Choledocholithiasis--in vivo stone dissolution using methyl tertiary butyl ether (MTBE)

A history of the dissolution of retained choledocholithiasis

BACKGROUND

Common duct calculi retained after gallbladder surgery continue to present a clinical challenge especially in the era of minimally invasive surgery. This review examines the strategy of dissolution therapy used throughout the history of biliary tract surgery and its use to the modern surgeon.

DATA SOURCES

Original journal articles and reviews were identified using standard surgical textbooks and MEDLINE. Keywords for searching included choledocholithiasis, dissolution, mono-octanoin, common duct stones, MTBE, cholic acid, and gallstones.

CONCLUSIONS

Dissolution therapy used initially as an alternative to open surgery is now used more effectively as an adjunct to laparoscopic or endoscopic biliary tract surgery. The current review demonstrates a majority of patients with retained choledocholithiasis respond to dissolution and can be safely managed without choledochotomy.

Methyl tertiary butyl ether in human blood after exposure to oxygenated fuel in Fairbanks, Alaska

Residents of Fairbanks, Alaska reported health complaints when 15%, by volume, methyl tertiary butyl ether (MTBE) was added to gasoline during an oxygenated fuel program. We conducted an exposure survey to investigate the effect of the program on human exposure to MTBE. We studied 18 workers in December 1992 during the program and 28 workers in February 1993 after the program was suspended. All workers were heavily exposed to motor vehicle exhaust or gasoline fumes. In December, the median post-shift blood concentration of MTBE in the workers was 1.8 micrograms/l (range, 0.2-37.0 micrograms/l), and in February the median post-shift blood concentration of MTBE in the 28 workers was 0.24 micrograms/l (range, 0.05-1.44 micrograms/l; p = .0001). Blood MTBE levels were measurably higher during the oxygenated fuel program in Fairbanks than after the program was suspended.

Utility of biliary microcrystal analysis in predicting composition of common bile duct stones

The high failure rate of contact litholytic therapy for common bile duct stones with currently available cholesterol solvents has been attributed to the inclusion of patients with pigment stones, as no pretreatment investigation is undertaken to distinguish the two stone types. In 36 patients with common bile duct stones we prospectively evaluated the utility of microscopic examination of bile collected from the biliary tree in predicting stone composition. The bile, obtained by means of either an endoscopically placed nasobiliary catheter (n = 27) or a surgically placed T-tube (n = 9), was subjected to microscopic examination, and findings were compared with the composition of stones retrieved subsequently. On the basis of quantitative infrared spectroscopy, stones were classified as cholesterol (n = 28) or pigment (n = 8) stones. The presence of cholesterol crystals in bile correctly identified 24 of 28 patients with cholesterol stones (sensitivity, 86%; specificity, 100%; positive predictive value, 100%). Calcium bilirubinate granules, when present alone (without cholesterol crystals), correctly identified all eight patients with pigment stones (sensitivity, 100%; specificity, 89%; positive predictive value, 73%). Thus, microscopic examination of bile from the biliary tree, if used as a pretreatment screening test, may help distinguish between patients with cholesterol and pigment stones and thereby considerably improve the results of litholytic therapy of common bile duct stones with currently available solvents.

Health effects of oxygenated fuels

The use of oxygenated fuels is anticipated to increase over the next decades. This paper reviews the toxicological and exposure information for methyl tertiary-butyl ether (MTBE), a fuel additive, and methanol, a replacement fuel, and discusses the possible health consequences of exposure of the general public to these compounds. For MTBE, the health effects information available is derived almost exclusively from rodent studies, and the exposure data are limited to a few measurements at some service stations. Based on these data, it appears unlikely that the normal population is at high risk of exposure to MTBE vapor. However, in the absence of health and pharmacokinetic data in humans or in nonhuman primates, this conclusion is not strongly supported. Similarly, there are a number of uncertainties to take into consideration in estimating human risk from the use of methanol as a fuel. Although methanol may be toxic to humans at concentrations that overwhelm certain enzymes involved in methanol metabolism, the data available provide little evidence to indicate that exposure to methanol vapors from the use of methanol as a motor vehicle fuel will result in adverse health effects. The uncertainties in this conclusion are based on the lack of information on dose-response relationship at reasonable, projected exposure levels and of studies examining end points of concern in sensitive species. In developing a quantitative risk assessment, more needs to be known about health effects in primates or humans and the range of exposure expected for the general public for both compounds.

