Recent views on the pathogenesis of gastro-oesophageal reflux disease

Insights into the genetics of gastroesophageal reflux disease (GERD) and GERD-related disorders

Gastroesophageal reflux disease (GERD) is associated with obesity and hiatal hernia, and often precedes the development of Barrett's esophagus (BE) and esophageal adenocarcinoma (EA). Epidemiological studies show that the global prevalence of GERD is increasing. GERD is a multifactorial disease with a complex genetic architecture. Genome-wide association studies (GWAS) have provided initial insights into the genetic background of GERD. The present review summarizes current knowledge of the genetics of GERD and a possible genetic overlap between GERD and BE and EA. The review discusses genes and cellular pathways that have been implicated through GWAS, and provides an outlook on how future molecular research will enhance understanding of GERD pathophysiology.

Prevalence of gastroesophageal reflux in a Tunisian primary care population determined by patient interview

Although gastresophageal reflux disease (GERD) is highly prevalent in Western countries, we have very little data about it in African countries. The aim of the study is to determine the prevalence and severity of GERD symptoms among Tunisian subjects and report its characteristics, consultation rate, management modes, as well as patients' satisfaction. Five hundred subjects living in Tunisia were interviewed face to face. The study was conducted at seven centers of primary care at Monastir's department by six interviewer doctors. The questionnaire consisted of 30 questions relating to subject attributes, lifestyle factors, medical history, reflux-related symptom characteristics, consultation behavior, previous treatments for GERD, and description of the last episode. Symptoms were defined as 'frequent' if they occurred at least weekly and 'occasional' if they occurred less frequently during the last year. The mean age was 42.3 ± 17.3 years and 75.6% were females. Over the previous year, 60% of the respondents reported suffering any GERD symptom. The prevalence of frequent GERD is 24%. Female gender (odds ratio [OR]: 1.97[1.15-3.37]) and body mass index ≥ 25 (OR: 1.54[1.042-2.29]) were associated with increased risk of GERD symptom. Only 22.3%, sought medical advice about GERD symptoms in the last year. In the univariate and multivariate analysis, work status, frequency and intensity of symptoms, duration of symptom, and association of atypical symptoms were associated with a higher frequency of medical consultation for GERD symptoms. Among the subjects complaining about heartburn, 34% took medications. GERD symptoms are common among Tunisian subjects. Few heartburn sufferers seek medical attention, and most do not take medications for symptomatic control.

The relationship between the control of pH and healing and symptom relief in gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GERD) is generally considered to be the result of a motility disorder which permits the abnormal and prolonged exposure of the lumen of the oesophagus to the acidic gastric contents. This view is supported by experimental data, intra-oesophageal pH measurement, and the dramatic results of symptom relief and healing seen with effective antisecretory treatment. Oesophageal mucosal injury is determined by the pH of the refluxate and duration of acid exposure. Most patients experience meal-stimulated reflux during the day and the more severe cases experience 24-h acid exposure. In contrast to the H2-receptor antagonists (H2RAs), the proton pump inhibitors (PPIs) are more effective at controlling meal-stimulated acid secretion when each is given in standard doses. Therefore, the degree and duration of acid suppression throughout 24 h is greater. Treatments which maintain intra-oesophageal pH > 4 for 96% or more of the 24 h normalize acid exposure and are associated with the highest healing rates. Peptic activity is minimized at or above pH 4. The time above pH 4 is significantly longer with the PPIs than with the H2RAs. Thus, the healing-time curves for GERD (grades II-IV) are shifted to the left for the PPIs which heal a significantly greater proportion of patients earlier than the H2RAs or sucralfate. Symptoms in GERD are related to the degree and duration of oesophageal acid exposure. Symptom relief is more rapid and complete with the PPIs than with the H2RAs or other treatments in standard doses.

Risk factors for gastro-oesophageal reflux disease symptoms: a community study

AIM

To examine the prevalence of gastro-oesophageal reflux disease symptoms and potential risk factors among community subjects.

METHODS

A questionnaire was sent to 4000 subjects, stratified by age, gender and ethnicity to be representative of the local population. Gastro-oesophageal reflux disease symptoms were defined as at least weekly heartburn or acid regurgitation.

RESULTS

2231 responded (59%), 691 refused to participate and seven were incomplete. 1533 (41%) were evaluable (637 male, mean age 51 years, range: 20-80). The prevalence of gastro-oesophageal reflux disease symptoms was 21%. Smoking, excess alcohol, irritable bowel syndrome, increasing body mass index, a family history of upper gastrointestinal disease, increasing Townsend deprivation index, anticholinergic drugs (all P < 0.0001), weight gain, antidepressant drugs, inhaled bronchodilators, no educational attainment (all P < 0.01), south Asian origin (P = 0.02) and manual work (P < 0.05) were associated with gastro-oesophageal reflux disease symptoms. Multivariate logistic regression revealed increasing body mass index, a family history of upper gastrointestinal disease, irritable bowel syndrome, south Asian origin (all P < 0.0001), smoking, excess alcohol, no educational attainment and anticholinergic drugs (all P < 0.01) were independently associated with gastro-oesophageal reflux disease symptoms.

