Supernatants of irritable bowel syndrome mucosal biopsies impair human colonic smooth muscle contractility.

BACKGROUND: Changes in intestinal motility are likely to contribute to irritable bowel syndrome (IBS) pathophysiology. The aim of the study was to investigate the effects of IBS mucosal supernatants on human colonic muscle contractility. METHODS: Supernatants were obtained from biopsies of 18 IBS patients-nine with constipation (IBS-C) and nine with diarrhea-predominant IBS (IBS-D)-and nine asymptomatic subjects, used as controls. Colonic circular smooth muscle strips or isolated cells (SMC) were exposed to control or IBS supernatants. Spontaneous phasic contractions on strips and morphofunctional parameters on cells were evaluated in basal conditions and in response to acetylcholine (Ach). Incubation with IBS supernatants was also conducted in the presence of antagonists and inhibitors (namely histamine, protease and prostaglandin antagonists, nuclear factor-kappa B inhibitor, catalase, NADPH oxidase inhibitor, and the cAMP- and/or cGMP-cyclase inhibitors). KEY RESULTS: Exposure to IBS-C and IBS-D supernatants induced a significant reduction in basal tone and Ach-elicited contraction of muscle strips and a significant shortening and impairment of Ach contraction of SMCs. The NADPH oxidase inhibitor prevented the effect of supernatants, while the protease antagonist only IBS-C effect. No effect was observed with the other antagonists and inhibitors. Dilution of IBS-D supernatants partially restored the effects only on SMCs, whereas dilution of IBS-C supernatants significantly reverted the effects on muscle strips and Ach-elicited response on SMC. CONCLUSIONS & INFERENCES: Supernatants from mucosal biopsies of IBS patients reduce colonic contractility. The observed impairment was concentration dependent, likely occurring through intracellular oxidative stress damage, involving different neuromotor mechanisms depending on the IBS subtype.

Intra-bolus pressure and esophagogastric gradient, assessed with high-resolution manometry, are associated with acid exposure and proximal migration of refluxate.

Trans-sphincteric pressure gradient (TSPG) seems to play a relevant role in eliciting refluxes during transient lower esophageal sphincter relaxations (TLESRs). Intra-bolus pressure (IBP) is considered to be correlated to esophageal wall tone. We aimed to evaluate the relationship between IBP, TSPG during TLESRs and the dynamic properties of refluxate in gastroesophageal reflux disease. Sixteen non-erosive reflux disease (NERD), 10 erosive disease (ERD) patients and 12 healthy volunteers (HVs), underwent 24-hour impedance-pH monitoring and combined high-resolution manometry-impedance before and 60 minutes. After a meal, ERD patients presented a significantly lower mean IBP (4.7 ± 1.6 mmHg) respect to NERD patients (8.9 ± 2.8 mmHg) and HVs (9.2 ± 3.2 mmHg). NERD patients with physiological abnormal acid exposure time showed a mean IBP (10.4 ± 3.1 mmHg) significantly higher than that in NERD with pathological abnormal acid exposure time (5.1 ± 1.5 mmHg). The TSPG value was significantly higher during TLESRs accompanied by reflux than during TLESRs not associated with reflux, both in patients and in HVs. A significant direct correlation was found between IBP, TSPG and proximal spread of refluxes in patients and in HVs. Gastroesophageal reflux disease patients display different degrees of esophageal distension. An increased compliance of the distal esophagus may accommodate larger volumes of refluxate and likely facilitates the injuries development. Higher TSPG values appear to facilitate the occurrence of refluxes during TLESRs. In patients with NERD, higher TSPG and IBP values favor proximal spread of refluxate and hence may play a relevant role in symptom generation.

Dilated intercellular space diameter as marker of reflux-related mucosal injury in children with chronic cough and gastro-oesophageal reflux disease.