Combined laparoscopic and endoscopic management of cholelithiasis and choledocholithiasis

With the advent of laparoscopic cholecystectomy, optimal management of common duct stones remains controversial. Seven hundred six patients underwent laparoscopic cholecystectomy in our institution from January 1990 through January 1992. From this group of patients, 50 were identified as having clinical or radiographic evidence of common duct stones. Thirty-one patients demonstrated preoperative risk factors for common duct stones and underwent preoperative endoscopic retrograde cholangiopancreatography (ERCP). The risk factors included jaundice (19%), pancreatitis (23%), elevated liver function tests (52%), and ultrasound evidence of choledocholithiasis (6%). Preoperative ERCP was performed in 94% of patients. There were two failures due to periampullary diverticula. Common duct stones were identified in 18 patients (62%) and successfully removed by endoscopic sphincterotomy in all of these patients. Nineteen patients were found to have unsuspected common duct stones on intraoperative cholangiography. Eighteen patients (95%) underwent successful ERCP and endoscopic sphincterotomy with stone extraction. Overall, major morbidity was 2% and included one patient who experienced endoscopic sphincteroplasty. The three endoscopic failures were managed by open common duct exploration, laparoscopic duct exploration, and combined laparoscopic and open common duct exploration. We conclude that combined laparoscopic and endoscopic therapy is a viable option for the management of cholelithiasis with choledocholithiasis.

Non-surgical management of bile duct stones refractory to routine endoscopic measures

Endoscopic sphincterotomy and percutaneous approaches to the biliary tract have revolutionized the treatment of bile duct stones. Both the endoscopic and transhepatic approaches are less invasive than open surgery. This is an advantage for the mostly elderly and frail patients with common bile duct stones. Other patients with intrahepatic stones, e.g. young patients with oriental lithiasis, may also profit from the non-surgical approach. In this latter group it is often difficult for the surgeon to obtain access to the stone-bearing bile ducts. Due to the anatomical situation, size or impaction of stones the non-surgical approach, including mechanical disintegration, may primarily fail. Several techniques such as intracorporeal lithotripsy using electrohydraulic probes or laser light, extracorporeal shockwave lithotripsy or direct contact dissolution are now available and often allow complete clearance of the bile ducts. If a kidney lithotripter with radiographic devices is available, it should be used after an attempt at mechanical lithotripsy has failed (Figure 1). According to the literature, experience with this method is greater than with any other 'third-step approach'. The procedure is simple, relatively safe and successful in approximately 80% of patients. However, in at least one third of patients, several sessions have to be performed and further endoscopy is frequently required for extraction of fragments. Intracorporeal techniques may become the procedure of choice in the future, at least in patients with common bile duct stones. At the moment, however, the different devices are still not fully developed and too susceptible to damage. A further major drawback, especially with high-energy electrohydraulic intracorporeal lithotripsy, is the danger of bile duct injury or even perforation, so that most procedures must be performed under optical control. The use of contact dissolution cannot generally be recommended. Treatment with mono-octanoin or modified mono-octanoin solvents takes too long, is often not successful and has a high rate of side-effects. MTBE may shorten the procedure considerably, but is suitable only for cholesterol stones, and the danger of spill-over into the intestine with absorption and systemic side-effects has to be weighed against the probability of success.

