Morphological alterations in experimental esophagitis. Light microscopic and scanning and transmission electron microscopic study

Effects of dissolved carbon dioxide on the integrity of the rumen epithelium: An agent in the development of ruminal acidosis

The carbon dioxide released and dissolved in rumen fluid may easily permeate across the epithelial cell membrane. Thus, we hypothesized that CO₂ may act as proton carrier and induce epithelial damage under acidotic conditions. Ovine ruminal epithelia were mounted in Ussing chambers under short-circuit conditions. The serosal buffer solution had a constant pH of 7.4 and was gassed either with 100% oxygen or with carbogen (95% O₂ /5% CO₂ ). The mucosal solution was gassed with either 100% oxygen or 100% carbon dioxide. The mucosal pH was lowered stepwise from 6.6 to 5.0 in the presence or absence of short-chain fatty acids (SCFA). The transepithelial conductance (G_t ) as an indicator of epithelial integrity and the short-circuit current (I_sc ) as an indicator of active electrogenic ion transfer were continuously monitored. At an initial mucosal pH of 6.6, there was no significant difference in G_t between the treatment groups. In the absence of both SCFA and CO₂ , G_t remained constant when the mucosal solution was acidified to pH 5.0. In the presence of SCFA, mucosal acidification induced a significant rise in G_t when the solutions were gassed with oxygen. A small increase in G_t was observed in the mucosal presence of CO₂ . However, no difference in final G_t was observed between SCFA-containing and SCFA-free conditions under carbon dioxide gassing during stepwise mucosal acidification. The SCFA+proton-induced increase in G_t could also be minimized by serosal gassing with carbogen. Because of the SCFA+proton-induced changes in G_t and their attenuation by CO₂ , a protective role for mucosally available carbon dioxide may be assumed. We suggest that this effect may be due to the intraepithelial conversion of carbon dioxide to bicarbonate. However, the serosal presence of CO₂ at a physiological concentration may be sufficient to protect the epithelia from SCFA+proton-induced damage for a certain period of time.

In vitro assessment of epithelial electrical resistance in human esophageal and jejunal mucosae and in Caco-2 cell layers

OBJECTIVE

There is a need for a technique allowing studies of human mucosal specimens collected during different clinical conditions. This study elucidates if square wave pulse analysis discriminates between epithelial and transmural electrical resistance and if there is an association with transepithelial permeability of molecular probes.

METHODS

Mucosae from esophagus (surgical resections: n = 14; endoscopic biopsies: n = 15) and jejunum (n = 12) and Caco-2 cell monolayers were investigated in Ussing chambers. Transmural and epithelial electrical resistance were recorded by the use of standardized current pulses. Permeability was assessed using two fluorescein-labeled probes (weight 376 and 4000 Da).

RESULTS

Baseline epithelial electrical resistance was higher in esophageal mucosa (~280 Ω*cm(2)), than in jejunal (~10 Ω*cm(2)) and Caco-2 cells (~140 Ω*cm(2)). The subepithelial contribution to the transmural resistance was higher in jejunal preparations (+88%) and Caco-2 cells (+75%), than in esophageal (+30%). During hypoxia the subepithelial resistance was unchanged, whereas the epithelial resistance decreased significantly in jejunal mucosa and Caco-2 cells. These findings coincided with increased transepithelial probe permeability and signs of disturbed morphology. Esophageal epithelia were resistant to hypoxia. However, exposure to deoxycholic acid and trypsin abolished the esophageal epithelial resistance and increased probe permeability. Endoscopic esophageal biopsies from patients with erosive reflux disease exhibited significantly lower epithelial resistance and higher current than healthy subjects.

CONCLUSION

Square wave pulse analysis in Ussing chambers is suitable for assessment of epithelial electrical resistance that can reflect transepithelial permeability of molecular probes with known size. Moreover, the technique discriminated between healthy and reflux-diseased esophageal mucosal biopsies.

The pathogenesis of Barrett's metaplasia and the progression to esophageal adenocarcinoma

The most important risk factor for the development of Barrett's esophagus is the reflux of both gastric and duodenal contents into the esophagus. The reason why Barrett's metaplasia develops only in a minority of patients suffering from gastroesophageal reflux disease remains unknown.The exact mechanism behind the transition of normal squamous epithelium into specialized columnar epithelium is also unclear. It is likely that stem cells are involved in this metaplastic change, as they are the only permanent residents of the epithelium. Several tumorigenic steps that lead to the underlying genetic instability, which is indispensable in the progression from columnar metaplasia to esophageal adenocarcinoma have been described. This review outlines the process of pathogenesis of Barrett's metaplasia and its progression to esophageal adenocarcinoma.

The role of an alginate suspension on pepsin and bile acids - key aggressors in the gastric refluxate. Does this have implications for the treatment of gastro-oesophageal reflux disease?

OBJECTIVES

During a reflux event the oesophagus is exposed to a heterogeneous mixture of gastric juice components. The role of non-acid components of the refluxate in causing damage to the oesophagus is now well established but no therapeutic option exists to address this.

METHODS

The role of Gaviscon Advance (GA), a raft-forming alginate suspension, in protecting the oesophagus from damage by pepsin and bile acids (aggressors) was investigated using a series of in-vitro models.

KEY FINDINGS

GA was able to dose-dependently inhibit pepsin activity over and above the neutralisation effect of the formulation. This was evident against both protein and collagen substrates using two distinct colorimetric assays. GA was able to retard the diffusion of pepsin and multiple bile acids using a Franz cell model. Using the raft-forming mode of action GA was able to remove both pepsin and multiple bile acids from a simulated reflux event. There was capacity in the GA raft to accommodate aggressors from multiple reflux events.

