The value of radiology in predicting gallstone type when selecting patients for medical treatment

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.

Analytic Reviews : Nonsurgical Alternatives in the Management of Gallstones

Until recently, the only therapeutic option for patients with symptomatic gallstones was surgery. However, sev eral new and innovative nonsurgical approaches are cur rently available, including oral dissolution therapy with the bile salts, ursodeoxycholic and chenodeoxycholic acids, instillation of liquid solvents such as methyl tert- butyl ether directly into the gallbladder or the common bile duct, and extracorporeal shock-wave lithotripsy. We review the role of each of these methods in the management of patients with gallstones as well as the epidemiology, pathogenesis, natural history, and radi ological characteristics of gallstones, all important con siderations when choosing appropriate treatment for the individual patient.

Efficacy of Magnesium Trihydrate of Ursodeoxycholic Acid and Chenodeoxycholic Acid for Gallstone Dissolution: A Prospective Multicenter Trial

Background/Aims

Cholecystectomy is necessary for the treatment of symptomatic or complicated gallbladder (GB) stones, but oral litholysis with bile acids is an attractive alternative therapeutic option for asymptomatic or mildly symptomatic patients. This study was conducted to evaluate the efficacy of magnesium trihydrate of ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) on gallstone dissolution and to investigate improvements in gallstone-related symptoms.

Methods

A prospective, multicenter, phase 4 clinical study to determine the efficacy of orally administered magnesium trihydrate of UDCA and CDCA was performed from January 2011 to June 2013. The inclusion criteria were GB stone diameter ≤15 mm, GB ejection fraction ≥50%, radiolucency on plain X-ray, and asymptomatic/mildly symptomatic patients. The patients were prescribed one capsule of magnesium trihydrate of UDCA and CDCA at breakfast and two capsules at bedtime for 6 months. The dissolution rate, response rate, and change in symptom score were evaluated.

Results

A total of 237 subjects were enrolled, and 195 subjects completed the treatment. The dissolution rate was 45.1% and the response rate was 47.2% (92/195) after 6 months of administration of magnesium trihydrate of UDCA and CDCA. Only the stone diameter was significantly associated with the response rate. Both the symptom score and the number of patients with symptoms significantly decreased regardless of stone dissolution. Adverse events necessitating discontinuation of the drug, surgery, or endoscopic management occurred in 2.5% (6/237) of patients.

Conclusions

Magnesium trihydrate of UDCA and CDCA is a well-tolerated bile acid that showed similar efficacy for gallstone dissolution and improvement of gallstone-related symptoms as that shown in previous studies.

Comparison on Response and Dissolution Rates Between Ursodeoxycholic Acid Alone or in Combination With Chenodeoxycholic Acid for Gallstone Dissolution According to Stone Density on CT Scan: Strobe Compliant Observation Study

Medical dissolution of gallstone is usually performed on radiolucent gallstones in a functioning gallbladder. However, absence of visible gallstone on plain abdominal x-ray does not always preclude calcification. This study aims to compare the response and dissolution rates between ursodeoxycholic acid (UDCA) alone or in combination with chenodeoxycholic acid (CDCA) according to stone density on computed tomography (CT) scan. A total of 126 patients underwent dissolution therapy with either UDCA alone or combination of CDCA and UDCA (CNU) from December 2010 to March 2014 at Korea University Ansan Hospital. In the end, 81 patients (CNU group = 44, UDCA group = 37) completed dissolution therapy for 6 months. Dissolution rate (percentage reduction in the gallstone volume) and response to therapy (complete dissolution or partial dissolution defined as reduction in stone volume of >50%) were compared between the 2 groups. Dissolution and response rates of sludge was also compared between the 2 groups. The overall response rate was 50.6% (CNU group 43.2% vs UDCA group 59.5%, P = 0.14), and the overall dissolution rate was 48.34% (CNU group 41.5% vs UDCA group 56.5%, P = 0.13). When analyzed according to stone density, response rate was 33.3%, 87.1%, 30.0%, and 6.2% for hypodense, isodense, hyperdense, and calcified stones, respectively. Response rate (85.7% vs 88.2%, P = 0.83) and dissolution rate (81.01% vs 85.38%, P = 0.17) of isodense stones were similar between CNU and UDCA group. When only sludge was considered, the overall response rate was 87.5% (CNU group 71.4% vs UDCA group 94.1%, P = 0.19), and the overall dissolution rate was 85.42% (CNU group 67.9% vs UDCA group 92.7%, P = 0.23). Patients with isodense gallstones and sludge showed much better response to dissolution therapy with CNU and UDCA showing comparable efficacy. Therefore, CT scan should be performed before medication therapy if stone dissolution is intended.

Pharmacology of bile acids and their derivatives: Absorption promoters and therapeutic agents

The role of bile acids in pharmacotherapy is reviewed in this article. The therapeutic use of bile has been recognized since ancient times. Previously bile acids were the standard treatment for gallstones where chenodeoxycholic acid and ursodeoxycholic acid were effective in promoting the dissolution of cholesterol gallstones. Today their therapeutic role looks set to expand enormously. Bile acids as absorption promoters have the potential to aid intestinal, buccal, transdermal, ocular, nasal, rectal and pulmonary absorption of various drugs at concentrations that are non-toxic. Keto derivatives of cholic acid, such as 3a,7a,dihydroxy-12-keto-5alpha-cholic acid (sodium salt and methyl ester) are potential modifiers of blood-brain barrier transport and have been shown to promote quinine uptake, enhance the analgesic effect of morphine and prolong the sleeping time induced by pentobarbital. They have also been shown to be hypoglycaemic. Bile acids as therapeutic agents have the potential to produce beneficial effects in sexually transmitted diseases, primary biliary cirrhosis, primary sclerosing cholangitis, gallstones, digestive tract diseases, cystic fibrosis, cancer and diabetes.