Acute effects of topical methyl tert-butyl ether or ethyl propionate on gallbladder histology in animals: a comparison of two solvents for contact dissolution of cholesterol gallstones

Experiments were performed in anesthetized rabbits and piglets to assess gallbladder mucosal injury during irrigation with methyl tert-butyl ether, a C5 ether, or ethyl propionate, a C5 ester--two organic solvents used in the contact dissolution of cholesterol gallstones. In 44 New Zealand White rabbits, the gallbladder was exposed to individual solvents or saline solution through a transhepatic catheter for 2 hr. Gallbladders were then harvested and fixed immediately or after a recovery period of 1, 4 or 8 days. Tissue sections were examined under light microscopy, and severity of injury was graded with predefined criteria by two pathologists blinded to the animals' treatment regimens. Histological assessment showed severe mucosal injury such as necrosis of the cells at the villus tips immediately after 2 hr of exposure to either solvent. After 4 days, injury had decreased significantly; after 8 days, complete mucosal healing had taken place. A similar study was performed in 32 piglets. Solvent or saline solution was oscillated in and out of the gallbladders of these piglets with a computer-controlled syringe pump at a pressure less than the leakage pressure of the gallbladder. Histological assessment was performed on tissue samples obtained immediately after the procedure or 8 days later. Both solvents caused severe mucosal injury; however, after 8 days complete mucosal healing had occurred, so that gallbladders exposed to solvent were indistinguishable from gallbladders exposed to saline solution, which was used as control. We conclude that both methyl tert-butyl ether and ethyl propionate cause moderate to severe epithelial injury but that the gallbladder epithelium regenerates within a few days.(ABSTRACT TRUNCATED AT 250 WORDS)

Gallstone disease. Pathophysiology, epidemiology, natural history, and treatment options

In 1991, only symptomatic gallstones should be treated. The treatment of choice for all gallstones continues to be surgical removal. Except for stones in the common bile duct, which are amenable to removal by endoscopic papillotomy, nonsurgical treatment of gallstones should be investigated further before it can have widespread applicability. The major challenge in the future may be medical prevention of gallstone formation in susceptible individuals. Laparoscopic cholecystectomy seems to have moved to the forefront of surgical therapy in patients who are candidates for the procedure.

Endoscopic management of bile duct stones

The surgical risk of common duct exploration for the treatment of biliary calculi is considerably higher than that of cholecystectomy. Therefore, introduction of endoscopic sphincterotomy in 1974 was a major advance. It has become the therapy of choice in cholecystectomized patients or in those with an increased operative risk. Endoscopic sphincterotomy has a mortality rate of around 1% and a morbidity rate of 7%. These figures compare favourably with open surgery, especially in old patients. The procedure fails in about 10% of all patients referred for endoscopic removal of their calculi. However, several techniques have been described or are currently under evaluation to overcome these failures: intracorporeal or extracorporeal lithotripsy, long-term stenting of the bile duct, or direct application of solvents. Long-term follow-up studies show that between 2% and 20% of successfully managed patients may develop recurrent stones, mainly caused by bile stasis and infection. Patients with a functioning gall-bladder and no concomitant gall-bladder stones probably do not require cholecystectomy after successful endoscopic treatment of their choledochal stones. While endoscopic stone removal has replaced surgery in the elderly frail patients it has no major advantages in the young and fit patients, especially when the gall-bladder is still in situ.

Methyl tert-butyl ether in the endoscopic treatment of common bile duct radiolucent stones in elderly patients with nasobiliary tube