BACKGROUND: The diagnostic corroboration of the relationship between gastro-oesophageal reflux disease (GERD) and chronic cough remains challenging. AIMS: To compare oesophageal mucosal intercellular space diameter (ISD) in children with GERD, children with gastro-oesophageal reflux (GER)-related cough (GrC) and a control group, and to explore the relationship between baseline impedance levels and dilated ISD in children with GER-related cough. METHODS: Forty children with GERD, 15 children with GrC and 12 controls prospectively underwent oesophagogastroduodenoscopy (EGD) with oesophageal biopsies taken 2-3 cm above squamocolumnar junction. ISD were quantified using transmission electron microscopy. Impedance-pH monitoring with evaluation of baseline impedance in the most distal impedance channel was performed in both patient groups. RESULTS: A significant difference in mean ISD values was found between GrC patients (0.9 ± 0.2 µm) and controls (0.5 ± 0.2 µm, P < 0.001), whereas there was no difference between GrC and GERD group (1 ± 0.3 µm, NS). No difference was found in the mean ISD between GrC children with or without pathological oesophageal acid exposure time (1 ± 0.3 vs. 0.9 ± 0.2 µm), and there was no correlation between ISD and any reflux parameter. Finally, there was no correlation between ISD and distal baseline impedance values (r:-0.35; NS). CONCLUSIONS: In children with reflux-related cough, dilated intercellular space diameter appears to be an objective and useful marker of oesophageal mucosal injury regardless of acid exposure, and its evaluation should be considered for those patients where the diagnosis is uncertain. In children with reflux-related cough, baseline impedance levels have no role in identifying reflux-induced oesophageal mucosal ultrastructural changes.

Acid reflux episodes sensitize the esophagus to perception of weakly acidic and mixed reflux in non-erosive reflux disease patients.

BACKGROUND: Non-erosive reflux disease (NERD) patients are more sensitive than erosive esophagitis patients to weakly acidic reflux and to the presence of gas in the refluxate. Intra-esophageal acid perfusion sensitizes esophageal receptors to mechanical and chemical stimuli. METHODS: To establish whether acid sensitization plays a role in the perception of weakly acidic and mixed reflux episodes, 29 NERD patients, responders and 14 non-responders to proton pump inhibitors (PPIs), underwent pH-impedance monitoring. Non-responders repeated the study while on PPIs. To assess the effect of acid exposure on symptom perception, the time period with pH below 4 was measured in 15- and 30-minute time-windows preceding the onset of each reflux episode. KEY RESULTS: Considering weakly acidic and mixed refluxes, both in responder and non-responder patients (off PPIs), the symptomatic refluxes were preceded by a significantly higher cumulative acid exposure than the asymptomatic refluxes. In all patients, following acid reflux, the percentage of symptomatic weakly acidic reflux episodes was significantly higher than that of asymptomatic refluxes. Non-responder patients, off-treatment, were characterized by a lower proportion of weakly acidic reflux and mixed reflux episodes. In the non-responder patients on PPI, only mixed and weakly symptomatic reflux episodes were preceded by a higher cumulative acid exposure. CONCLUSIONS & INFERENCES: In NERD patients, spontaneous acid reflux enhances subsequent reflux perception, regardless of acidity or liquid/mixed composition of episodes; in non-responder patients on PPIs, only the perception of mixed and weakly acidic reflux episodes seems to be mediated by a preceding acid exposure.

Measurement of acid exposure of proximal esophagus: a better tool for diagnosing non-erosive reflux disease.

BACKGROUND: The sensitivity of 24-h pH monitoring is poor in non-erosive reflux disease (NERD). In NERD patients, the proximal extent of acid reflux is one of the main determinants of reflux perception. The present study was aimed to compare the diagnostic accuracy of acid exposure time (AET), at 5 cm above the lower esophageal sphincter, with those at 10 cm and at 3 cm below the upper esophageal sphincter as well as the reproducibility of these parameters. METHODS: A total of 93 consecutive NERD patients, with typical symptoms responsive to proton pump inhibitor treatment, and 40 controls underwent esophageal manometry and multi-channel 24-h pH-test; 13 patients underwent the same study on two occasions. Symptom association probability (SAP) values were evaluated at each esophageal level. KEY RESULTS: The ROC curve indicates that the area under the curve was 0.79 at distal (SE=0.039), 0.87 (SE=0.032) at proximal (P=0.029 vs distal), and 0.85 (SE=0.033) at very proximal esophagus (P =0.148). AET showed a reproducibility of 61% (Kappa 0.22) at distal esophagus, 77% (Kappa 0.45) at proximal and 53% (Kappa 0.05) at very proximal esophagus. The percentage of patients with a positive SAP was not significantly different when assessed at the distal compared with the proximal esophagus. CONCLUSIONS & INFERENCES: In NERD patients, the diagnostic yield of the pH test is significantly improved by the assessment of AET at the proximal esophagus. As this variable seems to be less affected by the day to day variability, it could be considered a reliable and useful diagnostic tool in NERD patients.