Gallstone dissolution with oral bile acid therapy. Importance of pretreatment CT scanning and reasons for nonresponse

In patients with cholesterol-rich gallbladder stones and a patent cystic duct, complete stone clearance rates of 65-90% have been reported with oral bile acids (OBAs) alone or with adjuvant lithotripsy (extracorporeal shock-wave lithotripsy; ESWL). The aims of the present study were to analyze pretreatment gallstone characteristics that predict the speed and completeness of dissolution with OBAs +/- ESWL, and to assess, in patients with incomplete dissolution, the reasons for the poor response. We compared pretreatment gallstone characteristics in 43 patients who became stone-free after a median of 9 months OBAs +/- ESWL with those in 43 age- and sex-matched patients whose stones failed to dissolve after two years of treatment. In those with incomplete gallstone dissolution, we repeated the oral cholecystogram and computed tomogram (CT) and, in selected patients, obtained gallbladder bile by percutaneous fine-needle puncture. In patients who became stone-free, those with stones that were isodense with bile and/or had CT scores of < 75 Hounsfield units had the fastest dissolution rates. In the 43 nonresponders, the main causes for treatment failure were impaired gallbladder contractility and acquired stone calcification. CT-lucent, noncholesterol stones, or failure of desaturation of bile with the prescribed bile acids, occurred in a minority. We conclude that the pretreatment CT attenuation score predicts both the speed and completeness of gallstone dissolution. In patients with incomplete stone dissolution, the combination of oral cholecystography, CT, and analysis of gallbladder bile will determine the underlying reasons for treatment failure in most, but not all, cases.

Gallstone dissolution with oral bile acid therapy. Importance of pretreatment CT scanning and reasons for nonresponse

In patients with cholesterol-rich gallbladder stones and a patent cystic duct, complete stone clearance rates of 65-90% have been reported with oral bile acids (OBAs) alone or with adjuvant lithotripsy (extracorporeal shock-wave lithotripsy; ESWL). The aims of the present study were to analyze pretreatment gallstone characteristics that predict the speed and completeness of dissolution with OBAs +/- ESWL, and to assess, in patients with incomplete dissolution, the reasons for the poor response. We compared pretreatment gallstone characteristics in 43 patients who became stone-free after a median of 9 months OBAs +/- ESWL with those in 43 age- and sex-matched patients whose stones failed to dissolve after two years of treatment. In those with incomplete gallstone dissolution, we repeated the oral cholecystogram and computed tomogram (CT) and, in selected patients, obtained gallbladder bile by percutaneous fine-needle puncture. In patients who became stone-free, those with stones that were isodense with bile and/or had CT scores of < 75 Hounsfield units had the fastest dissolution rates. In the 43 nonresponders, the main causes for treatment failure were impaired gallbladder contractility and acquired stone calcification. CT-lucent, noncholesterol stones, or failure of desaturation of bile with the prescribed bile acids, occurred in a minority. We conclude that the pretreatment CT attenuation score predicts both the speed and completeness of gallstone dissolution. In patients with incomplete stone dissolution, the combination of oral cholecystography, CT, and analysis of gallbladder bile will determine the underlying reasons for treatment failure in most, but not all, cases.

Gallbladder stone recurrence after medical treatment. Do gallstones recur true to type?

Medical treatments that dissolve or remove gallbladder stones but leave the gallbladder in situ have the disadvantage of gallstone recurrence. Little is known about the composition of recurrent stones or whether they recur true to type. In 21 patients with recurrent stones detected 5-74 months (mean +/- SEM, 26 +/- 4 months) after being rendered stone-free with dissolution therapy (N = 15) or percutaneous cholecystolithotomy (N = 6), we compared pretreatment and postrecurrence gallstone number, maximum gallstone attenuation scores measured by computed tomography (CT) and, in 13, the dissolvability of the recurrent stones with oral bile acids +/- extracorporeal shock-wave lithotripsy. Before treatment, five patients had solitary and 16 had multiple stones but on recurrence, the gallstones differed in number from the primary stones in 10 of the 21 patients. As a result of patient selection, before dissolution, the primary stones were all radiolucent with maximum CT scores of < 100 Hounsfield units (HU) (mean 45, range 10-84 HU). On recurrence, the stones were again CT-lucent in 13 of the 15 patients but were CT-dense in the remaining two (118 and 176 HU). Initially, all six patients treated by percutaneous cholecystolithotomy had radio-opaque stones, with a mean CT score of 459 (range 100-969) HU. However, on recurrence, only one had calcified stones (HU 140); the remaining five had CT-lucent stones (16-98 HU, P < 0.05). Of the 13 patients whose recurrent, plain x-ray-lucent and CT-lucent stones were treated with oral bile acids +/- lithotripsy, 12 (92%) showed evidence of gallstone dissolution. We conclude that gallbladder stones do not recur true to type in up to two thirds of patients. However, irrespective of original gallstone composition, recurrent stones are usually radio- and CT-lucent, presumed cholesterol-rich, and therefore potentially dissolvable with oral bile acids.