CONCLUSIONS

Frequent gastro-oesophageal reflux disease symptoms affect 21% of the population. Increasing body mass index, a family history of upper gastrointestinal disease, irritable bowel syndrome, south Asian origin, smoking, excess alcohol, social deprivation and anticholinergic drugs are independently associated with gastro-oesophageal reflux disease symptoms.

Management of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is a chronic condition requiring long-term treatment. Simple lifestyle modifications are the first methods employed by patients and, because of their low cost and simplicity, should be continued even when more potent therapies are initiated. Potent acid-suppressive therapy is currently the most important and successful medical therapy. Whereas healing of the esophageal mucosa is achieved with a single dose of any proton pump inhibitor (PPI) in more than 80% of cases, symptoms are more difficult to control. Patients with persistent symptoms on therapy should be tested (preferably with combined multichannel intraluminal impedance and pH) for association of symptoms with acid, nonacid, or no GER. Long-term follow-up studies indicate that PPIs are efficacious, tolerable, and safe medication. So far, promotility agents have shown limited efficacy, and their side-effect profile outweighs their benefits. Antireflux surgery in carefully selected patients (ie, young, typical GERD symptoms, abnormal pH study, and good response to PPI) is as effective as PPI therapy and should be offered to these patients as an alternative to medication. Still, patients should be informed about the risks of antireflux surgery (ie, risk of postoperative dysphagia; decreased ability to belch, possibly leading to bloating; increased flatulence). Endoscopic antireflux procedures are recommended only in selected patients and given the relative short experience with these techniques, patients treated with endoscopic procedures should be enrolled in a rigorous follow-up program.

Is motility impaired in the entire upper gastrointestinal tract in patients with gastro-oesophageal reflux disease?

BACKGROUND

Although the pathogenesis of gastro-oesophageal reflux disease is multifactorial, abnormal function of the lower oesophageal sphincter has been established, and in some cases motility defects in the oesophageal body has been described. In some patients with gastro-oesophageal reflux disease delayed gastric emptying has also been observed.

METHODS

Oesophageal and gastric motor function, as evaluated by use of scintigraphy and manometry, were studied concomitantly in 105 patients with chronic, gastro-oesophageal reflux disease before and after antireflux surgery. In a subgroup of these patients (n = 29) similar data were retrieved also at 2.7 years after antireflux surgery.

RESULTS

Impaired oesophageal motor function expressed as delayed transit of a labelled bolus was closely associated with motor dysfunction also recorded in the stomach as determined by delayed emptying of labelled solid food items. A similar relationship was found when oesophageal motor dysfunction was characterized as the frequency of failed primary peristalses after water swallows during manometry. When the 105 patients were studied half a year after an antireflux operation, noncorrelation between oesophageal and gastric motor function could be recorded.

CONCLUSIONS

These data further substantiate the view that gastro-oesophageal reflux disease is associated with a disturbed motor function within the entire upper gastrointestinal tract.

The pathophysiology of gastro-oesophageal reflux disease: an overview

Gastro-oesophageal reflux disease (GORD) is a multifactorial disease. Although it is primarily a motility disorder, several other disturbances can interfere and contribute to determine the severity of symptoms and the degree of lesions. In normal subjects, as in patients with pathological reflux, nearly all the episodes of reflux obey one of the following three mechanisms: (a) a transient complete relaxation of the lower oesophageal sphincter (TLOSR), (b) a transient increase in intra-abdominal pressure which overcomes the resistance of the antireflux barrier ('stress reflux') and, (c) a spontaneous reflux through a permanently hypotonic sphincter. Gastric distension is the major factor that can induce TLOSRs. Whereas, at rest, the diaphragm probably plays little role in cardial competence, diaphragmatic contraction may help prevent reflux in conditions resulting in increased abdominal pressure such as during physical activity and abdominal staining. The presence of a hiatal hernia increases susceptibility to reflux. A delayed gastric emptying may also facilitate reflux and represents a factor of resistance to antireflux therapy. Most studies in humans have shown that motor abnormalities remain unchanged after healing of oesophagitis. Acid and pepsin are the most noxious agents of the upper gastrointestinal secretions that can participate in the pathogenesis of oesophagitis. However, there is no evidence that patients with reflux have greater acid secretion than subjects without reflux. The clearance function is a two-stage phenomenon requiring first a reduction in volume by peristalsis and then chemical neutralization by saliva. Primary peristalsis is mainly responsible for the clearance of acid in both the upright and the supine positions. It takes longer to clear acid in patients with non-reducing hiatal hernia. The layer of mucus which carpets the mucosa comes from the saliva and also from the submucosal glands of the oesophagus. The paracellular pathway is the major route by which mucosal HCl enters and then damages the oesophageal epithelium. Only a minority of acid reflux episodes are accompanied by symptoms. The acid exposure during the time period that precedes a reflux episode (i.e. the acid burden) is a key factor determining whether that reflux episode will be symptomatic or asymptomatic.