Methyl tert-butyl ether is an effective dissolution agent for cholesterol stones. The aim of this work was to evaluate the effect of methyl tert-butyl ether on radiolucent common bile duct stones in patients in whom endoscopic extraction has failed. From September 1985 to September 1987, 1374 patients underwent endoscopic retrograde cholangiopancreatography in our Liver Unit. An endoscopic sphincterotomy was indicated in 195 patients with common bile duct (CBD) stones because of an age over 65 years and/or surgical contraindications. Endoscopic sphincterotomy was efficient in 187 patients, allowing complete stone removal in association with conventional endoscopic methods and mechanical lithotripsy in 170 patients. Twelve of the 17 patients with failure of conventional endoscopic treatments were either older than 75 years (11 patients; mean age, 86 +/- 4.5 years) or exhibited a surgical contraindication. Stones completely obstructed CBD in six patients and had a diameter exceeding 25 mm in the six other patients. These subjects were selected for stone dissolution by methyl tert-butyl either (MTBE) according to the following protocol. MTBE was directly infused into CBD through a nasobiliary catheter, twice daily for 4-13 days (mean, seven days). Bile duct opacification, repeated after MTBE treatment, revealed the complete disappearance of CBD stones in one patient, a decrease in stone size in five patients and no change in the six other patients. MTBE treatment was well tolerated except in three patients who complained from transient abdominal pains and nausea. At the second attempt of endoscopic treatment, CBD stones were found to be softened and easily broken up, allowing a complete clearance in six patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A 10 year single centre experience of percutaneous and endoscopic extraction of bile duct stones with T tube in situ

A non-randomised single centre study of 226 consecutive patients referred over 10 years with retained common bile duct stones and a T tube in situ or a cholecystostomy tube are reported. Percutaneous extraction was attempted in 204 and endoscopic extraction in 68 patients. Percutaneous clearance was achieved in 158 (77.5%) patients and endoscopic clearance in 52 (76.5%) patients. Six of 153 (3.9%) patients followed after percutaneous treatment suffered major complications (pancreatitis, cholangitis, or tract perforation). Three of 67 (44%) patients followed after endoscopic treatment suffered major complications (pancreatitis, cholangitis, or bleeding). When the initial method of treatment failed, the alternative was used, resulting in an overall success rate of bile duct clearance of 94.3%. It is concluded that percutaneous and endoscopic methods of bile duct clearance in patients with a T tube in situ are equally effective, carrying similar complication rates. This study has helped to clarify the indications and efficacy of these alternative treatments.

Percutaneous flexible choledochoscopy: a simple method for retained common bile duct stone removal

Conventional methods of treatment of retained common bile duct stones found on T tube cholangiography after common bile duct exploration include percutaneous extraction under fluoroscopic control and endoscopic sphincterotomy. Four cases of percutaneous stone extraction under direct vision using the flexible choledochoscope are described. Clearance of the bile ducts was achieved at one sitting in three cases and four sittings in one case. Follow-up tube cholangiography was performed in two cases and confirmed complete clearance. Percutaneous endoscopic stone extraction can be performed by any surgeon with experience of flexible choledochoscopy and offers the advantages of a minimally invasive procedure without the use of specialized equipment.

Percutaneous dissolution of gallstones

Contact dissolution with MTBE is an effective and safe method to treat symptomatic patients with cholesterol gallstones. Personnel, time, and safety factors have limited widespread use of the procedure. With current competing methods to treat gallstones, it is likely that MTBE use will be reserved for those patients who elect percutaneous therapy due to fear of surgery or anesthesia and in those elderly patients who are compromised by underlying medical conditions.

Extracorporeal shock wave treatment of common bile duct stones: experience with two different lithotriptors at a single institution