Pharmacological treatment of gallstones. Practical guidelines

Laparoscopic cholecystectomy is the treatment of choice for symptomatic cholelithiasis. Medical treatment is indicated for patients who are not fit or are afraid of surgery. For any form of medical treatment to be effective gallstones must be cholesterol rich, thus radiolucent, and the cystic duct must be patent, as indicated by gallbladder opacification on oral cholecystography. Three forms of medical treatment are currently available for clinical use--oral bile acids, bile acids as adjuncts to lithotripsy and contact dissolution using methyltertbutylether. The choice of treatment depends mainly on gallstone size. Gallstones < 6 mm in diameter are best treated with oral bile acids, chenodeoxycholic acid 15 mg/kg/day or ursodeoxycholic acid 10 mg/kg/day given alone or in combination (5 mg/kg/day each). Careful patient selection and bedtime administration of the whole daily bile acid dose enhance treatment, and may achieve up to 75% complete dissolution annually. Single stones < 30 mm in diameter or multiple stones (n < 3) are best treated with lithotripsy combined with oral bile acid for dissolution of fragments. Annual dissolution rates are about 80 and 40% for single and multiple stones, respectively. Stones of any size and number can be dissolved by direct contact dissolution using methyltertbutylether. Dissolution has been reported to be complete in almost 100% of stones, but debris is frequently left behind in the gallbladder. Following dissolution using any form of treatment, gallstones recur in about 50% of patients, and cannot be reliably prevented by low dose bile acid or dietary manipulations. Failing prevention, early detection and retreatment of recurrent stones is the best alternative option as a long term strategy.

Radiographic features of oral cholecystograms of 448 symptomatic gallstone patients: implications for nonsurgical therapy

Since radiographic findings on oral cholecystography (OCG) have implications for the eligibility for nonsurgical therapy of elderly patients, we investigated the OCGs of 448 symptomatic gallstone patients (109 male, 339 female; mean age, 49.8 +/- 14 (range, 21-88)). Opacification of the gallbladder was found in 323 cases (72.1%). Calcifications of gallstones were found in 85 opacified gallbladders (26.3%). Solitary and multiple stones were calcified in 35.3% and 18.2%, respectively (P < 0.0005). When divided into two groups (< or = 40 years and > 40 years), there was a significant increase in calcifications (P < 0.02) and a non-significant increase in opacification with increasing age. It is concluded that age is a determinant for calcification of gallstones and not opacification of the gallbladder. Since multiple stones are proportionately observed more in clinical studies than in epidemiologic studies, it is suggested that multiplicity of stones predisposes to biliary complaints. That solitary stones are more likely to be calcified than multiple stones, adds to the hypothesis that solitary and multiple stones have a different pathogenesis. Elderly patients, in whom non-surgical therapy is most likely to be indicated and cost-effective, are less likely to be suitable for this form of treatment, since age is a determinant for stone calcification.

Duodenal bile examination in identifying potential non-responders to bile salt treatment and its comparison with gall bladder bile examination

The results of bile salt treatment in patients with radiolucent stones and a functioning gall bladder have been poor. In 42 of these patients awaiting cholecystectomy we determined the value of duodenal bile examination in predicting gall stone composition, and thus identifying those less likely to respond to bile salt therapy. Based on chemical analysis and scanning electron microscopy, 28 of 42 (67%) gall stones retrieved at surgery were potentially insoluble. Microscopic examination of duodenal bile correctly identified 21 (75%) of them: it predicted all four (100%) pigment stones, three of six (50%) calcium carbonate containing cholesterol stones, and 14 of 18 (78%) cholesterol stones with pigment shells. It was nearly as reliable as microscopic examination of bile aspirated directly from the gall bladder during surgery (21 (75%) v 23 (82%); p = NS). Furthermore, the presence of cholesterol crystals in duodenal bile was a more sensitive indicator than chemical detection of supersaturation (34 of 38 (89%) v 25 of 35 (71%); p < 0.05) for prediction of cholesterol gall stones. Microscopic examination of duodenal bile, if used as a screening test, could help to exclude potential non-responders and thereby improve considerably the results of oral bile salt treatment for gall stone dissolution.

Gallstones during octreotide therapy

Gallbladder stones (GBS) are found in up to 50% of patients receiving octreotide, but the reported prevalence of cholecystolithiasis in patients treated with octreotide is variable and little is known about gallstone incidence, composition, pathogenetic mechanisms, dissolvability, and primary prevention. Octreotide treatment apart, in industrialised societies most GBS are mixed in composition, cholesterol-rich (arbitrarily greater than 70% cholesterol by weight), radiolucent (70%), and, given a patent cystic duct (70%), dissolvable in bile rendered unsaturated in cholesterol by oral ursodeoxycholic (UDCA) +/- chenodeoxycholic (CDCA) acid treatment. They form when (1) GB bile becomes supersaturated with cholesterol (as the molar ratio of cholesterol to phospholipids in biliary vesicles approaches 1:1, the vesicles become unstable); (2) there is an imbalance between pro- and anti-nucleating factors, which favors cholesterol crystal precipitation; and (3) there is stasis within the GB as a result of altered motor function and/or excess mucus that traps the crystals. These changes may be associated with altered (4) biliary bile acid composition (more DCA and less CDCA than normal), and/or (5) phospholipid fatty acid composition (arachidonyl-rich lecithin acting as a substrate for mucosal prostaglandin synthesis which, in turn, may influence both gallbladder motility, and mucus glycoprotein synthesis and secretion). During octreotide treatment, meal-stimulated cholecystokinin (CCK) release is impaired leading to GB hypomotility, but little is known about the effects of octreotide on biliary cholesterol saturation, crystal nucleation time, mucus glycoprotein concentration, bile acid or phospholipid fatty acid composition. Most, but not all, reports suggest that the prevalence of GBS in octreotide-treated patients is considerably greater than that in age-, sex-, and weight-matched controls, but proof (by pre-treatment and on-treatment ultrasound) that the GBS were absent before, but developed during, therapy is not always available. Furthermore, there are few data on analysis of GBS composition in patients developing stones during treatment, although initial reports suggest that octreotide-associated GBS are also radiolucent, cholesterol-rich, and dissolve with oral bile acid treatment. Maximum GBS attenuation values, measured in Hounsfield Units (HU) by localized computerized tomography scanning of the GB, predict stone composition and dissolvability: GBS with scores of less than 100 HU are cholesterol-rich and dissolve well with oral bile acid treatment. However, preliminary results in 11 acromegalic patients treated with 200 to 600 micrograms octreotide/d for 29 to 68 months show that the HU scores range from 23 to 490 (mean +/- SEM, 116 +/- 41), suggesting that at least four of these 11 patients have non-cholesterol stones.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium and carbonate ion concentrations in gallbladder and hepatic bile

