cvstic duct and commonbile duct. was visualized. (B) After dilatation of the sinus tract. a cho-ledochoscope was introduced into the bile duct and an electrohydrauliclithotripsy probe was advanced through the catheter channel. The probewas approximated closely to the stone under direct visual control. (C)The stone was broken into several fragments after application of dischargesparks.

week by replacing the catheter with a larger one by 2French size. A 16 to 20 French (5.3 to 6.7 mm) sinustract was obtained within 2 weeks.

Choledochoscopy was first attempted 3 weeks afteroperative or percutaneous biliary catheterization. Thedrainage catheter was removed, leaving a guide wire in

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CHOLEDOCHOSCOPIC ELECTROHYDRAULIC LITHOTRIPSY

TABLE 2. Routes for Choledochoscopic Electrohydraulic Lithotripsy

Numberof

Indications Routes Patients

Intrahepatic stones PTBD tract* 13T-tube tract 3

Common duct stones PTBD tract 11T-tube tract 3Jejunal limb of 1

hepaticojejunostomy

Gallbladder stones PTGBD tractt 5External cholecystostomy 2PTBD tract 2

* PTBD, percutaneous transhepatic biliary drainage.t PTGBD, percutaneous transhepatic gallbladder drainage.

the biliary tract. The choledochoscope was then intro-duced into the biliary tract over the guide wire placed inthe catheter channel. When the sinus tract proved im-mature, further attempts for lithotomy were postponedfor 1 week. Once maturation of the track was confirmed,the biliary tract was entered under direct visual controlwithout the aid of the guide wire. After a gallstone wasvisualized, the lithotripsy probe was passed through thecatheter channel, the tip was kept in the close proximityof the stone, and the discharge sparks were applied to thestone under direct vision. After the stone was disinte-grated, a large fragment of the stone was grasped in abasket catheter and pulled out along with the choledo-choscope through the sinus tract. This procedure was re-peated to remove as many large fragments as possible.Small fragments were removed by irrigation and suctionthrough the choledochoscope. The lithotripsy was per-formed once or twice a week, each session being limitedto one hour.

Results

In all but one of the 40 patients the stones were dis-integrated into sludge or fragments measuring 5 mm orless in diameter, yielding the overall success rate of 97%(Table 3). We were unable to fragment a stone impactedin the cystic duct in only one patient because it was un-reachable by choledochoscopy. Fragmented stones werecompletely removed in 38 patients using the combinedtechnique of basket extraction, irrigation, and suction. Inonly one patient with hepatolithiasis, stones remained inthe small branches of the right posterior segmental ductbecause this area was difficult to approach through thePTBD tract established from the left lateral segmentalduct (Fig. 2).

Most cases required multiple sessions of chledochos-copic lithotripsy and lithotomy. The number of sessionsper patient was 4.5 ± 2.5 (mean ± SD), ranging from twoto ten. The length from the first biliary catheterizationuntil completion of lithotomy was 40 ± 12 days. These

579

figures differed among three groups ofpatients, the small-est figures were in patients with common bile duct stonesand largest were in patients with intrahepatic stones (Ta-ble 4).

In three of nine patients with gallbladder stones thefragments moved from the gallbladder to the commonbile duct. The fragments further passed spontaneously intothe duodenum in one patient within 1 week, but the frag-ments remained in the common bile duct for 2 weeks intwo other patients, necessitating EST for removal of thefragments (Fig. 3). In one of the remaining six patients,the fragments stayed in the cystic duct. Because tortuosityof the cystic duct prohibited basket extraction of thesefragments, irrigation with 500 mL of saline through thePTGBD catheter was used for five days after EST, resultingin clearance of the fragments.A firm sinus track formed within 3 weeks in 38 patients.

Maturation ofthe track took 2 months in one ofthe othertwo patients because of hepatic congestion secondary tochronic heart failure, and 1.5 months in the other patient,in whom a silicon catheter of the Malecot type was usedfor maintenance of the sinus track because deep cannu-lation into the intrahepatic duct was prevented by thestones occupying the whole lumen.The procedure was well tolerated by all the patients

and caused no serious adverse effects. Minor bleeding fromthe mucosa of the bile duct occurred in four patients. Inthree of them, bleeding caused by scratching of the bileduct wall with the tip of the lithotripsy probe stoppedspontaneously. Bleeding in another patient occurred whena stone packed in the left hepatic duct was fragmented bythe right intercostal approach. The bleeding was controlledby compression with an 18 French catheter advanced intothat duct over the guidewire under fluoroscopic control.Three patients had transient chills and fever after the pro-cedure; this was probably due to cholangiovenous refluxcaused by increased biliary pressure during saline infusioninto the bile duct.

