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

Superior gallstone dissolubility and safety of tert-amyl ethyl ether over methyl-tertiary butyl ether

BACKGROUND

The use of methyl-tertiary butyl ether (MTBE) to dissolve gallstones has been limited due to concerns over its toxicity and the widespread recognition of the safety of laparoscopic cholecystectomy. The adverse effects of MTBE are largely attributed to its low boiling point, resulting in a tendency to evaporate. Therefore, if there is a material with a higher boiling point and similar or higher dissolubility than MTBE, it is expected to be an attractive alternative to MTBE.

AIM

To determine whether tert-amyl ethyl ether (TAEE), an MTBE analogue with a relatively higher boiling point (102 °C), could be used as an alternative to MTBE in terms of gallstone dissolubility and toxicity.

METHODS

The in vitro dissolubility of MTBE and TAEE was determined by measuring the dry weights of human gallstones at predetermined time intervals after placing them in glass containers with either of the two solvents. The in vivo dissolubility was determined by comparing the weights of solvent-treated gallstones and control (dimethyl sulfoxide)-treated gallstones, after the direct infusion of each solvent into the gallbladder in both hamster models with cholesterol and pigmented gallstones.

RESULTS

The in vitro results demonstrated a 24 h TAEE-dissolubility of 76.7%, 56.5% and 38.75% for cholesterol, mixed, and pigmented gallstones, respectively, which represented a 1.2-, 1.4-, and 1.3-fold increase in dissolubility compared to that of MTBE. In the in vitro experiment, the 24 h-dissolubility of TAEE was 71.7% and 63.0% for cholesterol and pigmented gallstones, respectively, which represented a 1.4- and 1.9-fold increase in dissolubility compared to that of MTBE. In addition, the results of the cell viability assay and western blot analysis indicated that TAEE had a lower toxicity towards gallbladder epithelial cells than MTBE.

CONCLUSION

We demonstrated that TAEE has higher gallstone dissolubility properties and safety than those of MTBE. As such, TAEE could present an attractive alternative to MTBE if our findings regarding its efficacy and safety can be consistently reproduced in further subclinical and clinical studies.

Efficacy and safety of a novel topical agent for gallstone dissolution: 2-methoxy-6-methylpyridine

BACKGROUND

Although methyl-tertiary butyl ether (MTBE) is the only clinical topical agent for gallstone dissolution, its use is limited by its side effects mostly arising from a relatively low boiling point (55 °C). In this study, we developed the gallstone-dissolving compound containing an aromatic moiety, named 2-methoxy-6-methylpyridine (MMP) with higher boiling point (156 °C), and compared its effectiveness and toxicities with MTBE.

METHODS

The dissolubility of MTBE and MMP in vitro was determined by placing human gallstones in glass containers with either solvent and, then, measuring their dry weights. Their dissolubility in vivo was determined by comparing the weights of solvent-treated gallstones and control (dimethyl sulfoxide)-treated gallstones, after directly injecting each solvent into the gallbladder in hamster models with cholesterol and pigmented gallstones.

RESULTS

In the in vitro dissolution test, MMP demonstrated statistically higher dissolubility than did MTBE for cholesterol and pigmented gallstones (88.2% vs. 65.7%, 50.8% vs. 29.0%, respectively; P < 0.05). In the in vivo experiments, MMP exhibited 59.0% and 54.3% dissolubility for cholesterol and pigmented gallstones, respectively, which were significantly higher than those of MTBE (50.0% and 32.0%, respectively; P < 0.05). The immunohistochemical stains of gallbladder specimens obtained from the MMP-treated hamsters demonstrated that MMP did not significantly increase the expression of cleaved caspase 9 or significantly decrease the expression of proliferation cell nuclear antigen.

CONCLUSIONS

This study demonstrated that MMP has better potential than does MTBE in dissolving gallstones, especially pigmented gallstones, while resulting in lesser toxicities.