CONCLUSIONS

GA can specifically remove both pepsin and bile acids from the refluxate, limit their diffusion and affect enzymatic activity of pepsin. There is a role for GA to reduce the damaging potential of the refluxate and thus protect the oesophagus.

Protection of the gastrointestinal tract epithelium against damage from low pH beverages

Extensive consumption of low pH beverages such as citrus juices (pHs 2.3 to 4.3), alcoholic beverages (pHs 2.7 to 4.5), and soft drinks (pHs 2.3 to 4.2) has raised the question of whether exposure of the gastrointestinal (GI) tract to acidic beverages will cause damage to the epithelial lining. To evaluate the potential effects of low pH beverages on the GI tract epithelium, a detailed examination of the literature was undertaken. In some animal models, there is evidence of damage to GI epithelial cells following exposure to low pH beverages; however, in these studies there is no definitive relationship between acidity and the amount or severity of damage. Results from several other studies, conducted in both animals and humans, indicate a lack of adverse effects on epithelial cells. Furthermore, there is no evidence that damage is irreversible. Permanent damage from routine exposure to acidic beverages in humans would not be expected because of repair mechanisms that are available to maintain a healthy epithelium. Additionally, numerous physical, chemical, and biological mechanisms are in place to prevent damage to the epithelial cells. Finally, the safe history of consumption of low pH beverages, including various fruit juices, supports the conclusion that low pH beverage ingestion does not cause damage to the GI epithelium.

Review article: the pathophysiology of gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease (GERD) is a common condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications.

AIM

To review the current knowledge on the underlying factors contributing to GERD, with particular emphasis on the most recent research.

METHODS

Literature searches were conducted in Medline and EMBASE. The abstracts from recent large congresses were also reviewed to ensure coverage of the latest findings.

RESULTS

The pathophysiological factors causing GERD can be split into those inducing greater exposure of the oesophagus to stomach contents, and those that provide increased perception of reflux or increased mucosal damage. Transient lower oesophageal sphincter relaxations, which are likely to be triggered by gastric distension, appear to be a key physiological cause of GERD. Excessive reflux may also be provoked by impaired oesophageal or gastric clearance mechanisms. Pre-epithelial, epithelial and post-epithelial defences all normally protect the oesophagus from injury, and may be compromised in individuals with GERD. Heartburn could also be caused by oesophageal hypersensitivity as a result of visceral neural pathway dysfunction.

CONCLUSION

The pathophysiology of GERD is multifactorial, and abnormalities in the gastro-oesophageal junction, the stomach, the oesophagus and the nervous system may all contribute to this disease state.

Do acid and bile reflux into the esophagus simultaneously? Temporal relationship between duodenogastro-esophageal reflux and esophageal pH

BACKGROUND

Duodenogastro-esophageal reflux (DGER) is an important factor in the pathogenesis of reflux esophagitis. Animal studies have demonstrated that the injurious effect of duodenal juice components depends on pH. The purpose of the present study was to investigate the temporal relationship between DGER and esophageal pH.

METHODS

Seventy-six children with symptoms of gastro-esophageal reflux disease (27 without, 31 with mild, 18 with severe esophagitis) underwent 24 h simultaneous esophageal pH and bilirubin monitoring with Bilitec 2000. The recordings were analyzed for (i) pH at the beginning of DGER episodes; (ii) relative duration of DGER in eight defined pH intervals of 1 pH unit; and (iii) differences in relative duration of DGER between the three groups of children.

RESULTS

DGER episodes most frequently began at pH between 6 and 7. DGER was present in the esophagus across the spectrum of esophageal pH, with the biggest relative duration between pH 3 and 5. However, in children without esophagitis relative duration of DGER was longest between pH 5 and 6, in children with mild esophagitis between pH 4 and 5, while in those with severe esophagitis it was between pH 2 and 4 (P < 0.001).

CONCLUSIONS

DGER appears across the whole esophageal pH spectrum. The more severe the esophagitis, the lower the pH at which DGER occurs, resulting in simultaneous damaging effects of acid and duodenal juice components.

Effects of curcumin on reflux esophagitis in rats

The preventive effect of curcumin, a compound isolated from the rhizome of Curcuma longa, on experimental reflux esophagitis in rats was investigated in order to validate its potential therapeutic use for gastroesophageal reflux disease. Curcumin (20 mg/kg, i.d.), the antioxidative agent dimethyl sulfoxide (DMSO) (1 ml/kg, i.p.) or the proton pump inhibitor lansoprazole (1 mg/kg, i.d.) inhibited the formation of acute acid reflux esophagitis by 52.5, 61.5 and 70.9% respectively. Curcumin alone was not effective in preventing chronic acid reflux esophagitis, but the combination of curcumin and DMSO reduced the mortality rate and the severity of the esophagitis ulcer index to the same extent (56.5%) as did the lansoprazole (53.9%). Intraduodenal administration of curcumin also markedly prevented the formation of acute mixed reflux esophagitis, together with reducing the incidence or the severity of neutrophil infiltration, when compared to a control group. In contrast, lansoprazole tended to increase the severity of all histopathological changes, when compared to either the control or the curcumin-treated group. Aminoguanidine, a specific inducible nitric oxide synthase inhibitor, had no preventive effect against both types of acute reflux esophagitis models, and increased the mortality in the chronic acid reflux esophagitis model. From these results, it is indicated that curcumin can effectively prevent acute reflux esophagitis formation. Although curcumin is less potent than lansoprazole in inhibiting acid reflux esophagitis, it is superior to lansoprazole in inhibiting mixed reflux esophagitis. The antiulcerogenic mechanisms are considered to be closely associated with its antioxidant nature and antiinflammatory property.