During the application of spark discharge the endo-scopic view was often blurred by dispersion of small frag-ments and bubbles, particularly when the small-calibercholedochoscope (CHF PO0) was used because the catheterchannel was filled with the 4.5 French probe, which pre-vented irrigation with saline. This kind of difficulty wasminimal when the larger choledochoscope (CHF B3) wasused because of the larger catheter channel; however, the

TABLE 3. Results of Choledochoscopic Electrohydraulic Lithotripsy

Results/Complications Number of Patients

Successful fragmentation 39 (97%)Complete removal 38 (95%)Incomplete removal IIntrabiliary bleeding 4Chills and fever 3

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YOSHIMOTO AND OTHERS

FIGS. 2A-C. Cholangiograms in a 58-year-old woman withstones in the left intrahepatic duct and common bile duct. Thepatient had undergone cholecystectomy with common duct ex-

ploration and endoscopic sphincterotomy 26 and 8 years pre-

viously. respectively. (A) A huge stone. 51 mm by 42 mm. whichfilled the left lateral segmental duct, was visualized by chole-dochoscopy through the PTBD tract. Several stones were presentin the common bile duct. The right posterior segmental ductwas not visualized on this occasion. (B) The intrahepatic stonewas fragmented into numerous small pieces by choledochoscopicelectrohvdraulic lithotripsy. (C) After removal of the stones fromthe left hepatic duct and common bile duct bv choledochoscopiclithotomy. cholangiographv using a balloon catheter revealedsmall stones in the branches of the right posterior segmentalduct (arrow). In spite of several attempts through the PTBDtract at the left lateral segmental duct. this area was inaccessibleby choledochoscopy. resulting in incomplete lithotomy.

sinus track had to be dilated up to 18 French, requiringseveral more days before choledochoscopy was attempted.The objective lens at the tip of the choledochoscope

TABLE 4. Number ofCholedochoscopic Sessions and Lengthfrom Biliary Catheterization to

Completion ofLithotomy

Biliary CatheterizationNumber of to Completion of

Indications Sessions* Lithotomy (Days)*

Common duct stones 3.2 ± 1.2 28 ± 6Gallbladder stones 5.2 ± 2.9 42 ± 14Intrahepatic stones 6.0 ± 2.6 50 ± 12

Overall 4.5 ± 2.5 40 ± 12

* Mean ± SD.

was damaged by the shock wave in one of the 51 sessionsof lithotripsy. The damage occurred when a large stoneimpacted in the left hepatic duct was fragmented throughthe right intercostal approach. It was extremely difficultto keep a sufficient distance between the tip of the cho-ledochoscope and the stone.

Twenty-seven patients (choledocholithiasis, 12; cho-lecystolithiasis, 9; hepatolithiasis, 6) more than 1 year aftercholedochoscopic lithotripsy were followed by telephoneinterview. The follow-up period was up to 36 months witha mean of 20.8 ± 8.9 months. Twenty-four of these pa-tients were asymptomatic and two patients were dead.The two death were not related to the lithotripsy proce-dure. One ofthe two patients who had hepatolithiasis andbiliary cirrhosis secondary to bile duct injury at a previousoperation died of hepatic coma and gastrointestinal

580 Ann. Surg. * November 1989

CHOLEDOCHOSCOPIC ELECTROHYDRAULIC LITHOTRIPSY 581

FIGS. 3A-D. Cholangiograms in a 72-year-old man with large gallstones and chronicrenal failure. (A) Percutaneous transhe-patic cholecystography showed two stones,30 mm in diameter, in the gallbladder.(B) The lithotripsy probe was in place. (C)The stones were disintegrated into pieces.(D) Some fragments moved into the com-mon bile duct after the lithotripsy, neces-sitating endoscopic sphincterotomy andbasket extraction.