Extracorporeal shock wave lithotripsy (ESWL) is a new treatment modality for retained common bile duct stones. Sixty-two patients (mean age 75 years, range 27-95 years) with retained common bile duct stones were treated with two different lithotriptors. One of the lithotriptors operated on the electrohydraulic principle (Dornier HM-3) (n = 13), the other on the electromagnetic principle (Siemens Lithostar) (n = 49). All HM-3 patients were treated under general anaesthesia, whereas with the Lithostar one patients was treated under general anaesthesia, 43 received analgesia and sedation and five had no analgesia at all. Patients treated with the Lithostar had more sessions (mean 1.9 versus 1.3, P less than 0.05) and needed more stock waves (mean 8611 versus 2534, P less than 0.001) than patients treated with the HM-3. Fragmentation was achieved in all patients treated with the HM-3 and in 42 (86 per cent) patients treated with the Lithostar. In this latter group ten patients underwent common bile duct exploration without complications. Eleven patients had transient haematuria after treatment with the HM-3 and two patients (one in each group) had a subcapsular haematoma of the right kidney, all without clinical sequelae. At follow-up (median: HM-3 43 months, Lithostar 18 months), none of the patients had biliary complaints. We conclude that ESWL of retained common bile duct stones in safe and effective with both lithotriptors and should be considered before surgery in the elderly or high-risk patient.

Choledocholithiasis. Endoscopic sphincterotomy or common bile duct exploration

A prospective randomized trial was conducted of preoperative endoscopic sphincterotomy and surgery (ES&S) or surgery alone (SA) in 52 patients with cholecystolithiasis and choledocholithiasis that were candidates for elective surgery. After ES&S 65% of patients were stone free. Eighty-eight per cent of patients with SA were stone free after surgery (p less than 0.05). Three patients in each group had residual stones at the completion of the operation. Five of these six had more than 20 common bile duct (CBD) stones. There was one episode of major hemorrhage in a patient in each group and no deaths. Costs were essentially equal for the individual patient with a successful ES as compared to SA. Societal costs of a program of preoperative endoscopic retrograde cholangiopancreatography and ES would be higher because of the cost of screening for patients with CBD stones. These results do not support preoperative ES as a technique for clearance of the CBD of stones on the basis of efficacy, morbidity rate, or cost.

Early endoscopic sphincterotomy for retained bile duct stones after gallbladder surgery

Endoscopic sphincterotomy (ES) was performed in 36 patients (age range 33-88 years; median 63 years) with retained bile duct stones after cholecystectomy (32 patients) or cholecystostomy (4 patients). The median time interval between surgery and ES was 28 days (range 10-216 days). At the time of ES, 23 patients had a T-tube in situ. Clearance of the bile duct was achieved by T-tube irrigation in 15 patients, and by basket or balloon extraction in seven patients. Spontaneous clearance of the duct after ES occurred in 12 patients, while two patients required widening of the sphincterotomy to allow successful basket extraction. Complications occurred in four patients (11%). Two patients sustained significant haemorrhage from the ES site and subsequently died. One patient developed mild acute pancreatitis while another had persisting cholangitis before and after ES. Both of these patients recovered with conservative management. While ES performed soon after gallbladder surgery allows for early bile duct clearance, the small but significant risk of potentially lethal haemorrhage suggests that its use should be reserved for patients in whom other non-operative methods have failed or are inappropriate.

In vitro comparison of different gall stone dissolution solvents

Extracorporeal shockwave lithotripsy (ESWL) of gall bladder stones leaves residual fragments that need to be dissolved by chemical solvents. In this study we compared the in vitro dissolving capacity of methyl tert-butyl ether (MTBE), mono-octanoin, limonene, and limonene/mono-octanoin (70%/30%). From nine sets of five human gall stones obtained at cholecystectomy, four stones were used for dissolution and the fifth was used for chemical analysis of cholesterol, calcium, and bilirubin contents. Eight sets were cholesterol stones with a mean (SD) cholesterol content of 89.9 (5.6)%. These stones dissolved completely in either solvent, often leaving sand-like debris, with the exception of one stone. MTBE dissolved cholesterol gall stones 100 times faster than mono-octanoin and 10 times faster than limonene or the limonene/mono-octanoin mixture (p less than 0.001). The combination of limonene and mono-octanoin was as effective as limonene alone. Of the four solvents, MTBE is the best one to evaluate for dissolution of residual fragments after ESWL treatment of gall bladder stones.