Calcium carbonate is a major component of gallstones, but there are few data on calcium and carbonate (CO3(2-)) concentrations in human bile. Therefore, in patients undergoing cholecystectomy for gallstones, total [CaTOT] and free ionized [Ca2+] calcium concentrations, pH, PCO2, and total [CO2] were measured and [CO3(2-)] was derived in gallbladder and hepatic bile (aspirated anaerobically at surgery or from T tubes). Gallbladder bile had lower pH (6.96 vs. 7.30) and total [CO2] (14.1 vs. 21.6 mmol/L), higher PCO2 (53.8 vs. 40.2 mm Hg), lower [CO3(2-)] (2.52 vs. 6.11 x 10(5) mol/L) and lower [Ca2+] x [CO3(2-)] ion product (1.88 vs. 4.74 x 10(-8) mol/L) than did hepatic bile. Gallbladder bile pH correlated positively with total [CO2], [CO3(2-)], and [Ca2+] x [CO3(2-)] but negatively with PCO2. Patients with surface gallstone calcification had similar gallbladder bile [CaTOT] and [Ca2+] but higher gallbladder bile pH (7.30 vs. 6.90), lower PCO2 (42.9 vs. 57.2 mm Hg), higher [CO3(2-)] (7.29 vs. 1.84 x 10(-5) mol/L), and higher [Ca2+] x [CO3(2-)] ion product [4.73 vs. 1.45 x 10(-8) (mol/L)2] than those with radiolucent gallstones. There were no differences in these parameters between patients with cholesterol stones and those with pigment stones. These data suggest that the human gallbladder acidifies bile by secreting hydrogen ion and that impairment of this secretion is one cause of calcified gallstone formation in humans.

Computed tomography in predicting gall stone solubility: a prospective trial

This prospective study was undertaken to evaluate the correlation between densitometric values of gall stones assessed by computed tomography and the success rate of litholytic therapy in 28 patients eligible for oral treatment. A densitometric study of the stones was performed in all patients before treatment. A cut off point of 60 Hounsfield units (HU) was chosen to divide the subjects into two groups--group 1, 14 patients with low density stones (less than 60 HU) and group 2, 14 patients with high density stones (greater than 60 HU). All patients were treated with ursodeoxycholic acid (8-10 mg/kg/day) for 12 months and followed up by ultrasound. In group 1, dissolution was complete in 50% of the patients and partial in a further 20%. In group 2 patients, complete dissolution was not observed but 33% showed partial dissolution. The number of patients with total dissolution at 12 months was significantly higher in group 1 compared with group 2 (p less than 0.02). These results suggest that computed tomography can be used to select patients with a better likelihood of successful stone dissolution after bile acid therapy.

Gallbladder stones--dissolve, blast, or extract? Laparoscopic cholecystectomy versus 'the rest'

This article reviews selected aspects of the non-surgical/minimally invasive treatments of gallbladder stones (GBS) and discusses briefly the residual role of these treatments in the era of laparoscopic cholecystectomy. In patients with specific, gallstone-related symptoms who wish to retain their 'functioning' gallbladders, there are at least six different management options. They range from rapid but invasive to slow but safe: i) the rotary lithotrite; ii) percutaneous cholecystolithotomy; iii) percutaneous transhepatic or iv) endoscopic retrograde cannulation of the gallbladder followed by instillation (manual or pump-assisted) of contact solvents; v) extracorporeal shock-wave lithotripsy + adjuvant bile acids and; vi) oral bile acids alone. The recommended investigation sequence is i) ultrasound (to diagnose the presence of GBS), followed by ii) oral cholecystography (to assess cystic duct patency, gallbladder anatomy and GBS size, number, lucency, buoyancy, and contour), and iii) regional computed tomography scanning of the gallbladder (to predict stone composition and dissolvability and to plan routes of access to the gallbladder). The decision-making steps are i) choice of some form of active treatment versus no treatment (other than observation); ii) in those with specific symptoms and a patent cystic duct who opt for active treatment, to choose between removing versus retaining the gallbladder; and iii) in those who wish to retain their 'functioning' gallbladder, to offer and select the most appropriate of the alternative options. In conclusion, despite the excellence of laparoscopic cholecystectomy, there remains a place for the non-surgical/minimally invasive approaches in a carefully selected minority of symptomatic GBS patients. Although GBS may recur in approximately 50% of patients, the recurrent stones are often asymptomatic, can be detected 'early' by follow-up ultrasound, and are easily treated. Ultimately, the aim of gallstone research must be to prevent not only recurrent but also primary GBS formation, which would obviate the need for both medical and surgical treatment.