Laryngeal epithelial defenses against laryngopharyngeal reflux: investigations of E-cadherin, carbonic anhydrase isoenzyme III, and pepsin

OBJECTIVES

This is the third annual report of an international research network studying the cellular impact of laryngopharyngeal reflux (LPR) on laryngeal epithelium. The objective of this study was to investigate the presence of E-cadherin (epithelial cadherin; the intercellular junctional complex protein) in relation to the presence of (intracellular) pepsin and carbonic anhydrase isoenzyme III (CAIII).

METHODS

Fifty-four laryngeal biopsy specimens from 18 LPR patients were studied by immunohistochemistry and Western blotting for pepsin, E-cadherin, and CAIII. These data were compared to those from normal control subjects analyzed in another research study.

RESULTS

Intracellular pepsin was detected in LPR patients, but not in controls. E-cadherin expression was reduced in patients with LPR. Carbonic anhydrase III expression was not found in the vocal fold or in the majority of samples taken from the ventricle of LPR patients and was inversely associated with E-cadherin membranous expression.

CONCLUSIONS

The findings of depleted E-cadherin and CAIII and the presence of pepsin appear to correlate with LPR. The reduced protective response indicated by the reduced expression of CAIII may play an important role in the disruption of the intercellular barrier associated with the down-regulation of E-cadherin.

Essential role of pepsin in pathogenesis of acid reflux esophagitis in rats

Pepsin, a protease activated by gastric acid, is a component of the refluxate, yet the role of pepsin in the pathogenesis of reflux esophagitis has not been well studied. In the present study, we examined the effect of pepstatin, a specific inhibitor of pepsin, on acid reflux esophagitis. Acid reflux esophagitis was induced in rats by ligating both the pylorus and the forestomach for 3 or 4 hr. Pepstatin, ecabet Na (the anti-ulcer drug), and L-glutamine were administered intragastrically after the ligation. Pepstatin or ecabet Na, given intragastrically, significantly prevented esophageal lesions, even though they did not affect basal acid secretion in pylorus-ligated rats. Pepstatin significantly inhibited pepsin activity in vivo and in vitro, while ecabet Na inhibited this activity in vitro. By contrast, L-glutamine given intragastrically aggravated the lesions in a dose-dependent manner, but even in the presence of L-glutamine the development of esophageal lesions was totally prevented by coadministration of pepstatin or ecabet Na. L-Glutamine increased the pH of gastric contents to approximately 2.0, the optimal pH for the proteolytic activity of pepsin in vitro. In addition, intragastric administration of exogenous pepsin worsened the severity of esophageal damage. These results suggest that pepstatin is highly effective against acid reflux esophagitis, without influencing acid secretion, while L-glutamine aggravated these lesions by increasing the pepsin activity by shifting the intraluminal pH to the optimal pH range for proteolytic action. It is assumed that pepsin plays a major pathogenic role in the development of acid reflux esophagitis.

Inhibition of pepsin activity by alginates in vitro and the effect of epimerization

Alginates are versatile biopolymers used extensively in the food, textile and pharmaceutical industries. One of the major uses is in the treatment of reflux disease and here we investigate whether alginates can influence pepsin activity, a major aggressor in reflux disease. The primary uronic acid structure of alginates can be altered using epimerase technology and we test tailor-made alginates to identify the optimal structure for pepsin inhibition. Pepsin activity in the presence of alginates was studied using an in vitro N-terminal assay and enzyme kinetics using a chromagenic peptide. The data described showed clearly that alginates were capable of concentration dependently reducing the activity of pepsin in a non-competitive manner, in vitro. This was variable between different alginates of wide ranging structure and size with positive correlation with alternating sequences of mannuronic and guluronic acid. We hypothesize that alginates may have a more extensive role in the treatment of reflux disease by inhibiting pepsin, a damaging component of the refluxate.

Gastroesophageal reflux and cancer

The causal relationship between GERD and esophageal adenocarcinoma, although unclear just a few decades ago, now is established fairly well. The physiologic changes and the biocellular alterations of the damaged esophageal mucosa are documented better. Despite this knowledge, the dramatic increase in the incidence of esophageal cancer cannot be explained. The absolute risk of esophageal adenocarcinoma arising from GERD is low, and, at present, does not justify population-screening programs. Still, with the notion that adenocarcinoma of the esophagus is an aggressive cancer once documented, important questions still are in need of answers for patients suffering from reflux symptoms. Patients who have reflux disease are not necessarily symptomatic. It remains unclear if patients experiencing reflux symptoms should undergo mandatory endoscopy with biopsies at the esophagogastric junction. Furthermore, metaplasia of the lower esophagus often is not readily recognizable at endoscopy, and only biopsies can document abnormal histology. A severe and prolonged history of reflux always should orient to the possibility of a reflux-related columnar-lined esophagus. Once documented, Barrett's esophagus needs to be seen as a premalignant condition not necessarily leading to adenocarcinoma formation; despite their increased risk of tumor formation, most patients who have Barrett's esophagus die of other causes. During regular endoscopic follow-up, multilevel circumferential biopsies should document the evolution of the histologic changes in the lower esophagus and at the gastroesophageal junction of these patients. It is the only method available to document the appearance of dysplasia. It still is unclear if medicine or surgery provides the best quality of life and the best protection against the development of dysplasia and the possible progression toward adenocarcinoma formation when intestinal metaplasia is present in the esophagus.