Percutaneous endoscopic treatment of cholelithiasis

Surgical management of gallstones was first performed successfully in 1878. Over the past decade, several new treatment alternatives have evolved that challenge the supremacy of traditional surgical cholecystectomy. Two endoscopic alternatives, e.g., percutaneous cholecystolithotomy (PCCL) and laparoscopic cholecystectomy (LC) are the latest additions to the growing armamentarium. Our initial experience with PCCL and LC as compared with our traditional cholecystectomy experience shows a 57% reduction in hospital days, a 58% reduction in postoperative analgesic dose, and 50% or more reduction in disabling convalescence in favor of the endoscopic alternatives. A review of the efficacy and morbidity of traditional surgery, peroral drug chemolysis (PDC), shockwave lithotripsy plus PDC, and percutaneous transhepatic lavage with methyl terbutyl ether suggests that the endoscopic alternatives are less morbid than traditional surgery and more efficacious and perhaps less morbid than other non-invasive or minimally invasive alternatives. Both original data and a literature review are presented.

Non-surgical options for the management of gallstone disease: an overview

The modalities for the non-surgical treatment of gallstones include oral dissolution by bile salts, local dissolution by methyl-tert-butyl-ether (MTBE), extracorporeal shockwave lithotripsy (ESWL) and percutaneous gallstone clearance. The results of oral bile salt therapy for cholesterol stones have been disappointing, and the only indication for this treatment is after ESWL. The high efficacy initially reported for MTBE has not been confirmed by subsequent experience in other centres: this therapy is toxic and best confined to specialized centres. ESWL, though effective in noncalcified stones, has limited overall applicability (approx. 15%) and is frequently followed by recurrence despite maintenance therapy with oral bile salts. Percutaneous gallstone clearance (radiologic or laparoscopic) has been superseded by laparoscopic cholecystectomy. This offers definitive treatment in a single session and has significant advantages over open cholecystectomy in terms of short hospital stay and accelerated recovery with early return to work or full activity. Destruction of the gallbladder by sclerosant agents (chemical cholecystectomy) requires further experimental evaluation before its introduction to clinical practice.

Could activated charcoal be used to adsorb intraduodenal methyl tert-butyl ether spillage during its use in the dissolution of gallstones?

Methyl tert-butyl ether (MTBE) is becoming more frequently used in the non-surgical removal of cholesterol gallstones. However, during its introduction into the biliary tract, some spillage can occur and subsequent systemic absorption has been reported to lead to a variety of side effects. We have carried out in vitro experiments to assess the ability of activated charcoal to adsorb MTBE. A 10% aqueous suspension of activated charcoal was mixed with MTBE and its adsorption was estimated subsequently by gas chromatography. Adsorption varied from 38% at an activated charcoal: MTBE ratio of 1:1, to 96% at a ratio of 8:1. Only 3.2% of the adsorbed MTBE could be desorbed by resuspending the sedimented activated charcoal: MTBE complex in an equivalent volume of fresh distilled water. The results indicate that a single dose of activated charcoal (greater than 12 g) may be effective in minimizing systemic absorption of MTBE spilt during gallstone dissolution.

Methyl tert butyl ether dissolution therapy for common bile duct stones

Methyl tert butyl ether (MTBE) is a potent cholesterol solvent. We have used MTBE in twelve patients with 19 large radiolucent common bile duct stones which could not be removed endoscopically. MTBE was instilled directly into the common bile duct via a nasobiliary or percutaneous catheter. Successful clearance of the duct was achieved in ten patients. The stones disappeared completely in three patients with MTBE alone; in the remaining seven, it was possible to extract the stones endoscopically after MTBE, even though there was no change in the cholangiographic appearance. MTBE may have a role in the management of large retained common bile duct calculi but, given the practical difficulties of administration, its use should only be considered when other methods have failed and a non-surgical approach is desired.

