Possible role of a defect in hepatic bilirubin glucuronidation in the initiation of cholesterol gallstones

Role of the Free Radicals in Mechanisms of Gallstone Formation: An EPR Study

The mechanism of gallstone formation is not well understood. Abnormal regulation of hepatic cholesterol, bile acid synthesis or esterification, deposition of cholesterol monohydrate crystals and gall bladder dysfunction are thought to be the principal metabolic aberrations that may cause gallstone formation. One plausible mechanism leading to these abnormalities is the role of free radicals, whose presence can be investigated using Electron Paramagnetic Resonance (EPR). Surgically removed gall bladder stones were used to obtain purified bilirubin, which was irradiated in vitro with visible light and measured with EPR in the presence of and without oxygen. EPR detected oxidized bilirubin free radical (BFR) (g = 2.003, ΔH = 1.0 mTl) in the gallstones. In vitro exposure of bilirubin to visible light in the presence of oxygen induced BFR formation; its intensity was radiation time dependent and decreased under the influence of β-carotene; irradiation in a vacuum did not generate BFRs. These results indicate the important role of oxidative processes (oxidation of bilirubin) in the gallstone formation. In oxidative stress, bilirubin acting as a second type photosensitizer undergoes rapid oxidation and free radical polymerization that plays an important role in the nucleation and deposition of gallstones.

Quantitative assessment of the multiple processes responsible for bilirubin homeostasis in health and disease

Serum bilirubin measurements are commonly obtained for the evaluation of ill patients and to screen for liver disease in routine physical exams. An enormous research effort has identified the multiple mechanisms involved in the production and metabolism of conjugated (CB) and unconjugated bilirubin (UB). While the qualitative effects of these mechanisms are well understood, their expected quantitative influence on serum bilirubin homeostasis has received less attention. In this review, each of the steps involved in bilirubin production, metabolism, hepatic cell uptake, and excretion is quantitatively examined. We then attempt to predict the expected effect of normal and defective function on serum UB and CB levels in health and disease states including hemolysis, extra- and intrahepatic cholestasis, hepatocellular diseases (eg, cirrhosis, hepatitis), and various congenital defects in bilirubin conjugation and secretion (eg, Gilbert's, Dubin-Johnson, Crigler-Najjar, Rotor syndromes). Novel aspects of this review include: 1) quantitative estimates of the free and total UB and CB in the plasma, hepatocyte, and bile; 2) detailed discussion of the important implications of the recently recognized role of the hepatic OATP transporters in the maintenance of CB homeostasis; 3) discussion of the differences between the standard diazo assay versus chromatographic measurement of CB and UB; 4) pharmacokinetic implications of the extremely high-affinity albumin binding of UB; 5) role of the enterohepatic circulation in physiologic jaundice of newborn and fasting hyperbilirubinemia; and 6) insights concerning the clinical interpretation of bilirubin measurements.

Genetics of biliary lithiasis from an ethnic perspective

Gallstone disease represents one of the most common gastroenterological disorders worldwide. Gallstones affect over 15% of adults in Europe and 25-30% of Hispanic populations in Central and South America. The heritability of gallstones varies considerably according to ethnicity, with Native Americans and Hispanics with Amerindian admixture being the most susceptible populations. Genetic factors have been shown to account for 25-30% of total gallstone risk in Europe, however, in Hispanic populations, this risk percentage may increase to 45-65%. Recent genome-wide association and candidate gene studies have identified common polymorphisms in enterohepatic transporters (ABCG5/8, SLC10A2) and the Gilbert syndrome UGT1A1 variant as genetic determinants of gallstone formation. Together, these polymorphisms cover a significant proportion of the previously predicted genetic background of gallstones in European populations. New lithogenic genes need to be discovered in future studies in high-risk populations. In this review, we address the latest developments in the genetic analysis of gallstones and discuss the ethnic background of this condition in European, Central and South American and Asian populations.

Incidence of congenital hemolytic anemias in young cholelithiasis patients

AIM: To clarify the incidence of congenital hemolytic anemias (CHA) in young cholelithiasis patients and to determine a possible screening test based on the results.

METHODS: Young cholelithiasis patients (< 35 years) were invited to our outpatient clinic. Participants were asked for comorbidities and family history. The number of gallstones were recorded. Blood samples were obtained to perform a complete blood count, standard Wright-Giemsa staining, reticulocyte count, hemoglobin (Hb) electrophoresis, serum lactate dehydrogenase and bilirubin levels, and lipid profile.