Advances of recurrent risk factors and management of choledocholithiasis

Gallstone disease is a common and frequently occurring disease in human, and it is the main disease among the digestive system diseases. The incidence of gallstone disease in western countries is about 5%-22%, and common bile duct stones (CBDS) accounts for 8%-20%. CBDS easily lead to biliary obstruction, secondary cholangitis, pancreatitis, and obstructive jaundice, even endanger life. Therefore, it needs timely treatment once diagnosed. The recurrence of choledocholithiasis after bile duct stones clearance involves complicated factors and cannot be completely elaborated by a single factor. The risk factors for recurrence of choledocholithiasis include bacteria, biliary structure, endoscopic and surgical treatment, and inflammation. The modalities for management of choledocholithiasis are endoscopic retrograde cholangiopancreatography (ERCP), laparoscopic or open common bile duct exploration, dissolving solutions, extracorporeal shockwave lithotripsy (ESWL), percutaneous radiological interventions, electrohydraulic lithotripsy (EHL) and laser lithotripsy. We compare the different benefits between surgery and ERCP. And finally, we make a summary of the current strategy for reducing the recurrence of CBDS and future perspectives for CBDS management.

Modern management of common bile duct stones

It is imperative for gastroenterologists to understand the different formations of bile duct stones and the various medical treatments available. To minimize the complications of endoscopic retrograde cholangiopancreatography (ERCP), it is critical to appropriately assess the risk of bile duct stones before intervention. Biliary endoscopists should be comfortable with the basic techniques of stone removal, including sphincterotomy, mechanical lithotripsy, and stent placement. It is important to be aware of advanced options, including laser and electrohydraulic stone fragmentation, and papillary dilatation for problematic cases. The timing and need for ERCP in those who require a cholecystectomy is also a consideration.

Endoscopic extraction of large common bile duct stones: A review article

Since therapeutic endoscopic retrograde cholangiopancreatography replaced surgery as the first approach in cases of choledocolithiasis, a plethora of endoscopic techniques and devices appeared in order to facilitate rapid, safe and effective bile duct stones extraction. Nowadays, endoscopic sphincterotomy combined with balloon catheters and/or baskets is the routine endoscopic technique for stone extraction in the great majority of patients. Large common bile duct stones are treated conventionally with mechanical lithotripsy, while the most serious complication of the procedure is “basket and stone impaction” that is predominately resolved surgically. In cases of difficult, impacted, multiple or intrahepatic stones, more sophisticated procedures have been used. Electrohydraulic lithotripsy and laser lithotripsy are performed using conventional mother-baby scope systems, ultra-thin cholangioscopes, thin endoscopes and ultimately using the novel single use, single operator SpyGlass Direct Visualization System, in order to deliver intracorporeal shock wave energy to fragment the targeted stone, with very good outcomes. Recently, large balloon dilation after endoscopic sphincterotomy confirmed its effectiveness in the extraction of large stones in a plethora of trials. When compared with mechanical lithotripsy or with balloon dilation alone, it proved to be superior. Moreover, dilation is an ideal alternative in cases of altered anatomy where access to the papilla is problematic. Endoscopic sphincterotomy followed by large balloon dilation represents the onset of a new era in large bile duct stone extraction and the management of “impaction” because it seems that is an effective, inexpensive, less traumatic, safe and easy method that does not require sophisticated apparatus and can be performed widely by skillful endoscopists. When complete extraction of large stones is unsuccessful, the drainage of the common bile duct is mandatory either for bridging to the final therapy or as a curative therapy for very elderly patients with short life expectancy. Placing of more than one plastic endoprostheses is better while the administration of Ursodiol is ineffective. The great majority of patients with large stones can be treated endoscopically. In cases of unsuccessful stone extraction using balloons, baskets, mechanical lithotripsy, electrohydraulic or laser lithotripsy and large balloon dilation, the patient should be referred for extracorporeal shock wave lithotripsy or a percutaneous approach and finally surgery.

ESWL for difficult bile duct stones: A 15-year single centre experience

AIM: To evaluate the efficacy of extracorporeal shock wave lithotripsy (ESWL) for the management of refractory bile duct cholelithiasis in a third level referral centre.

