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Keywords:

  • oesophagus;
  • gastro-oesophageal reflux disease;
  • motility;
  • pH-monitoring

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Abstract  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.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Proximal oesophageal extent of acid reflux is a determinant of symptom elicitation in gastro-oesophageal reflux disease (GORD) patients.1–3 Previous multi-sensor pH-studies have shown a higher percentage of proximal reflux in oesophagitis patients when compared with non-erosive reflux disease (NERD) patients and healthy controls.2 Moreover, proximal oesophageal and hypopharyngeal reflux are increased among patients with extra-oesophageal symptoms and complications of GORD.4–8 Indeed, it has also been shown, in very large series, that oesophagitis patients are at increased risk for laryngeal and pulmonary disease,9 this finding having been recently confirmed, in consecutive patients with suspected GORD-related ENT symptoms.10 At present, data concerning the association between the presence of erosive disease and proximal extent of gastric reflux are lacking.

Among the factors possibly involved in favouring proximal reflux, the role of oesophageal motor responses to reflux, either peristaltic contractions or oesophageal tone, is not fully understood. Changes in oesophageal tone and length might, theoretically, modulate the aboral progression of a bolus and the proximal extent of reflux. Interestingly, it has recently been shown that experimental acute oesophagitis increases oesophageal tone and provokes oesophageal shortening in cats.11 In keeping with the latter finding, intra-oesophageal acid perfusion, in humans, causes an inflammation-related contraction of the longitudinal muscle and oesophageal shortening.12

The aim of this study was to assess the proximal extent of reflux, both acid and weakly acidic, in GORD patients with and without oesophagitis and to confirm, using an animal model of GORD, the relationship between acute oesophagitis and proximal extent of gastric reflux.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Human study

Subjects

A total of 49 consecutive patients complaining of typical GORD symptoms – heartburn and/or acid regurgitation – lasting more than 6 months, were invited to take part in the study. All patients underwent upper endoscopy, stationary oesophageal manometry and 24-h pH-impedance monitoring, the latter performed 3–14 days (median 5 days) after endoscopy. Following upper endoscopy, five patients were excluded from the study because of duodeno-gastric peptic disease and/or Barrett oesophagus. Of the remaining 44 enrolled patients, 27 were NERD patients (16 men, median age 46 years, range 31–57), showing a favourable response to proton pump inhibitors (PPI) treatment (lasting ≤2 weeks) and no presence of erosive disease at previous endoscopy, 17 patients (11 men, median age 54 years, range 34–59) showed erosive oesophagitis (grade I n = 10, grade II n = 7, according to modified Savary–Miller classification). Hiatal hernia, defined as squamo-columnar junction ≥2 cm proximal to the hiatal impression, was present in 9 of 27 NERD patients and in 7 of 17 oesophagitis patients. PH-impedance data were compared with those of 10 asymptomatic, hospital staff volunteers (6 men, median age 34 years, range 31–47; healthy control group), all non-smokers.

None of the patients had undergone previous gastrointestinal surgery or was taking medication known to influence oesophageal motor function. Patients on antisecretory drugs stopped the medicament at least 2 weeks prior to the study. The study protocol was approved by the Ethics Committee of University Campus Bio Medico of Rome and written informed consent was obtained from all individuals.

Intraluminal electrical impedance and pH

Intraluminal electrical impedance was recorded with a 2.3-mm diameter polyvinyl assembly containing a series of cylindrical electrodes, each 4 mm in axial length, spaced at 2-cm intervals. Each pair of electrodes formed a measuring segment, 2 cm in length, corresponding to one recording channel (Sandhill Scientific Inc., Highlands Ranch, CO, USA). The signals from the impedance and pH channels were digitized at 50 Hz and stored in a separate data logger (Sandhill Scientific Inc.). Oesophageal pH was measured with an antimony pH electrode. Before the start and at the end of the recording, the pH electrodes were calibrated using pH 1.0 and pH 7.0 buffer solutions.

Patients and controls were studied after an overnight fast of at least 10 h. Prior to the ambulatory study, all subjects underwent stationary oesophageal manometry to locate the lower oesophageal sphincter (LOS). After the stationary manometry, the combined pH impedance assembly was passed through the nose under topical anaesthesia and positioned with the pH electrode at 5 cm above the LOS. In this position, impedance was measured at 3, 5, 7, 9, 15 and 17 cm proximal to the LOS. Patients and controls were asked to remain upright during the day, and to lie down only at their usual bedtime. Event markers, on the monitor, had recorded meal times and posture changes.