Proximal oesophagus: the added value in understanding GORD symptoms.

Over the past decade, the approach to the understanding of the mechanisms involved in the aetiology of gastro-oesophageal reflux disease (GORD) symptoms has changed, and growing evidence now supports the concept that visceral hyper-sensitivity to intra-oesophageal stimuli plays a major role. Among the recent advances, one of the more consistent findings is that the contact of the refluxate, either acidic or weakly acidic, with the proximal oesophageal mucosa, is a main determinant of GORD symptoms, particularly in the large majority of patients affected by non-erosive reflux disease. The data reported in the current issue of Neurogastroenterology and Motility by Bredenoord et al., showing only a small proportion of proximal reflux in patients with Barrett's oesophagus, who are less sensitive to gastro-oesophageal reflux, further support the consistency of this finding in the pathogenesis of symptoms. In the light of these results, we shall look forward, in the management of patients, to approaches aimed at restoring the antireflux barrier, hopefully decreasing the amount of reflux and, in turn, its proximal extent.

Regional oesophageal sensitivity to acid and weakly acidic reflux in patients with non-erosive reflux disease.

The mechanisms underlying symptoms in non-erosive reflux disease (NERD) remain to be elucidated. Non-erosive reflux disease patients appear to be more sensitive to intraluminal stimula than erosive patients, the proximal oesophagus being the most sensitive. In order to assess regional oesophageal changes in reflux acidity and sensitivity to reflux, according either to the acidity or the composition of the refluxate, combined multiple pH and multiple pH-impedance (pH-MII) was performed in 16 NERD patients. According to multiple pH-metry, 29% and 12% of reflux events reached the middle and proximal oesophagus respectively, and 35% and 19% according to conventional pH-MII (P < 0.05). The per-individual analysis confirmed the difference between the two techniques. According to combined distal and proximal pH-MII, approximately 30% of distal acid reflux became weakly acidic at the proximal oesophagus. In all patients, the frequency of symptomatic refluxes, both acid and weakly acidic, was significantly higher at the proximal, compared with distal oesophagus (25 +/- 8%vs 11 +/- 2% for acid reflux and 27 +/- 8%vs 8 +/- 2% for weakly acidic reflux; P < 0.05). Compared with multiple pH-metry, pH-MII shows a higher sensitivity in the detection of proximal reflux. As approximately 30% of acid reflux becomes weakly acidic along the oesophageal body, to better characterize proximal reflux, in clinical practice, combined proximal pH-impedance monitoring should be used. In NERD patients, the proximal oesophagus seems to be more sensitive to both acid and weakly acidic reflux.

Intercellular space diameters of the oesophageal epithelium in NERD patients: head to head comparison between light and electron microscopy analysis.

BACKGROUND: Dilation of intercellular space diameters of oesophageal epithelium detected at transmission electron microscopy morphometry is a marker of tissue injury in non-erosive reflux disease patients. Semi-quantitative evaluation of intercellular space diameters using light microscopy seems to provide promising results. AIM/METHODS: To comparatively evaluate intercellular space diameters in the same patients, by means of morphometry and semi-quantitative analysis, both on light microscopy and transmission electron microscopy microphotographs, biopsies were taken in 29 non-erosive reflux disease patients at distal and proximal oesophagus. Twelve asymptomatic controls underwent the same protocol. RESULTS: Morphometric analysis on transmission electron microscopy microphotographs showed mean intercellular space diameter values of patients, at distal and proximal oesophagus, 3- and 2-fold, respectively, higher than those in controls (p<0.001). On light microscopy microphotographs, mean intercellular space diameter values of patients at distal oesophagus were higher than those in controls, an overlap between patients and controls being observed. The semi-quantitative score was positive in 79% of patients and in 25% of controls at distal esophagus. CONCLUSIONS: Intercellular space diameter morphometric analysis at light microscopy is widely available, allows intercellular space diameter to be quantitatively measured with good sensitivity and specificity and could represent a useful tool in non-erosive reflux disease diagnosis. Despite satisfactory sensitivity, the semi-quantitative score at light microscopy is hampered by much lower specificity than transmission electron microscopy- and light microscopy-morphometry.