bleeding 7 months after lithotripsy and lithotomy. Theother patient with obsolete myocardial infarction died ofanother attack of myocardial infarction 4 months afterlithotripsy. Only one of the 27 patients was symptomaticat the follow-up interview. This patient had lithotripsyfor the treatment of choledocholithiasis. Computed to-mography revealed stones in the left intrahepatic ductthat were missed at the time of lithotripsy. Echographyperformed regularly as a follow-up study for nine patientsof cholecystolithiasis revealed new formation of debris inthe gallbladder in only one patient 10 months after litho-tripsy. Ursodesoxycholic acid and hymecromone were

given to this patient for 2 months, which resulted in dis-appearance of the debris.

Discussion

As described in this report, the use of electrohydrauliclithotripsy either via the percutaneous transhepatic routeor through the T-tube track has enabled us to removestones from the common bile duct, intrahepatic ducts,and even the gallbladder. Even large immobile stones weresuccessfully removed after fragmentation once the stoneswere localized under direct vision by choledochoscopy.The success or failure did not depend on the nature ofthe stones; even hard, calcified cholesterol stones couldbe fragmented.

Removal of large stones from the biliary tract has beena challenge for percutaneous choledochoscopic lithotomy.We previously dilated the PTBD tract up to 26 Frenchsize to extract a stone of 8 mm in diameter,9 but the di-latation was associated with considerable pain. Althoughseveral types of forceps have been devised, forceps lithot-omy has been time-consuming and not always success-ful.10 Presence of bile duct stricture may prohibit the ef-ficient use ofthe forceps. YAG laser has been used duringcholedochoscopy;"I2 however current laser lithotripsy hasmany disadvantages. Lasers do not crush a cholesterolstone satisfactorily, the equipment is expensive, laser de-livery needs a water-supplying system, and a quartz fiberto transmit the laser beam is too fragile to be manipulatedeasily through a choledochoscope and too stiffto be usedin small tortuous bile ducts. Electrohydraulic lithotripsyis not associated with any of these drawbacks.

As shown by the number of choledochoscopy sessionsand period oftime for complete lithotomy, common bileduct stones were most easily removed, chiefly because thecommon bile duct was straight, allowing easy choledo-choscopic access to the stones, and the number of stoneswas small. Most of the patients had all their stones elim-inated in three sessions; 1 for lithotripsy, 1 for extractionof the fragments, and 1 for confirmation of completeclearance of the fragments. This method will be quite anaddition to the treatment ofcommon bile duct stones and

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582 YOSHIMOTO AND OTHERS Ann. Surg.-November 1989

is the choice in cases of large or impacted stones that arenot removable by EST.

Previously we reported usefulness ofcholedochoscopicelectrohydraulic lithotripsy for the treatment of intrahe-patic stones.8 This seems to be the first choice ofthe treat-ment in patients who are poor surgical risks. Furthermorecholedochoscopic lithotomy before surgery may also bejustified even in patients without any risk factors.13 Anappropriate operative procedure for the treatment of he-patolithiasis should be selected on the basis ofanatomicallocation of bile duct stricture often associated with thisdisease. This can be achieved more accurately after com-plete removal ofthe intrahepatic stones because bile ductstricture tends to be improved after removal ofthe stones.The combination of choledochoscopic lithotomy andelectrohydraulic lithotripsy would allow for quick removalof the stones before the surgical procedure is planned.

Cholecystectomy is a relatively safe method for thetreatment of stones in the gallbladder. However it carriessome risk when the procedure is to be done in high-riskpatients. A variety of alternatives such as medical orchemical dissolution and extracorporeal shock wavelithotripsy are now under investigation, but none ofthemhas yet proved satisfactory.6'7 With the combined use ofpercutaneous transhepatic cholecystoscopy'4 and elec-trohydraulic lithotripsy, we treated poor-risk patients withgallstones or a so-called confluence stone. The confluencestone is an extremely complicated condition in which astone lodged right at the junction of the cystic duct andcommon bile duct causes cholangitis and jaundice. APTBD reduces jaundice and at the same time providesa route for choledochoscopic lithotripsy and lithotomy(Fig. 1).A major drawback of choledochoscopic lithotripsy is