Data analysis

In the analysis of impedance tracings, liquid reflux was defined as a retrograde 50% drop in impedance starting distally (at the level of the LOS) and propagating to at least the next two more proximal impedance measuring segments. Mixed liquid–gas reflux was defined as gas reflux occurring immediately before or during a liquid reflux. Changes in oesophageal pH during reflux detected by impedance allowed classification of reflux in (i) acid reflux: refluxed gastric juice with a pH less than 4, which can either reduce the pH of the oesophagus to below 4 or occur when oesophageal pH is already below 4, (ii) weakly acidic reflux: reflux events that result in an oesophageal pH between 4 and 7, and weakly alkaline reflux (iii) Weakly alkaline reflux: reflux episodes during which nadir oesophageal pH does not drop below 7.13

During reflux, drops of impedance, in the mid- and upper oesophagus, indicated the proximal extent of the liquid refluxate. Drops of impedance that reached the distal measuring segment at 5 cm above LOS indicated a distal not-propagated event. The percentage of reflux episodes that reached the impedance segments in the mid-oesophagus (15 cm above LOS) and proximal oesophagus (17 cm above LOS) was calculated in patients and controls.

Statistical analysis

Data are expressed as mean ±standard deviation (SD). In the analysis of pooled data, the proportion of reflux events, acid and weakly acidic, which reached the proximal oesophagus in controls, NERD and oesophagitis patients, was compared using Fisher's exact test. A P value <0.05 was considered to be significant.

Experimental model of gastro-oesophageal reflux disease

Experimental studies were performed on five adult cats weighing 3–5 kg under light anaesthesia with ketamine chloride (Parke-Davis, NV Warner-Lambert, Zaventem, Belgium) at 15 mg kg−1 i.m. injection for induction and 10 mg kg−1 i.m., every 30–45 min, for maintenance.

The experimental protocol followed the Guiding Principles For Research Involving Animals described in the Declaration of Helsinki and was approved by the Ethics Committee for Experimental Animals of the Catholic University of Leuven, Belgium.

Gastro-oesophageal reflux simulation and recording assembly

An in vivo feline model was prepared to simulate gastro-oesophageal reflux episodes using a fast intra-oesophageal retrograde injection of a radiopaque solution at a fixed flow rate using an angiographic electronic pump.

The retrograde bolus injections were performed via a percutaneous endoscopic gastrostomy (PEG) (Flocare PEG Ch18F, Nutricia, Bornem, Belgium). The PEG was performed under light anaesthesia (ketamine 20 mg kg−1) and animals were allowed to recover for 7 days before the experimental procedures.

A polyvinyl injection tube (internal diameter, 1.5 mm; outer diameter, 3 mm) was placed via the gastrostomy with the tip located at the proximal margin of the manometrically determined LOS. Reflux events were simulated by fast retrograde injection of a radiopaque solution (1 mL) at a fixed flow rate (10 mL s−1) using an electronic pump (Medrad Inc., PA, USA) specially designed for cardiovascular/angiographic injection procedures. The reflux simulation experiments were performed with the animal's body and head elevated 30 °. A radiopaque metric ruler was placed lateral to the cat oesophagus.

Each reflux simulation event was recorded and the fluoroscopic video was digitized (25 frames s−1) for further analysis using a dedicated software for frame-to-frame analysis.

Experimental acute oesophagitis

Acute oesophagitis was induced by intraluminal acid perfusion of a solution 0.1 N HCl at 1.0 mL min−1 for 80 min at 1 cm above the manometrically identified LOS using a peristaltic pump. The degree of oesophageal mucosal damage was evaluated endoscopically (Olympus CF, type 1301, Japan) at 24 h. Buprenorphinum (Temgesic®; Schering-Plough, Brussels, Belgium) 0.3 mg day−1 was given as analgesic.

