The importance of gastric emptying in reflux esophagitis: an experimental research on pigs

Effect of reflux and esophagitis on esophageal volume and acid clearance in piglets

BACKGROUND/AIMS

The study investigates esophageal motor function and esophageal clearance immediately after surgical induction of reflux in piglets and 8 weeks later after peptic esophagitis has developed.

METHODS

Twenty-four sedated, nonintubated piglets were divided into three groups: sham (laparotomy only), reflux (distal esophageal myotomy), and reflux + esophagitis (8 weeks after myotomy). All animals underwent stationary manometry of the esophagus with a four-lumen perfused assembly after injection of 1-, 2-, and 3-mL boluses of saline and acid into the proximal esophagus. Simultaneous pH monitoring allowed assessment of acid clearance. Wave features and clearance times after saline and acid were compared among groups.

RESULTS

There were minor changes in peristaltic activity of the esophagus after saline boluses in animals with reflux. Acid clearance time was prolonged, especially the time to re-establish resting esophageal pH, in animals with esophagitis. These changes, which were volume-dependent, were related to the loss of peristaltic organization of the esophageal waves. The esophageal wave frequency, amplitude, and duration were only slightly changed by the induction of reflux and by esophagitis.

CONCLUSIONS

The esophagus affected by acid reflux, with or without esophagitis, was capable of near-normal motor responses after boluses of saline. Reflux impaired the peristaltic response to acid, and the effect was more pronounced when reflux and esophagitis were both present. The acid clearance time was also strikingly prolonged in the presence of reflux and esophagitis. The results suggest that long episodes of reflux seen on pH tracings from individuals with esophagitis might be secondary both to acid-related motor dysfunction and large volumes of refluxate.

Ambulatory long-term pH monitoring in pigs

BACKGROUND

pH monitoring has been established as the "gold standard" in the diagnosis of gastroesophageal reflux. Evaluation of experimental antireflux therapy should therefore also include this technique, but a suitable technique in an experimental model did not exist so far. The aim of our study was to establish a reliable method for the evaluation of an experimental reflux model in pigs.

METHODS

A total of 33 German Landrace pigs with an average body weight of 56 (50.2-67.2) kg were included. pH monitoring was performed before and after open cardiomyotomy in each animal. All manipulations were performed under general anesthesia. After manometric localization of the gastroesophageal high-pressure zone, a standard pH probe was inserted into the pharynx through a small needle-punctured canal on the side of the animal's snout and placed under endoscopic guidance with the proximal sensor 3 cm above the lower esophageal sphincter (LES) and the distal sensor in the stomach for reference. The harness to carry the pH recorder on the animal's back consisted of a modified belly strap that enabled the animal to move around without limitation. For analysis the same threshold levels were defined as in humans. Gastroesophageal reflux was induced by cardiomyotomy.

RESULTS

The placement of the standard pH probe was possible in all cases. Inserting the probe on the side of the snout left the animals free to nuzzle, which complies with the normal habits of pigs, without breaking the probes and without being compromised in their natural behavior. Repeated punctures for multiple measurements were easily feasible. We performed up to three examinations in each individual animal. Recording was performed for 48 h. A mean number of 67.3 (+/-9.7) acidic refluxes were registered. The mean number of long acidic refluxes was 3.2 (+/-0.75). For an average total time of 75.5 (+/-14.3) min the pH was below 4 accounting for a fraction time pH below 4 of 3.5% (+/-0.68%). Following cardiomyotomy the number of acidic refluxes increased significantly to 166.1 (+/-21.8) and the number of long refluxes to 17.74 (+/-3.35). The total time of pH below 4 increased to 371.3 (+/-62) min so that the fraction time pH below 4 was 14.5% ( p = 0.0006).

CONCLUSION

pH monitoring should be mandatory in any investigation of antireflux therapy. Our method is easy and secure to perform. It is suitable for other gastrointestinal investigations (Bilitec, long-term manometry) that could be carried out using the same technique. The described data represent the basis for other investigations of experimental antireflux therapy.

Individual inactivation of the sphincteric component of the gastroesophageal barrier causes reflux esophagitis in piglets

BACKGROUND/PURPOSE

The lower esophageal sphincter and the diaphragmatic crural sling form the gastroesophageal barrier. This work shows that division of the sphincteric component alone suffices to induce reflux esophagitis in piglets.

METHODS

Male piglets underwent either sham operation (n = 7) or extramucosal myotomy of the gastroesophageal junction (n = 8). Before and 1 week after the operation, pull-through manometry was performed under sedation. Pressures taken on the 4 quadrants at 20 1-mm intervals on both time endpoints were compared by pairwise Wilcoxon tests. The distal esophagus was studied histologically after 8 weeks.

RESULTS

The pressure profiles did not change after sham operation. In contrast, they were significantly flattened in the distal half of the high-pressure zone after myotomy reflecting disappearance of the sphincteric component of the barrier. Esophagitis was seen in all myotomized piglets but in none from the sham group.

CONCLUSIONS

Lower esophageal sphincter myotomy alone with preservation of the crural sling induces reflux esophagitis in piglets. This animal, widely available and not too costly, is an excellent model for gastroesophageal research.

Experimental esophagitis induced by acid and pepsin in rabbits mimicking human reflux esophagitis

BACKGROUND & AIMS

The lack of appropriate animal models might explain the paucity of information on the mechanisms of mucosal damage and defense in reflux esophagitis. The aim of this study was to develop a model of esophagitis in rabbits mimicking human reflux esophagitis.

METHODS

New Zealand white rabbits underwent surgery for placement of a plastic tube into the cervical esophagus. Acidified pepsin (AP) was intermittently perfused for different periods. Esophageal injury was assessed by macroscopic and microscopic examination, including the cell proliferation immunohistochemical parameter mib1.

RESULTS

Rabbit losses (20%) were attributable mostly to postsurgical mortality and tube displacement. Perfusion of AP for 60 min/12 h or 45 min/12 h induced high-grade esophagitis by days 3 and 5, respectively, characterized by diffuse erosion/ulceration, inflammation, bleeding, and reactive epithelial changes. Perfusion of acidified pepsin for 60 min/day, especially at 30 min/12 h, induced low-grade esophagitis characterized by superficial epithelial loss, mild/absent inflammation, and epithelial reactive changes including increased cell proliferation, basal hyperplasia, and papillomatosis, which reached maximal expression by day 7. This perfusion regimen induced mucosal adaptation to damage.

CONCLUSIONS

Different and highly reproducible esophageal mucosal lesions mimicking human reflux esophagitis can be induced in rabbits with repetitive acid and pepsin exposure.