A porcine model of gastroesophageal reflux

Arecae pericarpium extract induces porcine lower-esophageal-sphincter contraction via muscarinic receptors

Background

Gastroesophageal reflux disease (GERD) is associated with lower esophageal sphincter (LES) incompetence. In some patients, GERD is refractory to acid reduction therapy which is the main treatment for GERD. So far, medications that can increase LES tone are few. Arecae pericarpium (A. pericarpium) is a medication in Traditional Chinese Medicine known to promote intestinal motility.

Methods

We investigated the effect of A. pericarpium extracts on porcine LES motility. In addition, we used tetrodotoxin (TTX) and atropine to study the underlying mechanism of A. pericarpium extracts-induced contractions of LES.

Results

The results of this study showed that A. pericarpium extracts and their main active ingredient, arecoline, can induce the contractions of porcine LES sling and clasp muscles in a dose-response manner. TTX did not have an inhibitory effect on the contractions induced by A. pericarpium extracts and arecoline in LES. However, atropine significantly inhibited A. pericarpium extracts- and arecoline-induced contractions of LES.

Conclusion

A. pericarpium extracts can induce the contractions of porcine LES in a dose dependent manner, possibly through muscarinic receptors, and hence, may be worth developing as an alternative therapy for GERD.

Long-Chain Fatty Acid Receptors Mediate Relaxation of the Porcine Lower Esophageal Sphincter

Long-chain fatty acids activate the free fatty acid receptor 1 (FFA1) and FFA4. In the gastrointestinal system, FFA1 and FFA4 have been found in the pancreas and intestine. Fatty food and decreased lower esophageal sphincter (LES) motility are associated with gastroesophageal reflux disease. The effect of long-chain fatty acids on the esophageal motility is unknown. The purpose of this study is to investigate the effects of long-chain fatty acids on the porcine LES motility ex vivo using isometric transducers. In endothelin 1-precontracted porcine LES strips, the FFA1 selective agonists, fasiglifam, TUG424, and GW9508, caused marked relaxations in a concentration-dependent manner. The relative efficacies to elicit relaxation were GW9508 > TUG424 > fasiglifam in both clasp and sling strips. In contrast, the FFA4 specific agonists, TUG891 and GSK137647, produced mild relaxations. In addition, the endogenous FFA1 agonist DHA caused a mild relaxation whereas GW1100, an FFA1 antagonist, inhibited GW9508 induced relaxation of the porcine LES clasp and sling muscle. Both real-time PCR and immunohistochemistry revealed that FFA1 and FFA4 were expressed in the porcine LES. Real-time PCR analysis showed that the FFA4 expression was much lower than FFA1. Taken together, long-chain fatty acid receptor agonists elicit relaxation of the porcine LES. FFA1 might influence LES motility.

Trypsin induces biphasic muscle contraction and relaxation via transient receptor potential vanilloid 1 and neurokinin receptors 1/2 in porcine esophageal body

Duodenal reflux of fluids containing trypsin relates to refractory gastroesophageal reflux disease (GERD). Esophageal peristalsis and clearance are important factors in GERD pathogenesis. However, the function of trypsin in esophageal body contractility is not fully understood. In this study, effects of trypsin on circular smooth muscle (CSM) and longitudinal smooth muscle (LSM) of the porcine esophageal body were examined. Trypsin elicited a concentration dependent biphasic response, a major contraction and a subsequent relaxation only in CSM. In CSM, contraction occurred at trypsin concentrations of 100nM and relaxation at 1μM. A proteinase-activated receptor (PAR)2 activating peptide, SLIGKV-NH₂ (1mM), induced a monophasic contraction. Those responses were unaffected by tetrodotoxin though abolished by the gap junction uncouplers carbenoxolone and octanol. They were also partially inhibited by a transient receptor potential vanilloid type 1 (TRPV1) antagonist and abolished by combination of neurokinin receptor 1 (NK₁) and NK₂ antagonists, but not by an NK₃ antagonist, suggesting a PAR2-TRPV1-substance P pathway in sensory neurons. Substance P (100nM), an agonist for various NK receptors (NK₁, NK₂ and NK₃) with differing affinities, induced significant contraction in CSM, but not in LSM. The contraction was also blocked by the combination of NK₁ and NK₂ antagonists, but not by the NK₃ antagonist. Moreover, substance P-induced contractions were unaffected by the TRPV1 antagonist, but inhibited by a gap junction uncoupler. In conclusion, trypsin induced a biphasic response only in CSM and this was mediated by PAR2, TRPV1 and NK_1/2. Gap junctions were indispensable in this tachykinin-induced response.