Acid challenge to the human esophageal mucosa: effects on epithelial architecture in health and disease

The histological changes that occur in the squamous epithelium in response to acute acid challenge was examined in healthy controls and proton pump inhibitor-treated gastroesophageal reflux disease (GERD) patients and related to the state of untreated erosive GERD in a saline-controlled, randomized perfusion study. In the basal state a stepwise significant increase in the thickness of the basal cell layer, papillary length, and dilatation of intercellular spaces (DIS) was seen when the three groups were compared. Acid perfusion induced a slight increase in the height of the basal cell layer mainly in healthy volunteers; this layer appears to be reactive to acute acid challenge as well as to acid suppressive therapy. DIS increases promptly in response to acute acid exposure in the healthy epithelium but no changes were seen in the lengths of the papillae or regarding DIS in the GERD patients. A protective effect of luminal nitric oxide on DIS development is suggested.

Pathogenesis of Gastroesophageal Reflux Disease

The pathophysiology of reflux esophagitis involves contact of the esophageal epithelium with acid-pepsin in the refluxate. For this contact to occur with sufficient duration, there must either be a combination of defects in antireflux and luminal clearance mechanisms for acid-pepsin to overwhelm a previously healthy epithelium or primary defects within the epithelium develop that subsequently enable 'normal' acid contact times to become damaging to the epithelium. This report examines these 2 pathways to reflux esophagitis and questions the causative role attributed to some phenomena. In either case, the final common pathway for the clinical expression of reflux esophagitis is by damage to the esophageal epithelium that is responsible for the development of heartburn and/or esophageal necrosis and inflammation.

Bile in the esophagus: a factor in the pathogenesis of reflux esophagitis in children

OBJECTIVES

Bile reflux has been postulated to be an important factor contributing to gastroesophageal reflux disease in adults. The purpose of this study was to investigate its role in children.

METHODS

Sixty-five children with symptoms of gastroesophageal reflux disease were classified on the basis of the endoscopic grade of reflux esophagitis: no esophagitis (n = 26), mild to moderate esophagitis (n = 26), and severe esophagitis (n = 13). Simultaneous 24-hour esophageal pH and bilirubin monitoring with Bilitec 2000 was performed.

RESULTS

Both bile and acid reflux increased with the severity of esophagitis. The differences between all groups were significant for the percentage of total (P < 0.0005), upright (P < 0.05), and supine time (P < 0.0005) bilirubin absorbance > or = 0.14, as well as for the percentage of total and supine time pH < 4, and DeMeester score (P < 0.0005). Combined pathologic acid and bile reflux was found in 11% of children with mild esophagitis and in 70% of children with severe esophagitis, while isolated bile reflux was found in 31% and 7.5%, respectively. Combined pH and bilirubin monitoring, compared with ph-monitoring alone, increased the sensitivity from 56% to 79%, and the accuracy from 69% to 83%.

CONCLUSIONS

Both bile and acid reflux increase stepwise with the severity of esophagitis. Combined acid and bile reflux is associated with severe esophagitis. Isolated acid or bile reflux is usually present in mild esophagitis. Simultaneous esophageal pH and bilirubin monitoring has a higher sensitivity, as well as predictive values and accuracy than ph monitoring alone.

Pathogenesis of gastroesophageal reflux disease

The pathophysiology of GERD involves contact of the esophageal epithelium with acid/pepsin in the refluxate. For this contact to occur with sufficient duration, there must be a combination of defects in antireflux and luminal clearance mechanisms for acid/pepsin to overwhelm an intact epithelium, or defects within the epithelium develop that subsequently enable normal acid contact times to become damaging to the epithelium. In either case, the final common pathway is damage to the esophageal epithelium--damage that is reflected in the development of heartburn, esophageal necrosis and inflammation, or both.

Mechanisms of gastroesophageal reflux and gastroesophageal reflux disease

Gastroesophageal reflux is a physiological phenomenon, occurring with different severity and duration in different individuals. Reflux occurs when this normal event results in the occurrence of symptoms/signs or complications. The pathophysiology of gastroesophageal reflux is complex and diverse, since it is influenced by factors that are genetic, environmental (e.g., diet smoking), anatomic, hormonal, and neurogenic. However, many mechanisms remain incompletely understood. Future research should focus on a better understanding of the physiology of the upper and lower esophageal sphincters, and of gastric motility. The afferent and efferent neural pathways and neuropharmacologic mediators of transient lower esophageal sphincter relaxations and gastric dysmotility require further study. The role of anatomic malformations such as hiatal hernia in children has been underestimated. While therapeutic possibilities are greater in number and largely improved, the outcomes of some treatments are far from satisfactory in many cases. In addition to development of new forms of treatment, research should address better use of currently available medical and surgical treatments.

Duodenogastroesophageal reflux and methods to monitor nonacidic reflux

The role of duodenogastroesophageal reflux (DGER), once erroneously termed "bile reflux," in causing esophageal mucosal damage has been an area of interest in both animal and human studies. However, because of the lack of appropriate techniques to accurately measure DGER, extrapolation of findings from animal studies to humans has been difficult to make. The recent advent of the Bilitec system (Metronics Instruments, Minneapolis, MN), an ambulatory bilirubin monitoring device, is increasing our knowledge of the specific role of DGER in esophageal diseases. Studies suggest that DGER without acid reflux may result in symptoms, but unless acid reflux is present simultaneously, it does not cause esophagitis. Therefore, therapies should aim at reducing both DGER and acid reflux. Studies show that this may be accomplished by antireflux surgery or the use of proton pump inhibitors, which by reducing gastric volume, decrease the damaging potential of both acid and DGER.