Endoscopic decompression for acute cholangitis due to stones

The prognosis in patients with acute cholangitis is poor, particularly when the cholangitis is 'severe' as defined by the presence of hypotension and/or confusion. This prospective study evaluates 16 elderly patients with acute cholangitis ('severe' in 11) due to stones in whom endoscopic biliary decompression was attempted. It was technically successful on 13 (81%) of the 16 occasions and the cholangitis rapidly resolved in these patients. In seven of 13, this was the definitive treatment while six underwent subsequent surgery consisting of: cholecystectomy or cholecystostomy (five) and secondary bile duct exploration (one). Two patients died following laparotomy for stones that were not amendable to endoscopic removal. Urgent endoscopic retrograde choledochography is recommended in elderly patients with acute cholangitis, because it confirms the diagnosis and allows decompression of the biliary tract by sphincterotomy. This stabilizes the patient's general condition and facilitates subsequent open surgery when required.

Experience with MTBE as a solvent for common bile duct stones in patients with T-tube in situ

The postcholecystectomy patients who have a T-tube in situ offer a convenient route through the T-tube to perfuse solvents into the common bile duct (CBD) for dissolving any retained common duct stones. If successful, this approach is much simpler and cheaper than the usual therapeutic modality used for CBD stones, namely, endoscopic papillotomy. Thus a most potent cholesterol solvent, methyl t-butyl ether (MTBE) was perfused through the T-tube into the CBD of five patients with retained common duct stones. The dose of the solvent varied, 1.5-5 mL 0.5-1 h, given 7-13 times amounting to a total of 20-66 mL. Instillation of MTBE in the T-tube was alternated with aspiration of the bile through T-tube. Only one patient showed complete disappearance of the bile duct stone following MTBE perfusion. Others did not show any appreciable response and had to be treated by endoscopic papillotomy (three patients) or mono-octanoin perfusion (one patient). Side-effects of MTBE perfusion included pain in the abdomen in all patients, somnolence and nausea/vertigo in two patients and the smell of ether on the breath in two patients. It is concluded that MTBE is not an effective agent for dissolution of retained CBD stones in patients with T-tube in situ.

Methyl-tert-butyl-ether for treating bile duct stones: the British experience

Methyl-tert-butyl-ether (MTBE), infused via a nasobiliary catheter, was used to treat 33 patients with bile duct stones in nine units around Britain. MTBE contributed to success in 12 (36 per cent) cases: seven passed stones spontaneously during MTBE infusion and five had partial stone dissolution allowing subsequent endoscopic extraction. MTBE was non-contributory in 21 (64 per cent) cases: four passed stones after MTBE was stopped, six were treated by subsequent endoscopic techniques without evidence of dissolution, seven underwent surgery, and four were treated conservatively (with one death). In at least ten of the 21 cases in which MTBE was non-contributory, pigment stones were present. Forty-two complications occurred in 26 (79 per cent) patients. The efficacy of MTBE for treating bile duct stones might be improved by better methods of instillation and, since success may be related to technique, the use of MTBE should be restricted to units familiar with this chemical.

Dissolution of bile duct stones

Mono-octanoin can be used either alone or as an adjunct to other techniques to dissolve cholesterol bile duct stones. This solvent can be administered through an existing T tube, through the nasobiliary route, or percutaneously through the liver. Unlike basket extraction, which requires a mature T-tube sinus tract, mono-octanoin can be used immediately postoperatively or for home dissolution therapy. The endoscopic extraction of bile duct stones has a 1 percent mortality rate and a 5 to 7 percent complication rate. Special mixtures of mono-octanoin, bile acids, and ethylene diaminetetraacetic acid (EDTA) are being evaluated to dissolve pigment stones. The use of methyl tert-butyl ether is still experimental but very effective. To be most successful, mono-octanoin treatment must be used in properly selected patients.