METHODS: The clinical records of all patients treated with a second generation electromagnetic lithotripter (Lithostar Plus, SIEMENS) from October 1990 to April 2005 were evaluated. All patients were monitored during the procedure and antibiotics were administered in case of cholangitis. The χ² test and logistic regression analysis were performed as appropriate.

RESULTS: Two hundred and fourteen patients (102 males, 112 females; mean age 74.8 ± 0.84 years - single stone 97, multiple stones 117) underwent ESWL. The mean number of sessions and shock waves were 3.5 ± 0.13 and 3477.06 ± 66.17, respectively. The maximum stone size was 5 cm. Complete stone clearance was achieved in 192 (89.7%) patients. Of the remaining patients 15 required surgery, 2 a palliative stent and in 5 patients stone fragmentation led to effective bile drainage with clinical resolution despite incomplete clearance. Age, sex and stone characteristics were not related to treatment outcome. Major complications occurred in two patients (haemobilia and rectal bleeding) and minor complications in 25 (3 vomiting, 22 arrhythmias). No procedure-related deaths occurred.

CONCLUSION: ESWL is a safe and effective technique for clearance of refractory bile duct stones.

Extracorporeal shock-wave lithotripsy for bile duct calculi

BACKGROUND

Bile duct calculi (BDC) can be cleared or treated with modern endoscopic techniques in most patients. However, large stones, bile duct strictures, or unusual anatomy may make endoscopic clearance difficult. The purpose of the present study was to determine the efficacy of extracorporeal shock-wave lithotripsy (ESWL) in treating patients with complicated BDC.

METHODS

Between 1989 and January 1995, 16 patients with BDC were treated at our institution with ESWL using a Dornier HM-3 lithotropter. The average age of patients was 62 years (range 32 to 88). Endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy and attempted stone extraction (100%), nasobiliary drainage (83%), and biliary stents (6%) were used prior to ESWL. Eleven patients (61 %) had solitary stones, ranging in diameter from 0.5 to 2.6 cm, whereas 7 patients had multiple stones, ranging in diameter from 0.5 to 5.0 cm. The indications for ESWL were stone impaction (56%), stone size (38%), and bile duct stricture (6%).

RESULTS

The 16 patients received 27 ESWL treatments (mean = 2101 shock at 21 kV); with 4 patients (22%) requiring multiple treatments. Stone fragmentation was achieved in 94% of patients. All patients had ERCP performed post-ESWL, and only 2 (13%) patients required immediate operations. At discharge, 94% of patients were stone-free. Minor complications (eg, pain, hematuria) were common. With an average follow-up of 3 years, only 1 patient (6%) has required retreatment for BDC. Hepatic transplantation was required in an additional patient.

CONCLUSIONS

In this cohort of patients with both major medical comorbidities and/or technical contraindications to standard methods of endoscopic and surgical clearance of BDC, we found that ESWL facilitated stone clearance in 94% of patients with minimal morbidity and no mortality. In our opinion, ESWL should be used more frequently in the treatment of these complex patients.

Contact solvents for common bile duct stones. Study in an in vitro system

Cholesterol and brown pigment stones found in the common bile duct are often radiolucent and therefore indistinguishable. The purpose of this study was to define contact solvent systems able to dissolve both stone types. The influence of mucolytic agents on in vitro pigment stone dissolution was first determined. It was shown that dithioerythritol induced more rapid dissolution than N-acetylcysteine. Alternating treatment with an aqueous alkaline solvent (pH = 9.5), composed of sodium deoxycholate 50 mM, ethylenediaminetetraacetate 26 mM and dithioerythritol 50 mM, for 45 min, and an organic solvent methyl tert-butyl ether/dimethyl sulfoxide (90/10) for 15 min, was more effective for bilirubin, cholesterol, and fatty acid solubilization (p < 0.01) than using these solvents separately. The dissolution of brown stones was nearly completed within 9 h and that of mixed cholesterol stones was obtained within 3 h. We conclude that the alternating treatment described is very effective for the rapid in vitro dissolution of the two major stone types present in the bile ducts, and deserves further assessment in vivo.

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)