Chemical analysis of gallstones

A new promising treatment for patients with symptomatic cholelithiasis is extracorporeal shock wave lithotripsy. In order to learn how to interpret the computed tomographic (CT) densities of gallstones measured in vivo, our radiologists asked the clinical chemistry laboratory to analyse cholesterol, bilirubin and calcium in gallstones. No reference methods for the analysis of gallstones have been described. A literature search for manageable quantitative methods for these analyses was not successful. Among the different X-ray diffraction, infrared and chemical analyses described, we could find no well documented analyses that have been compared with reference methods or proposed reference methods for serum. This finding prompted us to develop chemical methods for cholesterol, bilirubin and total calcium in gallstones starting from (proposed) reference methods for serum and to investigate the accuracy, imprecision and linearity of these methods.

A practical guide to the nonsurgical treatment of gallstones

Until recently, cholecystectomy was the only treatment available for symptomatic gallstone disease. During the past 20 years, better understanding of the pathogenesis of cholesterol gallstone disease has led to alternative nonsurgical methods for treating gallstones in selected groups of patients. Use of 2 naturally occurring bile acids, chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), was reported in 1972 and 1975, respectively, for successful dissolution of cholesterol gallstones in humans. Both these bile acids act by reducing cholesterol secretion in bile, thus enabling it to solubilise more cholesterol from the stone surface. Micellar solubilisation is involved, together with liquid crystal formation in the case of UDCA. Having been extensively studied in clinical trials to assess efficacy and safety, both these compounds are now available for general use. The efficacy of CDCA can be enhanced by single bedtime dose administration and by taking a low cholesterol diet. Bedtime administration also enhances the effect of a suboptimal dose of UDCA. CDCA induces dose-related diarrhoea and hypertransaminaemia, and UDCA can induce calcification of gallstones, thus rendering them resistant to medical dissolution. A combination of the 2 bile acids at half the recommended dose for each has become an accepted practice for reducing adverse effects, and this may also enhance efficacy. One of the main problems of bile acid therapy is that dissolution of gallstones is a very slow process. Use of extracorporeal shockwave lithotripsy (ESWL) to break the stones into smaller fragments, with concurrent use of bile acids, has been shown to speed dissolution rate and to achieve complete gallstone dissolution in 78% of selected cases within 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Gallstone dissolution

Many methods are available for gallstone dissolution, including oral bile salts; cholesterol solvents such as mono-octanoin or methyl tert-butyl either; and calcium or pigment solvents such as EDTA and polysorbate. Which of these approaches will be appropriate for an individual patient depends on the type of stones; whether they are in the gallbladder or the bile ducts; whether access to the biliary tree is available; the patient's age and general medical condition; and the availability of necessary expertise. In the US, both chenodeoxycholate and ursodeoxycholate are now available. Ursodeoxycholate is more expensive but appears to produce fewer side effects and may be more efficacious. These agents are most effective in thin women with small floating, radiolucent cholesterol stones in a functioning gallbladder. Only about half of the small subset of patients will experience partial or complete dissolution of stones within a year. Stone recurrence and the potential toxicity of long-term therapy are problems with this approach. Therefore, for most patients, cholecystectomy, either in the traditional fashion or using a laparoscopic approach (see article later in this issue by Gadacz et al), is the most cost-effective and perhaps the safest option. Intragallbladder instillation of methyl tert-butyl ether probably will be applicable only to a small subset of patients, and treatment is likely to be followed by a high recurrence rate. In patients with retained common duct cholesterol stones and access to the biliary tree, mono-octanoin therapy is advantageous in that it can be initiated as soon as cholangiography demonstrates no extravasation. In properly selected patients, a 90% success rate with this technique can be expected within 7 days.

Analysis of radiolucent gallstones by computed tomography for in vivo estimation of stone components

Successful oral litholytic and other nonoperative therapies of gallstones require exact determination of the stone components. Since computed tomography (CT) provides highly sensitive measurement of density, we performed a study to evaluate whether CT measurement of stone density allows a prediction of the composition of radiolucent gallstones. Twenty-eight patients presenting with 29 radiolucent gallbladder (n = 17) or common bile duct stones (n = 12) were included. Prior to operative or endoscopic therapy the attenuation values (Hounsfield Units, HU) were assessed in vivo by CT under standardized conditions (Somatom II, 125 KV, 130 mAs). After surgical or endoscopic stone removal the concrements were dehydrated, homogenized and then analysed by infra-red spectroscopy. The previously measured Hounsfield units were not known to the investigator. Eighteen cholesterol and 11 pigment stones could be identified. The attenuation values (Hounsfield units) of cholesterol stones amounting to 28-98 HU (48.7 +/- 4.4 HU) differed significantly (P less than 0.001) from pigment stones (90-120 HU/105.5 +/- 2.8 HU). We conclude that computed tomography provides exact discrimination between cholesterol and non-cholesterol stones in vivo. Since only cholesterol stones can be dissolved by cheno- and ursodeoxycholic acid we recommend measurement of the radiodensity of gallstones by CT prior to any litholytic therapy. Furthermore the prediction of the stone composition facilitates the decision on extracorporeal shock wave lithotripsy and the selection of specific solvents for contact lysis via a nasobiliary probe.