Endoscopic sphincterotomy for bile duct stones in patients with intact gallbladders

Endoscopic sphincterotomy was performed in 121 patients (age ranged 34-92 years; median 80 years) with intact gallbladders and bile duct stones. Clearance of the duct by basket or balloon extraction was attempted in 97 patients (80 per cent) and achieved in 93 of these patients (96 per cent). In 24 patients the duct was left to empty spontaneously and this occurred in 22 patients. Immediate complications due to endoscopic sphincterotomy occurred in five patients (two haemorrhage, two perforation, one haemorrhage and perforation). Of the 101 patients reviewed 12-72 months (median 24 months) after endoscopic sphincterotomy, 76 (75 per cent) have remained asymptomatic throughout the follow-up period. Eighteen patients (18 per cent) required cholecystectomy for recurrent gallbladder symptoms 1-24 months after endoscopic sphincterotomy. One of the asymptomatic patients underwent cholecystectomy on the advice of his consultant. A further seven had recurrent biliary colic or cholangitis necessitating enlargement of the sphincterotomy and further stone retrieval in three of these patients. Endoscopic sphincterotomy is an effective treatment for bile duct stones in high risk patients, but subsequent cholecystectomy is required in a significant number of patients owing to continuing gallbladder symptoms.

Short-term effects of extracorporeal shock wave lithotripsy on the human gallbladder

Extracorporeal shock wave lithotripsy (ESWL), whereby shock wave energy is focused upon gallstones causing their disintegration into fragments sufficiently small to be passed via the biliary system, offers a promising non-invasive alternative to surgery for gallstone disease. The tissue effects in humans of ESWL are poorly characterized and no systematic study of the tissue effects of ESWL by piezoelectrically generated shock waves has been published. Sixteen patients for elective cholecystectomy were therefore subjected to ESWL before surgery and detailed histology of the gall-bladders (including scanning electron microscopy of the mucosa) was compared with that from 20 age/sex-matched control cases. The gall-bladders treated by ESWL, in addition to showing the histological changes associated with chronic cholecystitis, showed serosal vasodilatation, mural oedema, and serosal and mucosal petechial haemorrhages focally over the entire surface. Between 10 and 90 per cent epithelial denudation was observed, but all cases showed surviving columnar epithelial cells in the crypts. No case showed vascular thrombosis, tissue necrosis, or acute inflammation. These tissue effects are likely to be reversible and unlikely to present a risk of perforation, although the long-term clinicopathological effects await investigation.

Review article: dissolution of gallstones in the biliary tree

There are a variety of methods for dissolving gallstones in the biliary tree, which include oral therapy and direct contact dissolution. Cholesterol gallstones are most amenable to dissolution. Developments in non-operative physical methods to remove gallstones (particularly endoscopic papillotomy and extracorporeal shock-wave lithotripsy have diminished the use of chemical dissolution. However, in selected patients, there remains a place for chemical dissolution, but often in conjunction with the physical techniques.

Unexpected dilatation of the common bile duct after methyl tertiary butyl ether (MTBE) in rabbits. Possible implications to findings in man

Methyl tertiary butyl ether (MTBE) rapidly dissolves cholesterol gall stones in vitro and in vivo. To further characterise tolerability and safety of this aliphatic ether, either MTBE (1 ml/kg body wt daily for two days) or an equal amount of saline was infused into the common bile duct (CBD) of eight cholecystectomised rabbits. Transient vomiting, dyspnoea and somnolence developed during MTBE instillation. Post-treatment values of serum transaminases and alkaline phosphatase were significantly higher in MTBE than in saline treated animals. Cholangiography one week after the last intraductal infusion showed a five-fold increase of CBD size in MTBE v control rabbits. At autopsy histological signs of chemical cholangitis and mild duodenitis were noted in MTBE treated animals. Prompted by these findings, we performed a cholangiography in two patients who had received intraductal MTBE (about 0.2 ml/kg body wt daily for one or two days) one year before: an abnormal dilatation of the CBD was present, which might represent a specific, hitherto undescribed permanent sequela of MTBE administration.