RESULTS: Of 3226 cholecystectomy patients, 199 were under 35 years, and 190 with no diagnosis of CHA were invited to take part in the study. Fifty three patients consented to the study. The median age was 29 years (range, 17-35 years), 5 were male and 48 were female. Twelve patients (22.6%) were diagnosed as thalassemia trait and/or ıron-deficiency anemia. Hb levels were significantly lower (P = 0.046), and mean corpuscular volume (MCV) and hematocrit levels were slightly lower (P = 0.072 and 0.082, respectively) than normal. There was also a significantly lower number of gallstones with the diagnosis (P = 0.007).

CONCLUSION: In endemic regions, for young cholelithiasis patients (age under 35) with 2-5 gallstones, the clinician/surgeon should pay attention to MCV and Hb levels as indicative of CHA.

Cholelithiasis in thalassemia major

OBJECTIVES

Aim of this study was to evaluate prevalence and characteristics of cholelithiasis in a large population of patients with thalassemia major (TM).

METHODS

Data from 858 consecutive patients with transfusion-dependent thalassemia at five major Italian centers were analyzed. In these centers, a complete abdomen ultrasonography is performed yearly after the beginning of the transfusion regimen. The role of co-inheriting Gilbert's syndrome genotype was investigated studying the promoter region of the UGT1-A1 gene by automated sequencing.

RESULTS

Thirty percent of TM patients had gallstones. The Gilbert's genotype [homozygosity for (TA)(7) motif at UGT1A promoter gene], influenced both the prevalence of cholelithiasis and the age at which it developed.

CONCLUSIONS

Cholelithiasis has a remarkable frequency and precocity in patients with TM and especially in those with (TA)(7)/(TA)(7) UGT1-A1 genotype. An early biliary ultrasonography is recommended from childhood and a closer follow-up in patients with thalassemia and associated Gilbert's syndrome may be indicated.

UGT1A1 promoter polymorphisms and the development of hyperbilirubinemia and gallbladder disease in children with sickle cell anemia

Genetic modifiers contribute to phenotypic variability in patients with sickle cell anemia (SCA). The influence of the bilirubin UDP-glucuronosyltransferase (UGT) 1A1 (TA)(n)TAA promoter polymorphism on bilirubin levels and gallbladder disease in SCA was examined using prospectively collected data from the Cooperative Study of Sickle Cell Disease. A total of 324 children with HbSS (median age 6.9 years) had UGT1A1 genotyping; 243 (75%) had common (TA)(6) or (TA)(7) alleles, whereas 81 (25.0%) had variant (TA)(5) or (TA)(8) alleles. The UGT1A1 genotype significantly influenced average bilirubin levels for the common alleles: 6/6 genotype = 2.36 +/- 1.13 mg/dL, 6/7 genotype = 2.90 +/- 1.54 mg/dL, and 7/7 genotype = 4.24 +/- 2.11 mg/dL (P < 0.0001). Thirty-nine percent of children with the 7/7 genotype had documented gallbladder disease, compared with 18.2% with the 6/7 genotype and only 9.9% with the wildtype 6/6 UGT1A1 genotype (P = 0.001). To analyze the (TA)(5) and (TA)(8) variant alleles, three groups were generated, showing increasing bilirubin levels with increasing TA repeats and age. Group 3 (genotypes 6/8, 7/7, and 7/8) had a significantly greater rate of bilirubin change than Groups 1 (genotypes 5/6, 5/7, and 6/6) or 2 (genotype 6/7). These results validate previous smaller studies and confirm that the UGT1A1 promoter polymorphism exerts a powerful influence on bilirubin levels and the development of gallbladder disease in children with SCA. UGT1A1 genotyping should be considered as a screening tool for predicting children most likely to develop gallbladder disease at a young age.

Determination of chemical composition of gall bladder stones: Basis for treatment strategies in patients from Yaounde, Cameroon

AIM: Gallstone disease is increasing in sub-saharan Africa (SSA). In the west, the majority of stones can be dissolved with bile salts, since the major component is cholesterol. This medical therapy is expensive and not readily accessible to poor populations of SSA. It was therefore necessary to analyze the chemical composition of biliary stones in a group of patients, so as to make the case for introducing bile salt therapy in SSA.