Reflux and pH: 'alkaline' components are not neutralized by gastric pH variations

The ability of the 'alkaline' components of reflux to cause harm in vivo is still open to debate, although these components have been shown in vitro to be capable of damaging the mucosa. The precipitation of bile acids and lysolecithin that occurs at low pH values is the main reason for questioning in vivo mucosal damage. This study was undertaken to determine the composition of gastric aspirates at different original pH values and the degree of solubility of the alkaline components when pH modifications are artificially induced. The samples for chemical analysis were collected from indwelling nasogastric tubes after surgical procedures that did not involve the upper gastrointestinal tract. Bile acid and lysolecithin concentrations were assessed by means of dedicated methods. Thirty-five samples were available for bile acid evaluation and 27 for lysolecithin evaluation. Bile acid and lysolecithin assessments were repeated after pH adjustment at 2, 3.5, 5.5 and 7. For easier assessment of the results, three ranges of the original pH were selected (pH < 2, 2 < or = pH < 5, pH > or = 5). For each pH range, results were pooled together and compared with those in the other pH ranges. Bile acid concentrations were 113+/-48, 339+/-90 and 900+/-303 (mean +/- s.e.m. micromol/L), respectively, in the three groups selected on account of the different original pH values. Differences were significant (p < 0.001). Both taurine- and glycine-conjugated bile acids were represented even at pH < 2. No major differences were observed in bile acid concentration with the artificially induced pH variations. Lysolecithin concentrations were 5.99+/-3.27, 30.80+/-8.43 and 108.37+/-22.17 (mean +/- SEM microg/ml), respectively, in the three groups selected on account of the different original pH ranges. Differences were significant (p < 0.001). No significant differences in lysolecithin concentration were detected with the artificially induced pH variations. In conclusion, both bile acids and lysolecithin are naturally represented in the gastric environment even at very low pH values, although their concentrations decrease on lowering of the naturally occurring pH. Given the concentration variability of bile acids and lysolecithin, further studies are needed to assess the minimal concentration capable of mucosal damage in vivo.

Increased acid and bile reflux in Barrett's esophagus compared to reflux esophagitis, and effect of proton pump inhibitor therapy

OBJECTIVES

Barrett's metaplasia is an acquired condition resulting from longstanding gastroesophageal reflux disease. Approximately 10% of esophagitis patients develop Barrett's esophagus. There is increasing evidence that duodenogastroesophageal reflux plays a role in the progression of disease. We further analyzed the correlation of acid and biliary reflux with reflux esophagitis and Barrett's esophagus and tested the effects of proton pump inhibitor therapy.

METHODS

Patients with either reflux esophagitis (group 1) or Barrett's esophagus (group 2) prospectively underwent simultaneous 24-h esophageal pH and bile reflux testing without any therapy affecting acid secretion or GI motility. A total of 16 patients in group 1 and 18 patients in group 2 were tested again under proton pump inhibitor therapy.

RESULTS

Acid and bile exposure were significantly increased in Barrett's patients (n = 23) compared to 20 esophagitis patients (median percentage of time that pH was <4 was 24.6% vs 12.4%, p = 0.01, median percentage of time that bilirubin absorbance was >0.2 was 34.7% vs 12.8%, p < 0.05). During therapy, both acid and bile reflux decreased significantly in both groups. Median percentage of time that pH was <4 and bilirubin absorbance was >0.2 before and during therapy was 18.2%/2.3% and 29.8%/0.7% (p = 0.001 and p = 0.001) in Barrett's esophagus patients versus 14.5%/3.6% and 21.5%/0.9% (p = 0.002 and p = 0.011) in esophagitis patients. There was no significant difference between the groups. In two esophagitis patients, bile reflux increased during therapy.

CONCLUSIONS

There is a good correlation of the duration of esophageal exposure to acid and bile with the severity of pathological change in the esophagus. Both acid and bile reflux is significantly suppressed by proton pump inhibitor therapy with exceptions among individual esophagitis patients. The prolonged simultaneous attack of bile and acid may play a key role in the development of Barrett's metaplasia.

Review article: the role of non-acid reflux in gastro-oesophageal reflux disease

The role of acid in the pathogenesis of gastro-oesophageal reflux disease (GERD) has been extensively studied and is well accepted. The role, if any, of non-acid reflux, in particular duodenogastro-oesophageal reflux, is much debated. The availability of new technology to detect non-acid reflux has heightened interest in this question. This article reviews the following: How do we define non-acid reflux? Does duodenogastro-oesophageal reflux (alone or in combination) cause oesophageal injury, symptoms or both? What is its role in complicated GERD? What methods are available to assess non-acid reflux? Does non-acid reflux need treatment and if so what modalities are available?

Duodenogastro-oesophageal reflux

The role of duodenogastro-oesophageal reflux (DGOR), once erroneously termed 'bile reflux', in causing oesophageal mucosal damage has been an area of interest in both animal and human studies. However, due to the lack of appropriate techniques for accurately measuring DGOR, extrapolation of findings from animal studies to humans was difficult to make. The recent advent of the Bilitec system, an ambulatory bilirubin monitoring device, is increasing our knowledge of the specific role of DGOR in oesophageal diseases. Studies suggest that the DGOR without acid reflux may result in symptoms but unless acid reflux is present simultaneously, it does not cause oesophagitis. Therefore, our therapies should aim at reducing both DGOR and acid reflux. Studies show that this may be accomplished by anti-reflux surgery or the use of proton pump inhibitors, which, by reducing gastric volume, decrease the damaging potential of both acid and DGOR.