that it takes at least 3 weeks for dilatation and maturationof the percutaneous track before choledochoscopy is at-tempted. To shorten the period for establishing the per-cutaneous track, we are now conducting a new trial inwhich PTBD and dilatation are performed on the sameday under epidural anesthesia and choledochoscopy isstarted in a week using an overtube to protect the sinustract. The results ofthis trial will be the subject ofa futurereport. Fragmentation and removal of the stones in thegallbladder needs even a longer period than stones in thecommon bile duct and intrahepatic ducts because thegallstones are usually hard, large, and multiple. Additionalproblems associated with lithotripsy of the gallstones arethat fragments after lithotripsy may migrate into thecommon bile duct and require EST to remove them, andthat gallstones may reform after a certain period of time,as seen in one of our patients 10 months after lithotomy.These problems must await future investigation to be re-solved.

Complications encountered in this series include minorbleeding and shivering chills. The bleeding occurred dueto friction of the ductal wall by the sharp edge of the tipof the lithotripsy probe. Therefore the metal ring at theprobe tip has been refined into smoother shape, leadingto a decrease in the incidence of such bleeding. The cho-ledochoscopic view was often blurred by blood, dispersedfragments, and bubbles. The use of the large-caliber cho-ledochoscope was helpful to keep the view clear due tothe larger channel for perfusion. However instillation ofa large amount of saline into the biliary tract might causeundesirable elevation ofductal pressure. In fact, shiveringchills and fever probably due to cholangiovenous refluxoccurred in three of our patients. Development of a cho-ledochoscope with two catheter channels for perfusionand suction would be mandatory to overcome thisproblem.

References

1. Safrany L. Endoscopic treatment of biliary-tract disease: an inter-national study. Lancet 1987; ii:983-985.

2. Ikeda S, Tanaka M, Yoshimoto H, Matsumoto S. Endoscopicsphincterotomy: nine years' experience using a long-tippedsphincterotome. In Okabe H, Honda T, Oshiba 5, eds. EndoscopicSurgery. Amsterdam: Elsevier Science Publishers, 1984. p. 47-55.

3. Yamakawa T, Mieno K, Noguchi T, Shikata J. An improved cho-ledochofiberscope and non-surgical removal of retained biliarycalculi under direct visual control. Gastrointest Endosc 1976; 22:160-164.

4. Nimura Y, Hayakawa N, Toyoda S, et al. Percutaneous transhepaticcholangioscopy (PTCS). Stomach Intestine (I to Cho) 1981; 16:681-689.

5. Thistle JL, Carson GL, Hofmann AF, et al. Monooctanoin, a dis-solution agent for retained cholesterol gallstone: physical prop-erties and clinical application. Gastroenterology 1980; 78:1016-1022.

6. Bachrach WH, Hofmann AF. Ursodeoxycholic acid in the treatmentof cholesterol cholelithiasis. Dig Dis Sci 1982; 27:833-856,

7. Sauerbruch T, Delius M, Paumgartner G, et al. Fragmentation ofgallstones by extracoporeal shock waves. New Eng J Med 1986;314:818-822.

8. Matsumoto S, Tanaka M, Yoshimoto H, et al. Electrohydrauliclithotripsy ofintrahepatic stones during choledochoscopy. Surgery1987; 102:852-856.

9. Tanaka M, Yoshimoto H, Ikeda S, et al. Two approaches for elec-trohydraulic lithotripsy in the common bile duct. Surgery 1985;98:313-318.

10. Komaki F, Yamakawa T, Shikata J. Newly deviced forceps for non-surgical removal of intrahepatic stones. Progress of Digestive En-doscopy 1976; 9:65-68.

11. Orii K, Ozaki A, Takase Y, Iwasaki Y. Lithotomy of intrahepaticand choledochal stones with Yag laser. Surg Gynecol Obstet 1983;156:485-488.

12. Yamazaki Y. Basic and clinical investigation of cholangioscopic li-thotomy. Gastroenterol Endosc 1985; 27:27-43.

13. Nimura Y, Hayakawa J, Toyoda S, et al. Endoscopic treatment ofintrahepatic stone. Stomach and Intestine (I to Cho) 1984; 16:437-444.

14. Inui K, Nakae Y, Nakamura J, et al. Percutaneous transhepaticcholecystoscopy (PTCCS). Gastroenterol Endosc 1983; 25:636-643.