METHODS: All patients with symptomatic gallstones were recruited in the study. All stones removed during cholecystectomy were sent to Houston for x-ray diffraction analysis. Data on age, sex, serum cholesterol, and the percentage by weight of cholesterol, calcium carbonate, and amorphous material in each stone was entered into a pre-established proforma. Frequencies of the major components of the stones were determined.

RESULTS: Sixteen women and ten men aged between 27 and 73 (mean 44.9) years provided stones for the study. The majority of patients (65.38%) had stones with less than 25% of cholesterol. Amorphous material made up more than 50% and 100% of stones from 16 (61.53%) and 9 (34.61%) patients respectively.

CONCLUSION: Cholesterol is present in small amounts in a minority of gallstones in Yaounde. Dissolution of gallstones with bile salts is unlikely to be successful.

Unconjugated bilirubin in human bile: the nucleating factor in cholesterol cholelithiasis?

AIMS

To investigate the concentrations of bilirubin, bilirubin conjugates, phospholipid, and cholesterol in the gall bladder bile obtained at surgery from patients with and without cholesterol gallstones.

METHODS

Gall bladder bile was collected during surgery, by puncture, from 20 patients with gallstones undergoing routine cholecystectomy and from eight patients with normal liver blood tests. Concentrations of bilirubin, bilirubin conjugates, phospholipid, and cholesterol were measured using standard procedures.

RESULTS

The proportion of total bilirubin that was unconjugated was significantly higher in the bile from patients with stones than in bile from control patients, whether or not the bile from either group was saturated with cholesterol or not. Indeed, the mean concentration of cholesterol was significantly higher in control bile samples.

CONCLUSION

The presence of stones was more closely related to the proportion of unconjugated bilirubin than to the degree of saturation of bile with cholesterol. Bilirubin and its metabolites probably play an important part in the formation of cholesterol gallstones.

Cholelithiasis and Gilbert's syndrome in homozygous beta-thalassaemia

Cholelithiasis has been reported with a variable incidence in homozygous beta-thalassaemia, the reasons for which have only partially been defined. Disease-associated factors or specific modifier genes may be implicated. We assessed the prevalence of cholelithiasis and the effect of co-inherited Gilbert's syndrome genotype on its development in 261 thalassaemia major (TM) and 35 thalassaemia intermedia (TI) patients. Cholelithiasis was found in 20.3% of TM and in 57.1% of TI patients. Its incidence was higher (P < 0.05) in patients homozygous for the (TA7) motif in the promoter of the UGT1-A1 gene, the genotype associated with Gilbert's syndrome, which seems to be a risk factor for the development of gallstones in TM and TI patients.

Brown pigment stones in the common bile duct: reduced bilirubinate diconjugate in bile

BACKGROUND

Bilirubin is the main component of most common bile duct stones. Normally, almost all bilirubin in bile is conjugated to glucuronic acid or some other sugar moiety. These conjugates are unstable and liable to deconjugation. Unconjugated bilirubin is insoluble and may precipitate as the calcium salt found in brown pigment stones. The pattern of bilirubin conjugates in common duct bile of patients with choledocholithiasis has been unknown.

METHODS

In a clinical series of 55 patients with choledocholithiasis common-duct bile was aspirated, and the bilirubin conjugates analyzed with high-performance liquid chromatography. One stone from each patient was analyzed for cholesterol and bilirubin content to determine stone type.

RESULTS

Sixteen patients had cholesterol stones, 38 patients had brown pigment stones, and 1 patient had a black stone. Patients with pigment stones had a lower percentage of bilirubin diglucuronide (median, 60.3%; interquartile range, 49.7%-67.3%) than patients with cholesterol stones (64.0%; 60.2%-73.3%) (Mann-Whitney, P=0.015). No significant difference was found for the other bilirubin conjugates, total bilirubin, or biliary pH when pigment and cholesterol stone patients were compared. The time of bile sampling in relation to papillotomy and treatment of cholestasis was not associated with the low percentage of bilirubin diglucuronide. The observation of reduced values for bilirubin diglucuronide could not be ascribed to duodenal diverticula or Billroth-II gastric resection.

CONCLUSION

The percentage of the main bilirubinate conjugate, bilirubin diglucuronide, is decreased in the common duct bile of patients with pigmented compared with cholesterol stones.