Presence of gas in the refluxate enhances reflux perception in non-erosive patients with physiological acid exposure of the oesophagus.

OBJECTIVE: The mechanisms underlying symptoms in gastro-oesophageal reflux disease, particularly in non-erosive reflux disease (NERD), remain to be fully elucidated. Weakly acidic reflux and the presence of gas in the refluxate could be relevant in the pathogenesis of symptoms. METHODS: To assess the relationship between symptoms and weakly acidic, acid and mixed (liquid-gas) reflux, 24 h oesophageal pH-impedance monitoring was performed in 32 NERD and in 20 oesophagitis patients. In 12 NERD patients the study was repeated following 4 weeks treatment with a proton pump inhibitor (PPI). Impedance-pH data were compared with those of 10 asymptomatic controls. Heartburn and acid regurgitation were considered in the analysis of symptoms. RESULTS: 15 NERD patients showed a physiological acid exposure time (pH-negative). Weakly acidic reflux was significantly less frequent in patients (25% (2%), mean (SE)) than in controls (54% (4%), p<0.01). Gas was present in 45-55% of reflux events in patient groups and controls, and decreased following PPI treatment. In NERD pH-negative patients, weakly acidic reflux accounted for 32% (10%) (vs 22% (6%) in NERD pH-positive and 12% (8%) in oesophagitis patients) and mixed reflux for more than two-thirds of all symptom-related refluxes. Multivariate logistic analysis showed that in NERD pH-negative patients, the risk of reflux perception was significantly higher when gas was present in the refluxate (odds ratio, 3.2; 95% CI, 1.2 to 10; p<0.01). CONCLUSIONS: The large majority of symptoms, in all patients, are related to acid reflux. In NERD patients, the presence of gas in the refluxate significantly enhances the probability of reflux perception. These patients are also more sensitive to less acidic reflux than oesophagitis patients.

Effect of oesophagitis on proximal extent of gastro-oesophageal reflux.

Proximal oesophageal acid reflux is increased in gastro-oesophageal reflux disease (GORD) patients with oesophageal and extra-oesophageal symptoms, the latter particularly in presence of oesophagitis. This study was aimed to assess the proximal extent of reflux, both acid and weakly acidic, in GORD patients with and without oesophagitis and to characterize, using an animal model of GORD, the relationship between acute oesophagitis and proximal extent of reflux. Proximal extent of reflux was evaluated during 24-h pH-impedance monitoring in 17 oesophagitis, 27 non-erosive reflux disease (NERD) patients and 10 asymptomatic controls. In five adult cats, reflux events were simulated by intra-oesophageal retrograde injection of a radiopaque solution. Proximal extent of simulated reflux was fluoroscopically assessed before and after inducing acute oesophagitis. The percentage of proximal reflux was 11% in controls, 22% in NERD and 38% in oesophagitis patients (P < 0.05 vs NERD). Weakly acidic reflux showed higher proximal extent in oesophagitis than in NERD patients but it was less proximally propagated than acid reflux. In cats, proximal reflux was significantly increased during acute oesophagitis. Oesophagitis patients show higher proximal extent of reflux, acid and weakly acidic, when compared with NERD patients and controls. In the experimental model, acute oesophagitis favours proximal migration of simulated reflux.

Dilated intercellular spaces and acid reflux at the distal and proximal oesophagus in patients with non-erosive gastro-oesophageal reflux disease.

BACKGROUND: Acid exposure of proximal oesophagus and dilated intercellular space diameters of oesophageal epithelium are relevant in the perception of gastro-oesophageal reflux. AIM: To explain the relationship between gastro-oesophageal reflux disease symptoms, acid exposure and intercellular space diameter along the oesophageal epithelium and to assess time-related variability of intercellular space diameter. METHODS: Thirty-three non-erosive reflux disease (NERD), six erosive oesophagitis patients and 12 asymptomatic controls underwent oesophageal manometry and 24-h dual-channel oesophageal pH-monitoring following endoscopy. Biopsies were taken 5 cm above the LES and 10 cm below the UES, at comparable levels, as pH sensors. A total of 100 intercellular space diameters per patient/control were measured blindly at transmission electron microscopy. In 15 patients, the investigation was repeated after 1 year. RESULTS: In all NERD patients, acid exposure was higher at mid-proximal oesophagus (P < 0.01) and mean intercellular space diameters, at distal and mid-proximal oesophagus, was three- and twofold higher (1.5 and 0.82 micro m, respectively) compared with controls. Intra-patient intercellular space diameter values were stable over time, not overlapping with those of controls. CONCLUSIONS: Dilation of intercellular space diameter occurs along the distal and proximal oesophageal epithelium in NERD patients and could be responsible for the enhanced perception of proximal acid reflux. This finding appears to be time-reproducible and to represent a sensitive, histopathological marker of NERD.