Mechanism of bombesin-induced tonic contraction of the porcine lower esophageal sphincter

Gastroesophageal reflux disease (GERD) is a disorder that is related to an incompetent lower esophageal sphincter (LES). Previous studies showed that bombesin could increase LES pressure in humans and opossums. The aim of the present study was to characterize the effects of bombesin on porcine LES contraction. We used the selective agonists, neuromedin B (NMB), gastrin-releasing peptide (GRP), and [D-Tyr⁶,Apa-4Cl¹¹,Phe¹³,Nle¹⁴]bombesin-(6-14) (DTACPN-BN), as well as receptor antagonists of bombesin receptor subtype 2 (BB₂), and 3 (BB₃) for ex vivo contraction studies. Atropine, nifedipine, tetrodotoxin, and ω-conotoxin GVIA were used to explore the agonist-induced LES contraction mechanism. Reverse transcription polymerase chain reaction and immunohistochemistry were applied to detect bombesin receptor expression. Our results indicate that GRP and DTACPN-BN, but not NMB, induced tonic contractions of the porcine LES in a dose-dependent manner, and the contractions were inhibited with selective BB₂ and BB₃ antagonists. The GRP-induced contraction is mainly caused by L-type Ca²⁺ channel-mediated Ca²⁺ influx. However, DTACPN-BN-induced contractions are associated with neuronal conduction. RT-PCR and immunohistochemistry revealed that BB₂ and BB₃ were expressed in the porcine LES. Bombesin-induced tonic contraction of the LES is mediated through BB₂ and BB₃. Bombesin, BB_2, and BB₃ agonists might have the potential to treat GERD.

Lower esophageal sphincter augmentation by endoscopic injection of dextranomer hyaluronic acid copolymer in a porcine gastroesophageal reflux disease model

BACKGROUND

We previously demonstrated feasibility, safety, and a reproducible histologic bulking effect after injection of dextranomer hyaluronic acid copolymer (DxHA) into the gastroesophageal junction of rabbits. In the current study, we investigated the potential for DxHA to augment the lower esophageal sphincter (LES) in a porcine model of gastroesophageal reflux disease (GERD).

METHODS

Twelve Yucatan miniature pigs underwent LES manometry and 24-hour ambulatory pH monitoring at baseline, after cardiomyectomy, and 6weeks after randomization to endoscopic injection of either DxHA or saline at the LES. After necropsy, the foregut, including injection sites, was histologically examined.

RESULTS

Pigs in both groups had similar weight progression. Cardiomyectomy induced GERD in all animals, as measured by a rise in the median % of time pH <5 from 0.6 to 11.6 (p=0.02). Endoscopic injection of DxHA resulted in a higher median difference in LES length (1.8cm vs. 0.4cm, p=0.03). In comparison with saline injection, DxHA resulted in 120% increase in LES pressure, and 76% decrease in the mean duration of reflux episodes, but these results were not statistically significant. Injection of DxHA induced a foreign body reaction with fibroblasts and giant cells.

CONCLUSIONS

Porcine cardiomyectomy is a reproducible animal GERD model. Injection of DxHA may augment the LES, offering a potential therapeutic effect in GERD.