Coinheritance of Gilbert Syndrome Increases the Risk for Developing Gallstones in Patients With Hereditary Spherocytosis

The precocious formation of bilirubinate gallstones is the most common complication of hereditary spherocytosis (HS), and the prevention of this problem represents a major impetus for splenectomy in many patients with compensated hemolysis. Because Gilbert syndrome has been considered a risk factor for gallstone formation, there are reasons for postulating that the association of this common inherited disorder of hepatic bilirubin metabolism with HS could increase cholelithiasis. To test this hypothesis, 103 children with mild to moderate HS who, from age 1, have undergone a liver and biliary tree ultrasonography every year, were retrospectively examined. The 2-bp (TA) insertion within the promoter of the uridine diphosphate-glucuronosyltransferase gene (UGT1A1), associated with Gilbert syndrome, was screened. The risk of developing gallstones was statistically different among the 3 groups of patients: homozygotes for the normal UGT1A1 allele, heterozygotes, and homozygotes for the allele with the TA insertion. Fitting a Cox regression model, in fact, a statistically significant hazard ratio of 2.19 (95% confidence interval: 1.31 to 3.66) was estimated from one to the next of these genetic classes. The individual proneness to form gallstones from TA insertion in the TATA-box of the UGT1A1 promoter should be considered during the follow-up of patients with HS. Although patients with HS were the only ones studied, extrapolating these data to patients who have different forms of inherited (eg, thalassemia, intraerythrocytic enzymatic deficiency) or acquired (eg, autoimmune hemolytic anemia, hemolysis from mechanical heart valve replacement) chronic hemolysis can be warranted.

Short-term fasting increases biliary calcium and bilirubin

Fasting has been associated clinically with the development of gallbladder sludge and pigment gallstones, both of which are composed primarily of calcium bilirubinate. Although fasting has been demonstrated to increase the cholesterol saturation of bile, its effect on biliary calcium and bilirubin has not been investigated. We, therefore, tested the hypothesis that short-term fasting would increase gallbladder bile calcium and bilirubin levels. Fifteen prairie dogs were studied. Seven animals were not fasted, whereas eight were fasted for 16 hr prior to acute experiments. Gallbladder and hepatic bile samples were obtained and analyzed for calcium, bilirubin, pH, and biliary lipids. Gallbladder bile ionized calcium levels were significantly increased in fasted animals (1.7 +/- 0.2 mM) compared to those in nonfasted animals (1.1 +/- 0.1 mM). Similarly, total calcium (4.3 +/- 0.5 mM vs 2.3 +/- 0.3 mM), total bilirubin (63 +/- 12 microM vs 29 +/- 8 microM), and bilirubin monoglucuronide (58 +/- 10 microM vs 22 +/- 8 microM) were significantly increased in the fasted group. Fasted animals were also noted to have an increased biliary cholesterol saturation index (0.57 +/- 0.04 vs 0.36 +/- 0.03) and decreased biliary pH (6.9 +/- 0.1 vs 7.6 +/- 0.1). These data indicate that in the prairie dog short-term fasting results in significant alterations in gallbladder bile composition. The increased concentrations of gallbladder calcium and bilirubin observed in these experiments may account, in part, for the formation of pigment gallstones and gallbladder sludge seen clinically with prolonged fasting.

Bacteria and gallstone nucleation

This preliminary study reports for the first time that there might be a possible association between bacteria and the aetiology of some cholesterol calculi. The gall-bladder biles from 225 cholecystectomy patients underwent bacteriological and microscopic study. Cholesterol calculi from 13 patients (10.2%) were observed to be associated with gall-bladder bile profusely infected with at least one bacterial species that was shown to possess beta-glucuronidase activity, an enzyme that is thought to promote calcium bilirubinate precipitation in bile. Concomitantly, the associated gall-bladder bile was 'high' in calcium bilirubinate precipitation and the precipitate was also detected in the centre of the gallstones. Moreover, in approximately half of these patients (six of 13), the cholesterol gallstones' nuclear areas also contained calcium palmitate, which is also thought to be due to bacterial activity. The results also support the hypothesis that bacteria with active beta-glucuronidase (for example, Escherichia coli) can significantly influence the aetiology of brown pigment gallstones. In contrast, bacteria were observed to have no role in black pigment gallstone formation, as their associated gall-bladder biles were always observed to be sterile.