Omeprazole and high dose ranitidine in the treatment of refractory reflux oesophagitis

Thirty two consecutive patients (age range 6 months-13.4 years) with severe reflux oesophagitis were randomised to a therapeutic trial for eight weeks during which they received either standard doses of omeprazole (40 mg/day/1.73 m2 surface area) or high doses of ranitidine (20 mg/kg/day). Twenty five patients completed the trial (12 on omeprazole, 13 on ranitidine). At entry and at the end of the trial patients underwent symptomatic score assessment, endoscopic and histological evaluation of the oesophagus, and simultaneous oesophageal and gastric pH measurement; results are given as median (range). Both therapeutic regimens were effective in decreasing clinical score (omeprazole before 24.0 (15-33), after 9.0 (0-18); ranitidine before 19.5 (12-33), after 9.0 (6-12)), in improving the histological degree of oesophagitis (omeprazole before 8.0 (6-10), after 2.0 (0-60); ranitidine before 8.0 (8-10), after 2.0 (2-6), and in reducing oesophageal acid exposure, measured as minutes of reflux at 24 hour pH monitoring (omeprazole before 129.4 (84-217), after 44.6 (0.16-128); ranitidine before 207.3 (66-306), after 58.4 (32-128)) as well as intragastric acidity, measured as median intragastric pH (omeprazole before 2.1 (1.0-3.0), after 5.1 (2.2-7.4); ranitidine before 1.9 (1.6-4), after 3.4 (2.3-5.3)). Serum gastrin concentration was > 150 ng/l in four patients on omeprazole and in three patients on ranitidine. It is concluded that in children with refractory reflux oesophagitis high doses of ranitidine are comparable with omeprazole for the healing of oesophagitis and relief of symptoms; both drugs resulted in efficacious reduction of intragastric acidity and intra-oesophageal acid exposure.

Relations among autonomic nerve dysfunction, oesophageal motility, and gastric emptying in gastro-oesophageal reflux disease

Recent studies suggest that vagal nerve dysfunction may be important in the aetiology of gastro-oesophageal reflux disease. Delayed oesophageal transit and slowed gastric emptying occur frequently and may also be of pathogenic importance. In 48 patients with gastro-oesophageal reflux disease we studied the prevalence of and relations between autonomic nerve dysfunction (as assessed by cardiovascular reflex tests) and oesophageal transit, oesophageal motility, gastric emptying, and endoscopic grade of oesophagitis. Of the 48 patients, 21 (44%) had abnormal autonomic nerve function, which was predominantly parasympathetic. Oesophageal transit was delayed in 28% of the patients and gastric emptying of the solid component of the meal was delayed in 46%. Oesophageal transit was significantly (p less than 0.007) slower in patients with abnormal autonomic nerve function. The percentage of synchronous oesophageal contractions was related to the score for autonomic nerve dysfunction (r = 0.40, p less than 0.05). There was no significant relation of autonomic nerve dysfunction to either delayed gastric emptying or endoscopic grade of oesophagitis. We conclude that in gastro-oesophageal reflux disease there is a high prevalence of parasympathetic nerve dysfunction which relates to delayed oesophageal transit and abnormal peristalsis and may therefore be of pathogenic importance.