Studies on experimental animals involving surgical procedures and/or nitrosamine treatment related to the etiology of esophageal adenocarcinoma

After a brief review of the epidemiology and etiology of lower esophageal adenocarcinoma (EAC), this paper describes long-term experiments on animals (mostly rats) demonstrating that reflux of duodenal contents into the stomach can induce gastric and pancreatic cancer, that gastric reflux into the esophagus can induce Barrett's esophagus; that esophagoduodenostomy to facilitate duodenal reflux into the esophagus, together with administration of carcinogenic nitrosamines, induces squamous cancer and EAC in the lower esophagus; that both pancreatic juice and bile are involved in this induction of EAC; that a high-fat diet increases EAC induction; and that esophagoduodenostomy with gastrectomy and nitrosamine treatment or esophagojejunostomy without a carcinogen can produce up to an 88% incidence of EAC. Short-term animal experiments are reviewed in which bile salts and trypsin have damaged the esophagus and duodenal reflux has produced lipid peroxidation in the lower esophagus. Finally, I review arguments mostly derived from the animal experiments that reflux of unacidified duodenal juice via the stomach into the lower esophagus may help cause Barrett's esophagus and EAC, that excessive use of acid blockers might contribute to EAC induction, and that EAC induction may be reduced by surgery to repair the lower esophageal sphincter or perhaps by taking non-steroidal anti-inflammatory drugs.

Bile in the oesophagus: clinical relevance and ambulatory detection

BACKGROUND

Experimental work in animals has implicated a role for bile in the pathogenesis of several oesophageal mucosal diseases such as oesophagitis, Barrett's oesophagus and oesophageal adenocarcinoma. Recent descriptions of a high incidence of intestinal metaplasia at the gastro-oesophageal junction in patients without a classical 3-cm Barrett's columnar-lined segment, combined with a rising incidence in oesophageal and cardia adenocarcinoma, have stimulated interest in the causes of these conditions.

METHODS AND RESULTS

Animal studies concerned with defining the role of the various gastroduodenal reflux constituents in oesophageal mucosal injury are summarized and evidence for bile in the pathogenesis of Barrett's oesophagus and oesophageal adenocarcinoma is reviewed. The results of various techniques for clinical measurement of oesophageal bile reflux, such as aspiration, scintigraphy and pH monitoring, are evaluated and the significance of recent studies employing ambulatory fibreoptic bilirubin monitoring is discussed.

CONCLUSION

There seems little doubt that bile plays a significant role in oesophageal mucosal disease, in synergy with other constituents of reflux. Although ambulatory bilirubin monitoring is new, some intriguing findings have been reported and it is hoped that this technique will continue to shed light on the role of bile in the oesophagus.

The application of microridge analysis in the diagnosis of gastro-oesophageal reflux disease

BACKGROUND

The percentage of epithelial surface area covered by microridges (%MR) seen during scanning electron microscopy of oesophageal biopsy specimens has previously been shown to correlate with symptomatic reflux disease, a result < or = 35% being abnormal. The aim of this study was to compare %MR with endoscopy, light microscopy, and pH monitoring results.

METHODS

Sixty-seven patients with heartburn were divided into oesophagitis or none on the basis of endoscopy and light microscopy findings and into those with and without abnormal acid reflux on the basis of pH monitoring.

RESULTS

The endoscopic and light microscopic oesophagitis groups had significantly greater degrees of acid reflux than those without oesophagitis (p < 0.05), even though neither the specific %MR nor the number of patients below the 35% cutoff showed any difference between those with and without endoscopic oesophagitis, light microscopic oesophagitis or those with normal and abnormal acid reflux on pH monitoring.

CONCLUSION

Despite the significant relationship between endoscopic and light microscopic oesophagitis and abnormal pH monitoring microridge analysis did not correlate with any of these variables

Role of acid and duodenogastric reflux in esophageal mucosal injury: a review of animal and human studies

The role of acid and duodenogastric reflux (DGR) in the development of esophageal mucosal injury has been extensively investigated using both animal and human models. In this report, clinical and experimental data are reviewed. The mechanisms by which gastric and duodenal contents produce esophageal mucosal injury are also discussed. Acid and pepsin are unquestionably important in causing mucosal damage at low pH values in both animal and human models. Animal models suggest synergistic damaging potential for conjugated bile acids and HCI as well as that of unconjugated bile acids and trypsin in more neutral pH values. Human evidence for the involvement of bile and its constituents has been controversial; however, the advent of better technology to detect DGR is beginning to clarify the role of these constituents. The contribution of each methodology in clarifying the extent of involvement of DGR in esophageal mucosal injury is reviewed. Despite some conflicting results, preliminary human studies support the results from the animal data suggesting synergistic damaging effects for both bile and acid in esophageal mucosal injury. The implication of these studies in treating gastroesophageal reflux disease are discussed.

Duodenogastroesophageal reflux: relationship to pH and importance in Barrett's esophagus

BACKGROUND/AIMS

Several reports suggest that duodenogastroesophageal reflux may produce esophagitis, Barrett's esophagus, and esophageal adenocarcinoma. The purpose of this study was to understand better the relationship of pH (< 4 and > 7), duodenogastroesophageal reflux, and fasting bile acid concentrations in producing esophageal damage.