Study protocol

Reflux simulation experiments were performed before and 24 h after acid-perfusion-induced acute oesophagitis. Experiments were performed with three solutions of water-soluble radiographic contrast medium (Gastrografine, Schering, Auckland, New Zealand) of increasing viscosity containing 0%, 0.5% and 1% of metilcellulose (MC). The viscosity of each solution, measured in vitro at 38 ° (the normal body temperature of cat), was 1.98 mPas (0% MC), 8.66 mPas (0.5% MC) and 33.34 mPas (1% MC). The latter viscosity was comparable to that obtained from aspirated human gastric refluxate in the postprandial phase.

Data analysis

The proximal extent of simulated reflux was measured using a metric ruler between the proximal margin of the LOS (tip of injection catheter) and the most proximal oesophageal site reached by the bolus head (Fig. 1). The velocity of the simulated reflux was calculated from the time interval (seconds) between appearances of contrast at the proximal margin of LOS to the moment of maximal proximal extent and divided by the distance (cm) observed between these two points. The reproducibility of these parameters was tested in healthy cats. Reflux simulation with the three different viscous solutions was performed on three different days in each cat alternating the order of viscosities.

image

Figure 1.  Simulated gastro-oesophageal reflux. (A) Injection was performed at proximal margin of the LOS. (B) Proximal extent was 7 cm.

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Statistics

Values are expressed as means ± SEM. The differences in proximal extent and velocity of simulated reflux were compared using one-way analysis of variance followed by Dunn's multiple comparison test. The Student's t-test for paired data was used to compare these parameters before and after acute oesophagitis. A P value <0.05 was considered to be significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

Patients and controls

A total of 4428 reflux events were detected at distal oesophageal level: mean 31 (range 17–82) in the healthy controls; 73 (range 19–145) in NERD and 89 (range 25–176) in oesophagitis patients, P < 0.001. Weakly acidic reflux represented 55% of the total reflux events in healthy controls, 28% in NERD and 26% in patients with oesophagitis. Nearly two-thirds of weakly acidic reflux occurred during the postprandial periods; liquid–gas reflux accounted for 50–60% of reflux in all groups.

The dynamic characteristics of the reflux events in the NERD, oesophagitis patients and healthy controls are shown in Table 1. The patient groups showed a higher percentage of proximal reflux, both acid and weakly acidic, when compared with healthy controls. Considering all reflux events, the percentage of proximal reflux (at 17 cm above LOS) was 11% in healthy controls, 22% in NERD patients and 38% in oesophagitis patients (P < 0.05). Taking into consideration, the acidity of the refluxate, acid reflux showed higher proximal extent when compared with weakly acidic reflux in patients and controls.

Table 1.   Percentage of proximal extent of acid and weakly acidic reflux (mean ± SD)
 ControlsNERDOesophagitis
Total (%)Acid (%)Weakly acidic (%)Total (%)Acid (%)Weakly acidic (%)Total (%)Acid (%)Weakly acidic (%)
  1. *P < 0.05 vs weakly acidic, **P < 0.05 vs controls, ***P < 0.05 vs NERD.

15 cm above LOS27 ± 224 ± 2*17 ± 239 ± 2**44 ± 4*,**27 ± 5**59 ± 1**,***62 ± 3*,**,***45 ± 5**,***
17 cm above LOS11 ± 215 ± 3*7 ± 222 ± 1**29 ± 3*,**16 ± 4**38 ± 2**,***39 ± 3*,**,***23 ± 3**,***

Experimental model of gastro-oesophageal reflux disease: effects of acute oesophagitis on proximal extent and velocity of retrograde flow

Acid perfusion provoked severe oesophagitis with circumferential erosions, assessed by means of endoscopy, in the distal half of the oesophagus in all cats. Before oesophagitis, the proximal extent of solution with 0% MC was 6.2 ± 0.3 cm at a velocity of 5.5 ± 1.6 cm s−1 whereas the solution with 1% MC had a proximal extent of 4.5 ± 0.2 cm at a velocity of 1.0 ± 0.2 cm s−1 (P < 0.05). These parameters did not show significant difference between the three days (P = 0.1276). The proximal extent of simulated reflux during oesophagitis was higher than in healthy cats with the more viscous tested solution (1% MC: P < 0.05, vs before oesophagitis) (Fig. 2A). During oesophagitis, the velocities were slightly faster than in healthy cats (Fig. 2B).

image

Figure 2.  Effects of acute oesophagitis on proximal extent and velocity. (A) The proximal extent of different viscous solutions was higher during oesophagitis with the more viscous solution (*1% MC: P < 0.05, vs before oesophagitis). (B) Velocity of proximal extent was slightly faster following acute oesophagitis (NS).