Gastric yield pressure and gastric yield volume to assess anti-reflux barrier in a porcine model

Anti-reflux barrier (ARB) resistance may be useful to test new treatments for gastroesophageal reflux (GER). The ARB has been estimated by increasing gastric yield pressure (GYP) and gastric yield volume (GYV) in animal models but has not been validated. This study aimed to develop an experimental model suitable for assessing the ARB resistance to increasing intragastric pressure and volume and its reproducibility in a seven-day interval. Ten two-month-old female Large-White swine were studied. Intragastric pressure and volume were recorded using a digital system connected to a Foley catheter inserted through gastrostomy into the stomach. GYP and GYV were defined as the gastric pressure and volume able to yield gastric contents into the esophagus detected by esophageal pH. A sudden pH drop below 3 sustained during 5 min was considered diagnostic for gastric yield. Animals were studied again after seven days. On days 0 and 7, there were no significant differences for GYP (mean ± SD = 7.66 ± 3.02 mmHg vs. 7.07 ± 3.54 mmHg, p = .686) and GYV (636.70 ± 216.74 ml vs. 608.30 ± 276.66 ml; p = .299), respectively. Concordance correlation coefficient (ρc) was significant for GYP (ρc = 0.634, 95% CI = 0.141-0.829, p = .006), but not for GYV (ρc = 0.291, 95% CI = -0.118 to 0.774, p = .196). This study demonstrated an experimental model, assessing the ARB resistance. GYP seems to be a more reliable parameter than GYV for assessment of ARB resistance.

Response of cricopharyngeus muscle to esophageal stimulation by mechanical distension and acid and bile perfusion

OBJECTIVES

The aim of this study was to identify the response of the cricopharyngeus muscle (CPM) to esophageal stimulation by intraluminal mechanical distension and intraluminal acid and bile perfusion.

METHODS

In 3 adult pigs, electromyographic (EMG) activity of the CPM was recorded at baseline and after esophageal stimulation at 3 levels: proximal, middle, and distal. The esophagus was stimulated with 20-mL balloon distension and intraluminal perfusion of 40 mL 0.1N hydrochloric acid, taurocholic acid (pH 1.5), and chenodeoxycholic acid (pH 7.4) at the rate of 40 mL/min. The EMG spike density was defined as peak-to-peak spikes greater than 10 microV averaged over 10-ms intervals.

RESULTS

In all 3 animals, the spike density at baseline was 0. The spike densities increased after proximal and middle distensions to 15.2 +/- 1.5 and 5.1 +/- 1.2 spikes per 10 ms, respectively. No change in CPM EMG activity occurred after distal distension. The spike density following intraluminal perfusion with hydrochloric acid at the distal level was 10.1 +/- 1.1 spikes per 10 ms. No significant change in CPM EMG activity occurred after acid perfusion at the middle and proximal levels. No change in CPM EMG activity occurred after intraluminal esophageal perfusion with either taurocholic acid or chenodeoxycholic acid.

CONCLUSIONS

Proximal esophageal distension, as well as distal intraluminal acid perfusion, appeared to be important mechanisms in generation of CPM activity. Bile acids, on the other hand, failed to evoke such CPM activity. The data suggest that transpyloric refluxate may not be significant enough to evoke the CPM protective sphincteric function, thereby placing supraesophageal structures at risk of bile injury.

Comparison of human and porcine gastric clasp and sling fiber contraction by M2 and M3 muscarinic receptors

To compare the gastroesophageal junction of the human with the pig, M(2) and M(3) receptor densities and the potencies of M(2) and M(3) muscarinic receptor subtype selective antagonists were determined in gastric clasp and sling smooth muscle fibers. Total muscarinic and M(2) receptors are higher in pig than human clasp and sling fibers. M(3) receptors are higher in human compared with pig sling fibers but lower in human compared with pig clasp fibers. Clasp fibers have fewer M(3) receptors than sling fibers in both humans and pigs. Similar to human clasp fibers, pig clasp fibers contract significantly less than pig sling fibers. Analysis of the methoctramine Schild plot suggests that M(2) receptors are involved in mediating contraction in pig clasp and sling fibers. Darifenacin potency suggests that M(3) receptors mediate contraction in pig sling fibers and that M(2) and M(3) receptors mediate contraction in pig clasp fibers. Taken together, the data suggest that both M(2) and M(3) muscarinic receptors mediate the contraction in both pig clasp and sling fibers similar to human clasp and sling fibers.