Review article: bile acid therapy

Over the past 3 years there has been a renewed interest in bile acid therapy not only because of the promising results obtained by combining this therapy with extracorporeal shock-wave lithotripsy for rapid gallstone dissolution, but also because of its novel use as a treatment for primary biliary cirrhosis. This article reviews the use of bile acids for both these indications.

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.

Extracorporeal shockwave lithotripsy of gallstones. Possibilities and limitations

Recently extracorporeal shockwave lithotripsy (ESWL) has been introduced as a nonoperative treatment for gallstone disease. Except for lung damage, no significant adverse effects of ESWL of gallbladder stones have been observed in animals. In clinical use ESWL of gallbladder stones is now confined to 15% to 30% of symptomatic patients. To achieve complete stone clearance, ESWL of gallbladder stones must be supplemented by an adjuvant therapy. ESWL of bile duct stones is highly effective and can be considered in patients in whom primary endoscopic or surgical stone removal fails. Second generation lithotriptors allow anesthesia-free (outpatient) treatments, but the clinical experience with most of these ESWL devices is still limited. The likelihood of gallbladder stone recurrence is a major disadvantage of ESWL treatment, which raises the issue of cost-effectiveness. ESWL for cholelithiasis is a promising treatment modality with good short-term and unknown long-term results.

Fragmentation of gallstones using extracorporeal shock waves: an in vitro study

Eighty in vitro experiments were performed with single (n = 51) or multiple (n = 29) gallstones in order to find out which parameters are of prime importance for their disintegration by extracorporeal shock waves. A Dornier lithotripter and an upper limit of 1,500 discharges were employed. Although computed tomography density was significantly lower in cholesterol stones than in the noncholesterol stones (p less than 0.0001) and although the latter were significantly more often radiopaque (p less than 0.0001), we found no clear-cut correlation between the cholesterol content or computed tomography density and the degree of fragmentation of the stones. The most important variable which limited successful disintegration was the total stone volume. In stones with a mean total volume of 0.83 ml +/- 0.25 S.E. (diameter for single stones = 11.5 +/- 0.9 mm), none of the fragments exceeded 2 mm, whereas in stones with a mean volume of 3.6 ml +/- 0.64 (diameter = 17.2 +/- 1.5 mm) at least one fragment larger than 2 mm remained (p less than 0.002). Under the in vitro conditions, fragmentation was similar in multiple and solitary stones, provided the volume of the stones was comparable. These data show that, in general, the number and size of the stones, i.e. their total volume, and much less significantly their chemical composition are the major determinants of fragmentation by extracorporeal shock waves.

Piezo-ceramic lithotripsy of gallbladder stones: initial experience in 38 patients

The efficacy, safety, and side-effects of a piezo-ceramic system for extracorporeal shock-wave lithotripsy of gallbladder stones were assessed in the first 38 patients treated. Gallstone fragmentation was achieved in 34 patients; 25 required more than 1 treatment session (range 1-5). Extracorporeal shock-wave lithotripsy, conducted without sedation, analgesia, or anaesthesia, was well tolerated by all patients; no patient reported pain or discomfort either during or after the procedure. Side-effects were negligible: transient microscopic haematuria in 2 patients, transiently abnormal liver function tests in 1, and short-lived cutaneous petechiae in 4. Initial experience shows that lithotripsy with this system is effective, safe, and well tolerated.

Agents for gallstone dissolution

Numerous methods are presently available for gallstone dissolution, including oral bile salts; cholesterol solvents such as mono-octanoin and methyl tert-butyl ether; calcium or pigment solvents such as EDTA and polysorbate; mechanical extraction techniques through a T-tube tract or after endoscopic sphincterotomy; or fragmentation methods such as ultrasonography or electrohydraulic lithotripsy, lasers, and extracorporeal shock waves. Which, if any, of these methods will be appropriate for an individual patient depends on the type of stones, whether they are in the gallbladder or bile ducts, whether access to the biliary tree is available, the patient's age and general medical condition, and the availability of expert radiologists, endoscopists, and newer equipment. In the United States, the only available oral bile salt for cholesterol gallstone dissolution is chenodeoxycholate. Ursodeoxycholate, which is more rapid and less toxic, has not been approved by the Federal Drug Administration. These agents are most effective in thin women with small, floating, radiolucent cholesterol gallstones in a functioning gallbladder. Only about half of this small subset of patients, however, will experience partial or complete dissolution of stones in 6 to 12 months. Moreover, recurrence is very likely, and the potential toxicity of long-term therapy is unknown. Thus, for most patients, cholecystectomy remains the most cost-effective and, perhaps, safest option. Intragallbladder instillation of methyl tert-butyl ether and extracorporeal shock wave therapy are also likely to be applicable to only small subsets of patients and to be associated with high recurrence rates. In patients with retained ductal cholesterol stones and access to the biliary tree, mono-octanoin therapy is advantageous in that it can be begun as soon as cholangiography demonstrates no extravasation. In properly selected patients, a 90 percent success rate with mono-octanoin infusion can be expected within a week. Radiologic or endoscopic extraction techniques require maturation of a relatively straight T-tube tract but are not dependent on the type of stone. In the hands of experts, these techniques are highly successful. In postcholecystectomy patients without access to the biliary tree, endoscopic sphincterotomy has become the preferred method of management and can be expected to succeed in more than 90 percent of patients. At this point, the exact role for ultrasonic or electrohydraulic lithotripsy and lasers is unknown. However, these techniques may be applicable in the future in patients with retained bile duct stones in whom extraction and infusion techniques have failed.