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References

As far as concerned, the factors possibly involved in the proximal spread of reflux, data on the role of oesophagitis and on the characteristics of the refluxate are lacking. Data from the present study demonstrate that oesophagitis patients are characterized by a higher proximal extent of reflux, both acid and weakly acidic, compared with NERD patients and controls and that in the experimental model of GORD, acute oesophagitis does favour proximal migration of simulated reflux.

This finding, related to acid reflux, is in agreement with a previous multi-channel pH-study showing a higher perception of proximal reflux in NERD patients but a higher percentage of proximal acid reflux in oesophagitis compared with NERD patients and controls.2 We also assessed, for the first time and in a large series, the dynamic characteristics of weakly acidic, compared with acid, reflux: although weakly acidic reflux showed higher proximal extent in oesophagitis than in NERD patients and controls, it was less proximally propagated than acid reflux in all individuals.

Previous studies have underlined the relevance of proximal spread of the gastric refluxate on ENT manifestations of GORD patients and the higher risk of supra-oesophageal symptoms in the presence of erosive disease.9 In keeping with our findings of higher proximal spread of gastric refluxate in oesophagitis patients, a recent study, carried out in consecutive patients with suspected GORD-related ENT symptoms, showed a significantly higher rate of symptom relief following PPI treatment in the oesophagitis group compared with those without oesophagitis.10

Although it is conceivable that the higher proximal extent of reflux in oesophagitis patients is related to the higher volume of refluxate, the presence of acute oesophagitis is also associated with important changes in the oesophageal tone.11 In order to assess factors possibly affecting proximal extent of reflux, in the present study, we developed an experimental in vivo model of GORD to simulate reflux events under controlled circumstances. After inducing acute severe oesophagitis, refluxate of increasing viscosities was injected at the proximal margin of the LOS, at a fixed pressure and volume, with the animal in resting upright (30 °) position. It was thus possible to evaluate the effect of acute mucosal inflammation on the proximal extent of reflux which was found to be significantly increased during acute oesophagitis. Possible explanations for this finding could be: (i) oedema associated with severe inflammation that might lead to a narrower oesophageal lumen favouring a higher proximal extent; (ii) increased oesophageal tone and oesophageal shortening with impaired distension-induced distal oesophageal accommodation and (iii) impaired primary and secondary peristalsis during severe mucosal inflammation.

Indeed, severe ineffective oesophageal motility may be caused by various conditions and is strongly associated with the presence of erosive disease.14

It has also been demonstrated that, in cats, acute experimental oesophagitis induces severe oesophageal motor dysfunction together with increased resting oesophageal tone, decreased oesophageal compliance and shortening of oesophageal length.11,12 These changes might explain the enhancing role of oesophagitis on the proximal extent of reflux.

Our experimental model of GORD also showed that high-viscosity refluxate significantly decreases the proximal extent of simulated reflux, maximally in the absence of acute inflammation, whereas it reduces the ascending velocity of retrograde flow both before and after acute oesophagitis. Frictional resistance may account for the lower proximal extent of the more viscous solution. Another possible explanation could be the different intraluminal distribution of the refluxate due to an adaptive motor response. Distension of the oesophagus, assessed by ultrasound as changes in the cross-section area, linearly increases with the increase in swallowed bolus volumes, the distal oesophagus appearing to be the most compliant oesophageal segment.15 It might be hypothesized that high viscous solutions, due to the slower transit, would provoke a greater and longer lasting distension of the very distal oesophagus. This distension might induce relaxation at that level16 with pooling of liquid more distally, resulting in reduced maximal proximal extent. Future studies assessing the viscosity of weakly acidic reflux, likely more viscous than acid reflux, could clarify the role, if any, of physical characteristics of refluxate on its intra-oesophageal distribution. It should be taken into consideration that our model of acute oesophagitis could differ from the chronic repetitive insult in oesophagitis patients; nevertheless, the animal setting could help to explain the effect of inflammation on proximal extent of reflux.

In conclusion, our study demonstrates that oesophagitis patients are characterized by a higher proximal oesophageal extent of reflux, both acid and weakly acidic, when compared with NERD patients and controls and that acute oesophagitis appears to favour proximal migration of simulated reflux.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. References
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