Workflow analysis of laparoscopic Nissen fundoplication in infant pigs- a model for surgical feedback and training

BACKGROUND

Many fields use workflow analysis to assess and improve performance of complex tasks. In pediatric endosurgery, workflow analysis may help optimize operative planning and motor skills by breaking down the procedure into particular phases, evaluating these steps individually, and supplying feedback to the surgeon.

OBJECTIVE

To develop a module of computer-based surgical workflow analysis for laparoscopic Nissen fundoplication(LNF) and to evaluate its applicability in an infant pig model.

METHODS

LNF was performed in 12 pigs (weight, 7-10 kg) by a single surgeon. Based on synchronized intra and extracorporal movie recordings, the surgical workflow was segmented into temporal operative phases(preparation, dissection, reconstruction and conclusion). During each stage, all actions were recorded in a virtual timeline using a customized workflow editor. Specific tasks, such as knot-tying, were evaluated in detail.Time necessary to perform these actions was compared throughout the study.

RESULTS

While time required for the preparation decreased by more than 70% from 4577 to 1379 seconds,and the dissection phase decreased from 2359 to 399 seconds (pig 1 and 12, respectively), the other two phases remained relatively stable. Mean time to perform the entire suture and a 5-throw knot remained constant as well.

CONCLUSION

Our workflow analysis model allows the quantitative evaluation of dynamic actions related to LNF.This data can be used to define average benchmark criteria for the procedures that comprise this operation. It thereby permits task-oriented refinement of surgical technique as well as monitoring the efficacy of training.Although preoperative preparation time decreased substantially, and dissection became faster, time required for the reconstruction and conclusion phases remained relatively constant for a surgeon with moderate experience.Likewise, knot-tying did not accelerate in this setting.S-117

Workflow analysis of laparoscopic Nissen fundoplication in infant pigs- a model for surgical feedback and training

BACKGROUND

Many fields use workflow analysis to assess and improve performance of complex tasks. In pediatric endosurgery, workflow analysis may help optimize operative planning and motor skills by breaking down the procedure into particular phases, evaluating these steps individually, and supplying feedback to the surgeon.

OBJECTIVE

To develop a module of computer-based surgical workflow analysis for laparoscopic Nissen fundoplication(LNF) and to evaluate its applicability in an infant pig model.

METHODS

LNF was performed in 12 pigs (weight, 7-10 kg) by a single surgeon. Based on synchronized intra and extracorporal movie recordings, the surgical workflow was segmented into temporal operative phases(preparation, dissection, reconstruction and conclusion). During each stage, all actions were recorded in a virtual timeline using a customized workflow editor. Specific tasks, such as knot-tying, were evaluated in detail.Time necessary to perform these actions was compared throughout the study.

RESULTS

While time required for the preparation decreased by more than 70% from 4577 to 1379 seconds,and the dissection phase decreased from 2359 to 399 seconds (pig 1 and 12, respectively), the other two phases remained relatively stable. Mean time to perform the entire suture and a 5-throw knot remained constant as well.

CONCLUSION

Our workflow analysis model allows the quantitative evaluation of dynamic actions related to LNF.This data can be used to define average benchmark criteria for the procedures that comprise this operation. It thereby permits task-oriented refinement of surgical technique as well as monitoring the efficacy of training.Although preoperative preparation time decreased substantially, and dissection became faster, time required for the reconstruction and conclusion phases remained relatively constant for a surgeon with moderate experience.Likewise, knot-tying did not accelerate in this setting.S-117

Improved reflux monitoring in the acute gastroesophageal reflux porcine model using esophageal multichannel intraluminal impedance measurement

BACKGROUND

Acute animal models are needed to obtain further insights into the mechanism of gastroesophageal reflux disease. Existing acute models use imprecise methods to detect reflux. The aim of the present study was to evaluate the potential of esophageal multichannel intraluminal impedance measurement (MII) to improve the quality of results of acute reflux porcine models.