Sensitivity and specificity of microscopic examination of gallbladder bile for gallstone recognition and identification

During cholecystectomy, gallbladder bile and gallstones were obtained from 77 patients and gallbladder bile was obtained from 39 patients free of stones (11 patients had biliary stenosis). According to their chemical composition, gallstones were classified as cholesterol (n = 46) or pigment (n = 31) stones. In patients with gallstones (a) cholesterol crystals better helped to identify cholesterol gallstones (sensitivity, 87%; specificity, 97%; positive predictive value, 97%) than did an abnormal cholesterol saturation index of bile (sensitivity, 93%; specificity, 48%; positive predictive value, 73%); (b) the presence of cholesterol crystals was significantly related to the cholesterol content of gallstones and the bile cholesterol saturation index; and (c) bilirubinate crystals, when present alone (without cholesterol crystals), were good predictors of pigment gallstones (sensitivity, 71%; specificity, 93%; positive predictive value, 88%). In the absence of stones, bilirubinate crystals were present in 9 of 28 patients without biliary stenosis (4 with alcoholic cirrhosis and 2 with alcoholic pancreatitis) and 8 of 11 patients with biliary stenosis. In the absence of stones, cholesterol crystals were present in 2 of 28 patients without biliary stenosis and in 4 of 11 patients with biliary stenosis, suggesting that bile stasis can induce cholesterol crystal formation.

Identification and localization of the apoprotein fraction of the bile lipoprotein complex in human gallstones

The anionic polypeptidic fraction is the protein constituent of the bile lipoprotein complex. Double immunodiffusion and sodium dodecyl sulfate polyacrylamide gel electrophoresis studies show that the anionic polypeptidic fraction is present in human gallstones. In terms of weight percentage, this protein accounts for 0.1% +/- 0.087 (n = 6) of the total weight of gallstones. Immunolocalization studies confirm the presence of the anionic polypeptidic fraction in human gallstones and suggest that this protein is preferentially associated with pigmented layers in gallstones. A speculative role for the anionic polypeptidic fraction in cholesterol nucleation is discussed.

Monoconjugated bilirubin is a major component of hemolysis-induced gallstones in mice

The role of bilirubin conjugates in the formation of pigment gallstones is not known. In this study, we completely solubilized and then analyzed by high-performance liquid chromatography specimens of black pigment gallstones from eight nb/nb mice with hereditary hemolytic anemia. Each dried gallstone specimen of about 200 micrograms was dissolved in 5 ml of dimethyl sulfoxide/0.15 M HCI/50 mM disodium-EDTA (8:1:1 by volume) at room temperature. Stone dissolution was complete by 30 min as monitored by the A456 and direct observation, and no oxidative products of bilirubin were observed in the visible spectrum, 350 to 750 nm. By high-performance liquid chromatography, the intact tetrapyrroles were separated as diconjugated and monoconjugated bilirubins; unconjugated bilirubin was resolved as XIII, IX and III alpha-isomers. The isocratic solvent system used was 0.1 M di-n-dodecylamine acetate/0.1 M di-n-octylamine acetate (4:1, v/v) in methanol, pH 7.4, at a flow of 1 ml per min. Diconjugated bilirubin accounted for 6.0 +/- 2.4 molar % (mean +/- S.E.), monoconjugated bilirubin for 37.4 +/- 8.4% and unconjugated bilirubin for 56.3 +/- 8.9% of the solubilized pigments. The IX alpha-isomer represented 96 +/- 1.9% of the unconjugated bilirubin. The presence of bilirubin conjugates in gallstones was confirmed by ethylanthranilate diazotization: the conjugated azodipyrrole in stone had the same retention time as that of conjugated azodipyrrole from rat and mouse bile. A majority of the bilirubin conjugates was sensitive to beta-glucuronidase of liver origin, indicating that the C-1 glucuronide ester was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonbacterial transformation of bilirubin in bile

Bilirubin present in gallstones is mainly in the unconjugated form despite the frequent absence of bacteria in bile. The aim of the present study was to determine if nonbacterial beta-glucuronidase activity and/or nonenzymatic hydrolysis is responsible. Inflammatory cells such as polymorphonuclear leukocytes and lymphocytes appearing with the presence of brown pigment gallstones and inflammation in biliary tract was shown to effect deconjugation of bilirubin conjugates in bile and contribute to their formation in addition to that of bacterial beta-glucuronidase. Gallbladder bile (mean +/- SD, 4.0 +/- 1.6%, N = 29) contained more unconjugated bilirubin than hepatic bile (mean +/- SD, 2.7 +/- 1.1%). In vitro experiments showed the deconjugation to take place during incubation at 37 degrees C without the presence of bacteria. Therefore, transformation of conjugated to unconjugated bilirubin is likely to take place in vivo during the storage in gallbladder, and nonbacterial beta-glucuronidase activity and/or nonenzymatic hydrolysis may be responsible for such transformation.