Effect of hiatal hernia on proximal oesophageal acid clearance in gastro-oesophageal reflux disease patients.

BACKGROUND: Proximal acid reflux is common in gastro-oesophageal reflux disease and is a determinant of symptoms. Patients with hiatal hernia complain of more symptoms than those without and are less responsive to proton-pump inhibitors. AIM: To evaluate the role of hiatal hernia on spatiotemporal characteristics of acid reflux. METHODS: Thirty seven consecutive gastro-oesophageal reflux disease patients underwent endoscopy, videofluoroscopy, manometry and multichannel 24-h pH test. Data were compared with those of 15 asymptomatic controls. Multivariate linear regression was used for statistical analysis. RESULTS: At videofluoroscopy, hiatal hernia was found in 16 of 37 patients. The mean size of hiatal hernia was 3.4 cm. Patients showed significantly prolonged acid clearance time, both at proximal and distal oesophagus, compared with controls. Hiatal hernia patients showed a significantly delayed acid clearance, along the oesophageal body, compared with non-hiatal hernia patients. The prolonged acid exposure was maintained during upright and supine position. The presence of hiatal hernia significantly predicted acid clearance delay in the distal and proximal oesophagus [at 10 cm below upper oesophageal sphincter: Delta + 2.5 min (95% confidence interval: 0.4-4.5); P < 0.02]. CONCLUSIONS: The presence of hiatal hernia is a strong predictor of more prolonged proximal oesophageal acid exposure and clearance. Hiatal hernia is likely to play a role in the pathophysiology of gastro-oesophageal reflux disease symptoms, and should be taken into greater consideration in the treatment strategies of the disease.

Effect of endoscopic augmentation of the lower oesophageal sphincter (Gatekeeper reflux repair system) on intraoesophageal dynamic characteristics of acid reflux.

BACKGROUND AND AIMS: Improvements in symptoms following endoscopic procedures for gastro-oesophageal reflux disease (GORD) are seldom supported by normalisation of acid exposure time at the distal oesophagus. However, the distribution of gastric acid within the proximal oesophagus is a main determinant of symptom generation in GORD patients. In this study, our aim was to assess the effect of endoscopic insertion of hydrogel expandable prostheses into the oesophageal submucosa on spatiotemporal characteristics of gastro-oesophageal reflux. METHODS: Oesophageal manometry and multichannel ambulatory 24 hour pH monitoring were carried out in nine patients before and six months after the endoscopic procedure. Dynamic characteristics of gastro-oesophageal reflux in patients were also compared with those in 13 asymptomatic controls. RESULTS: Acid exposure time (AET) at the distal oesophagus decreased from 11.7% (95% confidence interval 6.1-21.8) at baseline to 7.7% (3.7-11.6) at follow up (NS). Of the nine patients, distal AET normalised in three. AET at the middle (7.6% (2.9-12.3)) and proximal (2.4% (0.1-4.8)) oesophagus decreased significantly in all patients (2.4% (0.3-4.5), p <0.01; 1.2% (0.2-2.2), p<0.05 respectively). Proximal extent of acid events significantly decreased in all patients at follow up (37.3% v 9.5%), reaching values observed in asymptomatic controls. Median GORD health related quality of life scores significantly improved from 35.5 at baseline to 9.4. CONCLUSIONS: Despite the lack of a significant improvement in traditional pH variables, endoscopic implant of hydrogel prostheses above the lower oesophageal sphincter significantly decreases proximal spread of acid reflux into oesophageal body. This effect would explain the improvement in symptoms in patients six months after therapy.

Rofecoxib and early relapse of inflammatory bowel disease: an open-label trial.