Cholesterol and pigment gallstones in northern India. A prospective analysis

Two hundred one consecutive patients with gallstone disease who had undergone cholecystectomy were analyzed to determine the relative frequency of occurrence of cholesterol and pigment gallstones and to identify distinguishing features of the two stone types. Cholesterol stones (CS) formed the majority (94%) of gallstones. There were no distinctive clinical, biochemical, or radiological features of CS or pigment stones (PS). However, CS were found significantly more often than PS (P less than 0.05) in multiparous women leading a sedentary life-style. Although multiplicity of gallstones was somewhat commoner with CS (P less than 0.05) and radiopacity with PS (P less than 0.05) as compared with the other stone type, these differences were certainly not discriminatory between CS and PS.

Utility of biliary microscopy for the prediction of the chemical composition of gallstones and the outcome of dissolution therapy with ursodeoxycholic acid

To learn whether microcrystalline solids in bile could predict gallstone composition, the findings determined by polarizing microscopy of gallbladder bile were related to stone type at cholecystectomy in 53 patients. Cholesterol crystals were present in 36 of 39 cholesterol stone bile and absent in 12 of 14 bile from non-cholesterol stones. Fifteen cholesterol stones (eight radiopaque) contained calcium carbonate, and characteristic vaterite microspheroliths were observed in 53% of their bile. In another study, crystals in basal duodenal bile were related to the outcome of gallstone dissolution treatment with ursodeoxycholic acid, 10 mg/kg X day. In 39 patients treated for 1 yr, efficacy (complete gallstone dissolution) was 41% overall and 52% in patients with stones less than or equal to 10 mm in diameter. In connection with the findings of biliary microscopy, efficacy was 93% in 14 patients with cholesterol crystals in bile, and 27% in 11 patients with microspheroliths in bile. Cholecystectomies in 9 patients with dissolution failure revealed 4 cases of non-cholesterol stones and 5 cases (including 3 with on-therapy calcification) of calcium carbonate-rich cholesterol stones with a surface/interior mineral ratio greater than 3. The results confirm that cholesterol crystals in bile are a sensitive measure of cholesterol gallstones. They also show that vaterite microspheroliths in bile indicate the presence of calcium carbonate in gallstones. Both findings suggest that biliary crystals reflect gallstone composition, and it is demonstrated that this information is useful in predicting the success or failure of cholelitholysis with ursodeoxycholic acid. Finally, the data show that radiologically undetectable stone calcification reduces the probability of dissolution, and that the calcified structures appearing in some stones during treatment are composed of calcium carbonate.

Effect of obesity and weight reduction on biliary cholesterol saturation and the response to chenodeoxycholic acid

Biliary cholesterol saturation indices (SI's) were measured in fasting duodenal bile from (i) obese and non-obese individuals with and without cholesterol gallstones, (ii) obese individuals undergoing weight reduction and (iii) obese gallstone patients receiving chenodeoxycholic acid (CDCA) therapy. Biliary lipid secretion rates were also measured in three obese subjects before and during 11 days starvation. The mean SI in fifteen non-obese controls (0.89 +/- SEM 0.06) was significantly lower than that in the twenty-four obese without (1.14 +/- 0.07; P less than 0.01), and in the twenty-nine non-obese with gallstones (1.30 +/- 0.05; P less than 0.001) while in sixteen obese gallstone patients, the mean SI of 1.55 +/- 0.06 was significantly higher than that seen in the other three groups (P less than 0.01-0.001). Although fifteen obese subjects lost 15% of their initial body weight during dieting, this did not change their SI's consistently. However in three obese individuals, total starvation did reduce the SI's and significantly lowered the biliary cholesterol secretion rate. Ten obese gallstone patients responded to 15.8 +/- 0.3 mg CDCA kg-1 day-1 by developing unsaturated fasting duodenal bile (SI 0.89 +/- 0.04). A further increase in CDCA dose to 19.0 +/- 0.7 mg kg-1 day-1, as a result of reducing body weight, was more effective in lowering SI's (0.75 +/- 0.06, range 0.51-1.0) than that achieved by increasing the dose to 18.9 +/- 0.46 mg kg-1 day-1 through more capsules per day (SI 0.89 +/- 0.03, range 0.67-1.25). These studies show that (i) biliary cholesterol SI's are greater when obesity and gallstones occur together than in either obesity or gallstones alone, and (ii) although weight loss in obese individuals does not consistently alter biliary cholesterol SI's, it may be beneficial in obese patients receiving CDCA therapy for gallstone dissolution.

An X-ray diffraction study of the crystalline composition of gallstones

The crystalline composition of gallstones removed from 30 patients from southwestern Finland was determined by the X-ray powder method. A total of eight crystalline compounds, varying from one to four per stone, were identified. Anhydrous cholesterol was by far the most abundant compound, occurring in 29 patients (97%), and calcium salts occurred in half the material studied. The stones could be classified on the basis of crystalline composition: pure cholesterol stones (40%), stones of cholesterol and calcium carbonate (37%), stones of cholesterol and sodium chloride or/and calcium palmitate (20%), and a stone of apatite and calcium carbonate (3%). The average amount of crystalline components per stone was as follows: cholesterols, 82%; calcium carbonates, 14%; and the rest, apatite, calcium palmitate, and sodium chloride. The crystalline composition of the stones related to the sex and age of the patients indicated several trends, including the occurrence of calcium carbonates in the stones of patients over 50 years of age and their simultaneous occurrence in small stones and with the cholesterols. Calcium palmitate was also more frequently present in the calculi of male patients.