Properties of human hepatic UDP-glucuronosyltransferases. Relationship to other inducible enzymes in patients with cholestasis

Glucuronidation of 4-nitrophenol, nopol (a monoterpenoid alcohol) and bilirubin, which in the rat, are catalyzed by three different enzymes, has been examined in liver biopsies from patients with various liver diseases, in particular cholestasis. These different activities were not correlated, which strongly suggests that at least three independently regulated forms of UDP-glucuronosyltransferases were present in the microsomes. Non ionic detergents (Triton X100, Emulgen 911) and deoxycholate produced similar activation (more than 2-fold) of the glucuronidation of 4-nitrophenol. Amphipathic substances, such as CHAPS (3-[3-cholamidopropyl-dimethylammonio]-1-propane sulfonate), and lysophosphatidylcholines maximally increased this UDP-glucuronosyltransferase activity, the most potent being oleoyl lysophosphatidylcholine (4-fold increase). Discriminant analysis of the data revealed no correlation between the three different UDP-glucuronosyltransferase activities and the age or sex of the patients. A good correlation was found on multidimensional analysis between form 1 of the enzyme (4-nitrophenol glucuronidation) and, in decreasing order of magnitude, epoxide hydrolase (measured with benzo(a)pyrene-4,5-oxide as substrate), cytochrome P-450, 7-ethoxycoumarin deethylase, aspartate aminotransferase and gamma-glutamyltransferase (r = 0.89); and between Form 3 of the enzyme (bilirubin glucuronidation) and NADPH cytochrome c reductase, alkaline phosphatase, (r = 0.81). These relationships may reflect the differential variation in enzymatic activities in various hepato-biliary diseases.

Human biliary beta-glucuronidase: correlation of its activity with deconjugation of bilirubin in the bile

Total and conjugated bilirubin contents of gall-bladder and hepatic biles before and after 24-h incubation at 37 degrees C and beta-glucuronidase activity of hepatic biles were determined in forty-eight patients divided equally into four groups: no stones or control (C), cholesterol stones (CS), black pigment stones (black PS), and brown pigment stones (brown PS). The percent conjugation of bilirubin is lower in gall-bladder biles and hepatic biles after incubation, particularly in black PS and brown PS, when compared with hepatic biles before incubation. Mean endogenous beta-glucuronidase activities at pH 5.2 were 12.0, 15.5, 44.5 and 147.7 nmol min-1 ml-1 for C, CS, black PS, and Brown PS, respectively, which correlated well with the degree of deconjugation of bilirubin in gall-bladder and hepatic biles and with the rate of deconjugation of hepatic bile incubated at 37 degrees C. Only four biles in brown PS exhibited bacterial enzyme activity. We concluded that though bacterial beta-glucuronidase might be responsible for deconjugation of bilirubin in some patients in brown PS, endogenous biliary beta-glucuronidase could play a key role in the pathogenesis of pigment cholelithiasis.

Chemical composition of common bile duct stones

The common bile duct stones obtained from 148 patients were analysed chemically for cholesterol, calcium and bilirubin. When stones were present in both the common bile duct and gallbladder at the time of surgery, the common duct stones were similar in chemical composition to gallbladder stones in the majority of cases and were predominantly cholesterol-type stones. However, common bile duct stones from patients whose gallbladders had been removed at least one year before the detection of common duct stones contained less cholesterol and more bilirubin than common bile duct stones which were associated with gallbladder stones. Thirty per cent of these stones contained suture material in the centre of the stone. Overall, the results indicate that common bile duct stones are more likely to be pigment type than gallbladder stones, especially if the common duct stones are large, have formed in the duct and become symptomatic less than 12 years after cholecystectomy. Non-absorbable suture material should be avoided in surgery involving the common bile duct.