BACKGROUND: The safety and efficacy of selective cyclo-oxygenase-2 inhibitors in inflammatory bowel disease are under investigation. AIM: To assess, in a prospective, open-label trial, the efficacy and safety of rofecoxib (12.5 mg/day) in inflammatory bowel disease patients and controls. METHODS: The inflammatory bowel disease group included 45 inactive patients (25 Crohn's disease; 20 ulcerative colitis) with associated arthralgia. The control group included 30 dyspeptic patients. The efficacy and safety of rofecoxib were assessed in inflammatory bowel disease patients and controls before and after treatment (range, 3 days to 3 months). RESULTS: In inflammatory bowel disease, nine of the 45 patients (20%) required rofecoxib withdrawal due to gastrointestinal symptoms inducing clinical relapse, which subsided on drug discontinuation. The percentage of patients requiring rofecoxib discontinuation was comparable in patients with Crohn's disease and ulcerative colitis (20% vs. 20%), but was higher in inflammatory bowel disease patients than in controls (20% vs. 3%; P < 0.001). In inflammatory bowel disease, arthralgia relief was reported by 32 patients (71%): complete relief by eight patients (18%) and partial relief by 24 (53%). Thirteen patients (29%) reported no benefit. A comparable percentage of inflammatory bowel disease patients and controls reported arthralgia relief (71% vs. 70%). CONCLUSIONS: Rofecoxib appears to control arthralgia in almost two-thirds of inflammatory bowel disease patients. Side-effects requiring drug discontinuation are observed, however, in almost one-quarter of patients.

Intra-oesophageal distribution and perception of acid reflux in patients with non-erosive gastro-oesophageal reflux disease.

BACKGROUND: The majority of patients with gastro-oesophageal reflux disease do not present with erosive oesophagitis and make up a heterogeneous group. Patients with non-erosive gastro-oesophageal reflux disease are less responsive than patients with oesophagitis to acid-suppressive therapy. AIM: To assess the role of acid reflux in gastro-oesophageal reflux disease symptoms. METHODS: The spatio-temporal characteristics of reflux events were analysed and related to reflux perception in 45 patients with non-erosive gastro-oesophageal reflux disease and 20 patients with erosive oesophagitis. RESULTS: Compared with healthy controls, all patients showed a higher intra-oesophageal proximal spread of acid, which was prominent in patients with non-erosive gastro-oesophageal reflux disease (> 50% of events lasting for 1-2 min). Irrespective of mucosal injury, the risk of reflux perception was very high when acid reached proximal sensors (odds ratio, 7.6; 95% confidence interval, 4.6-12.5), being maximal in patients with non-erosive gastro-oesophageal reflux disease with normal acid exposure time (odds ratio, 11; 95% confidence interval, 5.2-22.3). CONCLUSIONS: Patients with non-erosive gastro-oesophageal reflux disease are characterized by a significantly higher proportion of proximal acid refluxes and a higher sensitivity to short-lasting refluxes when compared with patients with oesophagitis. The highest proximal acid exposure and highest perception occurred in patients with non-erosive gastro-oesophageal reflux disease presenting with a normal pH-metric profile. The assessment of acid distribution and its perception in the oesophageal body can better identify reflux patients who should benefit from acid-suppressive treatment.

Ultrasonographic assessment of gallbladder bile exchanges in healthy subjects and in gallstone patients.

Impaired gallbladder motility may contribute to gallstone pathogenesis by providing time for nucleation and aggregation of cholesterol crystals. Simultaneous scintigraphic-ultrasonographic techniques have been proposed to assess alternating phases of gallbladder emptying and filling. To evaluate patterns of gallbladder motility and of postprandial bile flow by means of a single ultrasonographic technique, 12 healthy volunteers and 20 gallstone patients underwent minute-by-minute gallbladder ultrasonography for 3 h postprandially. Mathematical analysis of volume measurements was used to estimate hepatic and cholecystic bile flux through the gallbladder. Compared to controls, gallstone patients showed greater amounts of unexchanged cholecystic-to-hepatic bile (11% vs. 1%, p <.001) and most of them showed impaired gallbladder washout efficacy. Utrasonographic values of bile exchanges were similar to those derived from scintigraphic-sonographic studies in comparable groups of subjects. This study provides new ultrasonographic variables, which better express gallbladder bile retention in gallstone patients and strongly discriminate gallstone patients from controls.