The Sunnybrook Gallstone Study: a double-blind controlled trial of chenodeoxycholic acid for gallstone dissolution

The Sunnybrook Gallstone Study was a randomized, double-blind, controlled trial of chenodeoxycholic acid treatment over 2 years in 160 patients with radiolucent gallstones. Sixty-four patients received 750 mg daily, 53 received 375 mg daily and 43 received placebo. Total dissolution of gallstones occurred in 10.9% of patients on 750 mg daily, 13.2% of those on 375 mg daily and in no patient on placebo. The drug was tolerated well. Diarrhea severe enough to cause withdrawal from the study occurred in two patients. No patient developed clinically significant hepatotoxicity. Serum cholesterol rose 10% or more above baseline after 2 years in 33% of patients treated with chenodeoxycholic acid and in 30% of those on placebo. Cholecystectomy was performed in 10.9% of patients on 750 mg daily, 17% on 375 mg daily and 13.6% on placebo. Chenodeoxycholic acid given at these doses dissolved radiolucent gallstones safely but the efficacy was limited.

Management of stones in the biliary tree

Images

Chemical and physical properties of gall stones in South Australia: implications for dissolution treatment

Of 406 consecutive patients with gall-bladder stones, 387 were treated by cholecystectomy and 19 were treated with chenodeoxycholic acid. The gall stones found in 356 of the 387 patients at operation were analysed chemically for cholesterol and calcium, physically for number, size, and mass, and radiologically before cholecystectomy for stone lucency. Gall stones rich in cholesterol (greater than 80% by weight) were present in 75% of patients, while pigment stones (less than 25% cholesterol) were found in 12% of patients. Out of the 406 gall-stone patients, 77 (19%) had functioning gall bladders which contained radiolucent stones 1.5 cm or less in diameter, thereby fulfilling the criteria which are used by most clinicians in selecting patients for dissolution therapy of cholesterol gall stones. The stones of 61 of these patients were available for chemical analysis and 52 (85%) were rich in cholesterol. Using the more stringent criterion for stone size of 1 cm or less in diameter, only 11% of patients had stones suitable for dissolution treatment. Taking into account other factors such as lack of compliance with treatment, obesity, and calcium salts in gall stones, it appears that no more than 10% of gall-stone patients presenting to a general hospital could be successfully treated with chenodeoxycholic acid.

Factors affecting gall-stone dissolution rate during chenic acid therapy

Gall-stone dissolution rate was measured in 52 patients with radiolucent gall stones in a functioning gall bladder receiving chenic acid 15 mg/kg/day. Percentage reduction in gall-stone area at six months was inversely related to initial gall-stone diameter (n = 52; r = -0.53; p less than 0.001), and to cholesterol saturation index of fasting gall-bladder bile during treatment (n = 28; r = -0.61; p less than 0.001). The duration of treatment required for complete dissolution was directly related to initial gall-stone diameter (r = 0.47; p less than 0.02). We conclude that the rate of gall-stone dissolution depends not only on gall-stone size but also on the degree of unsaturation of gall-bladder bile achieved during chenic acid treatment.

Gallstone dissolution rate during chenic acid therapy. Effect of bedtime administration plus low cholesterol diet

We have studied the dissolution rate of radiolucent gallstones from validated measurements of gallstone area derived from standardized oral cholecystography in 48 patients receiving chenodeoxycholic (chenic) acid, 15 mg/kg/day. Patients were matched in pairs according to gallstone size and randomly allocated to one of two treatment groups. Group A was given chenic acid in three divided doses at mealtimes with an unrestricted diet (the conventional regimen), and group B was given bedtime chenic acid with a low cholesterol diet. In the 24 matched pairs, the mean reduction in gallstone area at 6 months on regimen A was 36% and on B 60%. Median reductions in area were 20% and 57%, respectively (P less than 0.02). Of these matched pairs, 20 were followed at 6 month intervals for 42 months. There was a significant correlation between percentage reduction in gallstone area at 6 months and length of treatment necessary for complete dissolution (P less than 0.001). Fifty percent achieved complete dissolution by 30 months on regimen A, and by 12 months on regimen B (NS). We conclude that gallstone dissolution rate during chenic acid treatment is approximately doubled by bedtime administration plus a low cholesterol diet, thus reducing the duration and cost of treatment.

Study of the sensitivity and specificity of computerized tomography in the detection of calcified gallstones which appears radiolucent by conventional roentgenography

Radiolucent gallstones frequently contain significant calcium deposits. Their detection is important in the evaluation of patients for medical gallstone dissolution treatment. The sensitivity and specificity of computerized tomography (CT) in detecting calcium was studied in 20 patients with radiolucent and in 3 with radiopaque gallstones. Although the sensitivity of the CT scan was somewhat higher than that of conventional radiography -- 46% versus 23%, respectively, for a calcium content of at least 4% -- the CT scan was negative in 4 out of 6 patients in whom the percentage of calcium in the gallstones ranged between 10 and 100. The CT scan was specific: there were no false positive results. The results of the CT scan were not related to the amount or type of calcium salt present. The study shows that the presently used CT scan of the gallbladder is not sensitive enough to select gallstone patients for medical dissolution treatment.