METHODS

Using a spectrophotometric technique to measure bile reflux, four groups were studied: healthy subjects, reflux patients, patients with Barrett's esophagus, and patients with esophageal symptoms after partial gastrectomy.

RESULTS

Simultaneous 24-hour pH and bile monitoring of distal esophagus found close association between total percent of time pH < 4 and duodenogastroesophageal reflux (r = 0.78; P < 0.001) but a poor relationship (r = -0.06) with total percent of time pH > 7, suggesting that the term alkaline reflux is a misnomer. Duodenogastroesophageal reflux increased significantly with the severity of reflux disease, being greatest in patients with Barrett's esophagus and comparable with that in patients with partial gastrectomy. Fasting bile acid concentrations did not distinguish patients with Barrett's esophagus from those with reflux. Rather, increased quantity of acid reflux was the single factor most characterizing patients with Barrett's esophagus. Omeprazole (20 mg twice daily) normalized acid reflux parameters (13.8% +/- 1.6% to 0.8% +/- 0.6%) and significantly (P < 0.001) decreased duodenogastroesophageal reflux (32.8% +/- 6.9% to 4.7% +/- 1.7%).

CONCLUSIONS

Acid reflux is the primary factor in the development of Barrett's esophagus. Bile reflux parallels acid reflux and, at best, may have a synergistic role. Aggressive acid suppression with omeprazole markedly decreases both.

Determinants of oesophageal 'alkaline' pH environment in controls and patients with gastro-oesophageal reflux disease

The determinants of the oesophageal alkaline pH environment are poorly understood. Saliva (pH 6.4-7.8) may be a major contributor, although some argue the importance of refluxed alkaline duodenal contents. Acid and alkaline reflux parameters were studied over 2 days in 30 subjects (control, oesophagitis and Barrett's patients; 10 each) using glass pH electrodes. In phase 1, one pH electrode was placed 1 cm below the upper oesophageal sphincter to assess the influence of saliva and the other 5 cm above the lower oesophageal sphincter. Phase 2 was identical except that one pH probe was 5 cm below the lower oesophageal sphincter to record duodenogastric reflux. Patient groups spent, on average, 50 fold more time during the upright and supine periods at acidic pH than controls. Saliva was responsible for the percentage of time the pH > 7 and contributed significantly to the percentage of time the pH > 6 in both the proximal and distal oesophagus of control subjects, as shown by an absence of pH > 7 and a significant (p < 0.001) fourfold decrease in pH > 6 during sleep. A similar pattern was seen in the proximal oesophagus of both reflux groups. The reflux and Barrett's patients, however did not show a significant decrease in the percentage of time the pH > 6 at night in the distal oesophagus suggesting a relative increase in 'alkaline' exposure from another source. This was not because of duodenogastric reflux as the corresponding pH rises in the fundus of the stomach were non-existent. Although this was not studied specifically, it is believed to be a protective meachanism, the result of alkaline secretion produced by submucosal oesophageal glands.

Bile acids do not modify the effects of pepsin on the fine structure of human oesophageal epithelium

Oesophageal mucosal specimens (n = 250) were taken from 25 normal subjects (14 females, 11 males; median age 52 years; range 19-63 years) and incubated in physiological saline, pepsin and bile acid solutions to determine whether conjugated bile acids modify the epithelial cytotoxic action of pepsin. Short (5 min) and long (22 min) incubations were carried out and the results were assessed by transmission electron microscopy. Six different parameters of epithelial damage were scored (0-4) by a single 'blinded' pathologist for each of four epithelial layers. The scores after incubation in saline (pH 7 and titrated to pH 2 with HCl) were not different from those of the controls (P = 0.35). Both pepsin and bile acids (pH 2) caused more damage than saline at pH 2 (P less than 0.001) which was similar for the two substances (P = 0.136). Conjugated bile acids in combination with pepsin (pH 2) did not alter the overall extent or pattern of damage caused by pepsin alone (pH 2); P = 0.142). Conjugated bile acids, in concentrations commonly encountered during gastro-oesophageal reflux, did not appear to modify the cytopathic effects of pepsin on oesophageal mucosal cells in vitro. Conjugated bile acids may not be important in the pathogenesis of oesophagitis in patients with acid/peptic gastro-oesophageal reflux.

In vivo alkaline secretion by mammalian esophagus

Alkaline secretion (AS) was sought in vivo in the rabbit and opossum esophagus, using a recirculated unbuffered saline solution and pH stat technique. The rabbit and opossum were used because both have stratified squamous epithelium; however, only the opossum has, in addition, an extensive network of submucosal glands. Mean basal AS in the rabbit was 0.02 +/- 0.005 muEq/h . cm2, with one-third of the animals having no AS. Basal AS was present in all opossums with a mean value 20-fold greater than in rabbits (0.39 +/- 0.03 muEq/h . cm2). Basal AS in both species was found by titration methodology to be comprised almost entirely of secreted bicarbonate ions. In the rabbit, AS could not be stimulated by luminal HCl, i.v. carbachol, or i.v. NaHCO3. In contrast, luminal HCl stimulated AS in opossums three- to fourfold above basal values, and neither the acid-stimulated nor basal AS in the opossum was blocked by i.v. atropine. Acid clearance by AS was monitored in both species in vivo. In the rabbit, pH increased from 2.0 to 3.6 in 1 h, with a steady rate of rise after equilibration of 0.1 pH units/10 min. In the opossum, pH increased from 2.0 to 6.4 in 1 h, with a steady rate of rise five times faster than rabbits (0.5 pH units/10 min). These results indicate that the mammalian esophagus can secrete a bicarbonate-containing fluid with the capacity to clear acid from the esophageal lumen. The major source of this secretion is not the squamous epithelium, but probably the submucosal glands. Because the human esophagus has both submucosal glands and a mechanism for acid clearance consistent with the presence of AS, the findings in opossums may have relevance to protection against reflux disease in humans.