Chronic persistent cough and gastro-oesophageal reflux

Chronic cough persisting for two months or more that remains unexplained after extensive investigations is a common clinical problem. The purpose of this study was to determine whether such cough is associated with otherwise asymptomatic gastro-oesophageal reflux. Thirteen patients with chronic persistent cough that was unexplained after a standard diagnostic assessment were identified. All were non-smokers. The mean (SE) duration of cough was 17.8 (8.0) months. Ten had never had reflux symptoms and three had had mild symptoms only after the onset of the cough. All the patients completed standardised cough diary cards for eight weeks and underwent 24 hour ambulatory oesophageal pH monitoring. A reflux episode was defined as a fall in oesophageal pH to below 4.0. Nine control subjects were matched for age, lung function, and body mass index. The patients experienced significantly more episodes of reflux per 24 hours than the controls (115.8 (SE 31.7) versus 4.7 (1.4) and longer reflux episodes (15.5 (5.8) versus 1.7 (0.5) minutes), and the oesophageal pH was below 4.0 considerably longer (84.5 (20.2) versus 3.8 (1.3) minutes). Cough occurred simultaneously with 13% (2.2%) of reflux episodes and within five minutes in another 35% (5.8%) of episodes, whereas gastro-oesophageal reflux occurred simultaneously with 78% (5.5%) of cough episodes and within five minutes in another 12% (2.3%) of episodes. It is concluded that chronic persistent cough that remains unexplained after a standard diagnostic assessment is associated with otherwise asymptomatic gastro-oesophageal reflux. It is suggested that a self perpetuating mechanism may exist whereby acid reflux causes cough via a local neuronal oesophageal-tracheo-bronchial reflex, and the cough in turn amplifies reflux via increased transdiaphragmatic pressure or by inducing transient lower oesophageal sphincter relaxation. Further study of this mechanism and the role of specific antireflux treatment in chronic persistent cough is warranted.

Dimethylphenylpiperazinium (DMPP)-induced relaxation and elevation of cyclic GMP content in canine lower esophageal sphincter (LES)

Cyclic GMP has been proposed as an intracellular mediator of neuronally-induced relaxation in lower esophageal sphincter (LES) smooth muscle. If cyclic GMP is indeed an intracellular messenger, then agents that activate enteric neurons of the sphincter [e.g. the ganglionic nicotinic receptor agonist dimethylphenylpiperazinium (DMPP)] also should cause a relaxation that is associated with an increase in cyclic GMP content. In isolated smooth muscle strips of canine LES, DMPP produced a rapid relaxation that was accompanied by a significant (P less than 0.05) increase in cyclic GMP content with no change in cyclic AMP content. Pretreatment of tissues with either tetrodotoxin or hexamethonium antagonized both the DMPP-induced relaxation and the associated increase in cyclic GMP. The combination of phentolamine and meclofenamic acid also antagonized both the relaxation and the elevation of cyclic GMP produced by DMPP. Electrical field stimulation (EFS)-induced relaxation and elevation in cyclic GMP was unaltered by meclofenamic acid and phentolamine. In conclusion, DMPP (like neuronal electrical activation) relaxed isolated canine LES through an enteric neuronal inhibitory pathway. The presence of phentolamine and meclofenamic acid did not affect EFS-induced effects, but blocked both the relaxation and the increase in cyclic GMP produced by DMPP, suggesting a more complicated pathway for DMPP in the release of inhibitory transmitter.

Pattern of acid reflux in patients with reflux esophagitis 'resistant' to H2-receptor antagonists

Ambulatory 24-h esophageal pH monitoring was carried out in 54 patients with erosive/ulcerative reflux esophagitis before a 12- to 24-week treatment with either ranitidine, 150 to 300 mg twice daily, or famotidine, 20 to 40 mg twice daily. After this period, 21 patients continued to present endoscopic evidence of esophagitis. Patients who did not respond to the therapy showed a more severe pretreatment pattern of acid reflux than those who healed, with regard to both median percentage time of reflux (16.2% versus 11.0%, respectively, p less than 0.05) and median number of reflux episodes (88.0 versus 55.0; p less than 0.05). Ambulatory 24-h esophageal pH-metry is therefore to be recommended in all patients with acid reflux symptoms, even in those who already show endoscopic lesions of the esophageal mucosa, since this test is a valid prognostic indicator of response to treatment.

A double-blind dose ranging study of BRL 24924 and metoclopramide on lower oesophageal sphincter pressure in healthy volunteers

1. A double-blind placebo controlled dose ranging study of the effect of single oral doses of 1 and 2 mg BRL 24924 and 10 mg metoclopramide on lower oesophageal sphincter pressure has been performed in 20 healthy volunteers. 2. The 2 mg dose of BRL 24924 caused a statistically significant increase in mean lower oesophageal sphincter pressure (P less than 0.05) at 30-45 min post-dose (20.8 +/- 7.1 cm H2O BRL 24924; 16.4 +/- 5.7 cm H2O placebo). BRL 24924 1 mg and metoclopramide 10 mg failed to increase lower oesophageal sphincter pressure at any time. However, eight volunteers with a hypotensive resting lower oesophageal sphincter pressure (less than 15 cm H2O) showed a statistically significant rise in pressure at 120 min for both 1 mg, 2 mg (P less than 0.01; P less than 0.001) BRL 24924 and 10 mg metoclopramide (P less than 0.01). No other significant effect was detected on oesophageal manometry. 3. BRL 24924 (2 mg) has statistically significant effects on lower oesophageal sphincter pressure. However, further studies in patients with gastro-oesophageal reflux disease and oesophagitis are needed to evaluate its clinical efficacy, especially where a hypotensive lower oesophageal sphincter pressure predominates.