Application of a rapid and efficient h.p.l.c. method to measure bilirubin and its conjugates from native bile and in model bile systems. Potential use as a tool for kinetic reactions and as an aid in diagnosis of hepatobiliary disease

We have developed an extremely rapid and efficient reverse-phase h.p.l.c. method for the measurement of bilirubin and its conjugates in human bile and in model bile systems. Our method involves the use of a Perkin-Elmer 3 mu C18 column and a methanol/sodium acetate/aq. ammonium acetate buffer system. Three isomers of bilirubin diglucuronide (BDG), two isomers of bilirubin monoglucuronide (BMG), three isomers of unconjugated bilirubin (UCB) and minor conjugates containing glucose and xylose were separated in 12 min. Initial quantification of BDG and BMG was based on the use of the ethyl anthranilate azo derivative of bilirubin (AZO UCB); however, the standard curves for BDG, BMG and UCB were similar enough to permit quantification to be later based on the UCB standard curve only, thereby simplifying the quantification process. Routine direct injection of 6 or 10 microliter of crude undiluted or diluted (1:1) bile sample was sufficient for analysis. The method was helpful in diagnosing biliary-tract obstruction in a newborn and a partial deficiency state of bilirubin conjugation (Crigler-Najjar syndrome) in a 10-year-old male. When the method was applied to biles of patients both with and without gallstones, levels of UCB were less than 2% of total pigment, consistent with previous reports. Because of its speed and efficiency, this method has the potential for a broad range of applications including enzymic, kinetic and bile sample analyses.

Identification of gallbladder mucin-bilirubin complex in human cholesterol gallstone matrix. Effects of reducing agents on in vitro dissolution of matrix and intact gallstones

The goals of this study were to isolate and characterize the nonlipid matrix of human cholesterol gallstones. The lipid portion of gallstones was dissolved in ethanol/ether, leaving an insoluble, granular, brown-black matrix that constituted 12.5% of solitary large stones and 3.5% of multiple small stones. The matrix was partially solubilized by sonication and studied by exclusion gel chromatography and density gradient ultracentrifugation. On Sepharose 2B column chromatography, bile pigment eluted with glycoprotein in the void volume, suggesting the presence of a high molecular weight complex (Mr greater than 2 X 10(6)). The identity of mucin in this complex was confirmed by its typical buoyant density during ultracentrifugation. The major bile pigments in the matrix were identified as bilirubin (84%) and bilirubin monoglucuronide (15%) by thin-layer chromatography. Because of their ability to solubilize mucin-type glycoproteins, we tested the ability of the reducing agents 2-mercaptoethanol (2ME) and N-acetylcysteine (NAcCys) to solubilize gallstone matrix. Both reducing agents caused a two- to threefold enhancement of matrix dissolution after 4 d compared to aqueous buffer alone (P less than 0.01). Sepharose 2B chromatography revealed that 2ME released a high molecular weight mucin-bilirubin complex as well as unbound pigment from the insoluble matrix. We also tested the effect of reducing agents on dissolution of matched cholesterol gallstones by monooctanoin, a cholesterol solvent. Both 2ME and NAcCys significantly accelerated gallstone dissolution in monooctanoin. Matched human cholesterol stones (n = 10) incubated for 4 d in monooctanoin plus either 2ME or NAcCys (1 M final concentration) weighed approximately half as much (P less than 0.01 for each) as stones incubated in monooctanoin alone. This study describes, for the first time, the isolation of a bilirubin-mucin complex in the insoluble matrix of human cholesterol gallstones. The ability of reducing agents to dissolve the matrix and thereby accelerate gallstone dissolution by monooctanoin in vitro may be relevant to gallstone dissolution in humans.

Pigment gallstones of the common bile duct in infancy

Ten infants of less than 6 months of age presented with cholestatic jaundice and gallstones. Jaundice occurred after a lag period, and sepsis was present in three children. Ultrasound examination showed dilatation of intrahepatic and extrahepatic bile ducts in eight patients and detected cholelithiasis in three. Percutaneous transhepatic cholangiography and/or surgery allowed separation of the patients into two groups: (i) six children with lithiasis in the distal common bile duct, and (ii) four children with lithiasis associated with bile duct perforation at the junction between the cystic and common bile ducts with gallstones probably secondary to bile stasis and infection. Surgical treatment was confined to removal of calculi and drainage in eight children; biliary reconstructive surgery was necessary in the other two who had serious biliary duct lesions. No recurrence was observed after 1 to 7 years. The pigmentary nature of cholelithiasis was established by stone morphology in all cases, and by bile and stone analysis in several cases.