MATERIALS AND METHODS

MII was used in ten pigs to monitor gastroesophageal reflux. Measurements were obtained (A) before and (B) after mobilization of the esophagus and (C) after myotomy. The results were compared to those obtained when reflux was monitored by esophageal drainage of intragastrically infused blue solution (DBS).

RESULTS

The times to first appearance of reflux were 67% (A), 86% (B), and 57% (C) of those by DBS when detected by MII; p < 0.05. The respective values for intragastric pressures needed to provoke reflux were 46%, 76%, and 66%; p < 0.05. Although the lower esophageal sphincter pressure decreased by 69% after (B) the intragastric pressure needed to provoke reflux increased by 140%; p < 0.05.

CONCLUSIONS

MII improves the detection of reflux in the acute reflux porcine model. The finding that after sole mobilization of the esophagus the intragastric pressure needed to provoke reflux was increased although the finding that the pressure of the lower esophageal sphincter was decreased needs further investigation.

Gastroesophageal reflux disease in baboons (Papio sp.): a new animal model

BACKGROUND

Gastroesophageal reflux disease (GERD) is increasingly prevalent in the human population. Current animal models require surgical or other manipulation to produce symptoms. An animal model that exhibits spontaneous GERD would provide the opportunity for much-needed research examining the susceptibility, diagnosis, and treatment of GERD.

METHODS

Eight baboons (Papio hamadryas sp.) were diagnosed with GERD histopathologically using biopsies or postmortem tissues.

RESULTS

The disease was characterized by a spectrum of symptoms comparable with that found in the human population. Some subjects had no gross signs of clinical disease, but were diagnosed by histopathological examination. Almost all subjects presented with at least one clinical sign of the disease. Regurgitation was the most common.

CONCLUSIONS

The baboon may be a superior animal model for GERD research because it is a naturally occurring model and is anatomically and physiologically similar to humans.

Mechanisms controlling function in the clasp and sling regions of porcine lower oesophageal sphincter

BACKGROUND

Characterization of functional differences between lower oesophageal sphincter (LOS) clasp and sling muscles might aid the development of more specific pharmacological and surgical approaches for the treatment of motility disorders.

METHODS

Circular LOS strips from 25 adult pigs were studied in organ baths to compare the physiology of clasp and sling fibres.

RESULTS

Sling strips developed greater tone than clasp fibres (mean(s.e.m.) 7.59(0.89) versus 4.72(0.67) g; P = 0.017). LOS tone was more dependent on extracellular calcium in clasp strips and on the activity of cholinergic enteric motor neurones (EMNs) in sling strips. The amplitude of maximal relaxation caused by electrical field stimulation (EFS, 3Hz) of EMNs was greater in clasp strips (mean(s.e.m.) 74.5(2.3) versus 58.1(2.2) per cent of tone; P < 0.001). EFS-induced relaxation was reduced in clasp fibres and fully blocked in sling fibres by nitrergic blockade with 10 micromol/l 1H-[1,2,4]oxadiazole-[4,3-alpha]quinoxalin-1-one (ODQ). The amplitude of EFS cholinergic responses was significantly greater in sling fibres. In the clasp region, relaxation caused by stimulation of EMNs with 100 micromol/l nicotine was reduced by ODQ. In sling fibres, nicotine induced relaxation at rest and cholinergic contraction following ODQ.

CONCLUSION

Clasp and sling fibres of the porcine LOS show marked intrinsic functional differences. This should be considered when developing more specific approaches to human LOS motility disorders.