Serosal bicarbonate protects against acid injury to rabbit esophagus

The role of serosal bicarbonate ions (HCO3-) in protection against acid injury was investigated in rabbit esophageal mucosa mounted in Ussing chambers. Luminal acidification reduced potential difference and resistance in tissues exposed serosally to HCO3- or (unbuffered) HCO3-free solution. Whereas resistance declined similarly in both groups, potential difference declined less in HCO3- solution. After washout, HCO3-bathed tissues also had a greater increase in resistance, lower permeability to mannitol, and less histologic damage. Furthermore, as protection by HCO3- was not blocked by pretreatment with either the anion exchange blocker, 4 acetamido-4'-isothiocyanatostilbene 2-2'-disulfonic acid, or the carbonic anhydrase inhibitor, acetazolamide, and replacement of HCO3- with N-2-hydroxyethylpiperazine-N'-2-ethane sulfonic acid, a buffer impermeant to cells, was protective, an extracellular site for protection by HCO3- was likely. Where in the extracellular space HCO3- buffers H+ is unclear, but the absence of change in luminal pH and the inability to prevent the acid-induced increase in permeability in HCO3-bathed tissues argue against a luminal (preepithelial) site. Also, rapid repair was not demonstrated, indicating that a luminal site for protection after surface cell damage was unlikely. We conclude that serosal HCO3- is important in esophageal protection against acid damage by buffering H+ within the intercellular compartment of the extracellular space.

Bile acid concentrations in the refluxate of patients with reflux oesophagitis

Although reflux of bile acids has been implicated in the pathogenesis of reflux oesophagitis, attempts to document this in vivo have failed to detect more than trace amounts of bile acid in the oesophagus. To determine the bile acid composition of oesophageal refluxate, 45 patients with abnormal acid gastro-oesophageal reflux with oesophagitis and 10 controls had a size 14 Fr Salem sump tube positioned 5 cm above the lower oesophageal sphincter. Oesophageal contents were continuously aspirated and collected in aliquots every 2 h over 16 h. Fasting, postprandial, upright and supine (nocturnal) periods were assessed and total conjugated bile acids were measured by high pressure liquid chromatography with a sensitivity of 8 mumol/l. Conjugated bile acids were detected in 2 of 10 controls (maximum 40 mumol/l) and in 39 of 45 patients (87 per cent). Eleven patients had peak conjugated bile acid levels greater than 200 mumol/l, and these levels occurred exclusively during the supine (nocturnal) period. Median conjugated bile acid levels during daytime reflux were less than 20 mumol/l which was significantly lower than during nocturnal reflux (median 51 mumol/l, P less than 0.001). Conjugated bile acids are detected in the oesophagus of most patients with oesophagitis and may play a role in the pathogenesis of oesophagitis in some patients with nocturnal gastro-oesophageal reflux.

24-hour esophageal pH monitoring before and after medical therapy for reflux esophagitis

Medical treatment of gastroesophageal reflux disease often results in improvement of symptoms. The purpose of this study was to determine if improvement in symptoms and endoscopic appearance after treatment was associated with a reduction in reflux, as measured with 24-hr pH recordings. Twenty patients with severe chronic reflux esophagitis participated in an eight-week double-blind trial of medical therapy with metoclopramide and cimetidine versus placebo and cimetidine. Significant symptom score improvement was noted in 11 patients. Eleven patients also had improvement in the endoscopic appearance of the esophageal mucosa, and eight of these patients had significant symptom improvement. Initial 24-hr pH recordings were abnormal in all patients, evidenced by an esophageal pH less than 4 during 20% of the study period. Improvement in 24-hr results was noted in only five patients--three with clinical and endoscopic improvement, and two with no improvement. In conclusion, there was no relationship between clinical improvement and the results of 24-hr pH recordings. Successful symptom relief and endoscopic healing of esophagitis during medical treatment may occur despite persistent reflux of gastric contents.

Morphological changes caused by exposure of rabbit oesophageal mucosa to hydrochloric acid and sodium taurocholate

The present authors have studied the light and electron microscopic changes in rabbit oesophageal mucosa which has been exposed to solutions of hydrochloric acid and sodium taurocholate (ST). In an in vivo model the oesophagus was perfused with saline, acid (0.1-40 mmol/l of H+) or taurocholate (0.1-1.0 mmol/l at pH 2.0 or 1.0 mmol/l at neutral pH). At the end of each perfusion experiment the oesophagus was removed and assessed by the naked eye, light and electron microscopy. Some desquamation of superficial stratum corneum cells occurred in all specimens perfused for 5 h. Injury was more evident to the stratum spinosum and basal cell layers. Damage was more severe in the bile salt plus acid perfused specimens, varying between margination of nuclear chromatin in the basal cells to complete necrosis and separation of the overlying layers. Taurocholate in neutral solution did not damage the oesophageal epithelium. Electron microscopy revealed that damage to cells in the basal layers and stratum granulosum occurred within 30 min of exposure to acidified taurocholate, this damage increasing with time. It is concluded that taurocholate is able to damage oesophageal mucosa, that the damage first occurs in the deeper layers of the oesophageal mucosa and that the damage may occur in the absence of gross or light microscopic changes in the mucosa.