Laparoscopic partial myectomy

BACKGROUND

A number of different surgical procedures have been described for the treatment of gastroesophageal reflux disease. Moreover, modifications and completely new techniques are being introduced on a regular basis. Nonetheless, in most cases of novel laparoscopic techniques profound experimental data have not been collected prior to their clinical introduction. Due to the lack of an animal model of inadequate esophageal sphincter function, most experimental studies on antireflux procedures were done on normally functioning esophageal sphincters.

METHODS

It is well-known that myotomy alone cannot induce sphincter insufficiency in animal models. In addition, complete myectomy is associated with severe mortality and, therefore, is not useful as an experimental model. This study introduces a new model of laparoscopic partial in vivo myectomy. The procedure described here forms a myectomy of the esophagus using scissors and a sponge on the side of the greater gastric curvature. The size of the myectomy is approximately 6 x 1.5 cm and was successfully performed in a consecutive series of eight experimental animals (male German house pigs).

RESULTS

Following an intensive team training on dead animals, the procedure was performed with success via the laparoscope in all study animals (n = 8). The sphincter pressure as determined by manometry was significantly reduced from 7.7 mmHg (range, 4.5-9.1; preoperative values) to 2.2 mmHg (range, 0-6.8; early postoperative values) and 2.3 mmHg (range, 0-3.7) at 8 weeks after surgery (p < 0.001). In addition, the length of the lower esophageal sphincter as well as the sphincter pressure vector volume were significantly reduced early as well as at 8 weeks after laparoscopic myectomy. Furthermore, endoscopy and reflux testing were pathologic compared with control animals.

CONCLUSIONS

Laparoscopic partial myectomy results in complete sphincter insufficiency with only little procedure-related morbidity. This procedure allows for the experimental evaluation of surgical procedures on the gastroesophageal junction. Future modifications of surgical antireflux procedures can therefore be evaluated in an experimental setting prior to their clinical introduction.

Responses of human clasp and sling fibers to neuromimetics

BACKGROUND AND AIMS

It has previously been demonstrated that clasp and sling fibers at the human gastroesophageal junction respond differently to acetylcholine (Ach). The present study was undertaken to investigate the differences between the physiological and pharmacological properties of the two types of muscle fiber.

METHODS

Recordings were made of the isometric tension of human sling and clasp fibers in response to Ach, dopamine (DA), phenylephrine (Phe), and isoprenaline (Iso). These specimens were obtained from 18 patients who were operated on for esophageal cancer.

RESULTS

Both Ach and Phe increased the tension of the two types of muscle; the values in the Ach group being 3-4-fold greater than those in the Phe group, while Iso decreased the tension of both types of muscle strip. The tension of the sling fibers was reduced by DA at lower concentration, and then increased gradually as the concentration was increased. In contrast, the tension of the clasp fibers did not obviously change when the concentration of DA was lower, but a slow elevation of tension was seen with the increase in DA concentration.

CONCLUSIONS

The sensitivities and maximum responses to each agent differed between the clasp fibers and sling fibers. This suggests that the two kinds of fiber have different roles in establishing tension in the lower esophageal sphincter, with implications for the medical and surgical treatment of disorders in this region.

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.

Endoluminal methods of treating gastroesophageal reflux disease

Several endoluminal methods of treating gastroesophageal reflux disease (GERD) have either been approved, or are under investigation and development. This review outlines the two approved methods (Bard's endoluminal sewing machine and Curon's Stretta radiofrequency treatment), and describes the available data on new methods under investigation. The various methods can be divided into three broad categories: methods that create a controlled stricture, methods that bulk the gastroesophageal junction, and methods that attempt to create a fundoplication. The pros and cons of each method are discussed. Unlike medical treatment, these methods attack the reflux itself, not just the symptoms. This is a promising approach. However, the controlled stricture and bulking methods do not approach the success rate of a standard fundoplication.

Plexiglas (polymethylmethacrylate) implantation: technique, pre-clinical and clinical experience

Over the past few decades, a great scientific effort has been made to treat gastroesophageal reflux disease (GERD). This reflects a trend in modem medicine toward optimizing quality of life, reducing health-related lost working hours, and minimizing costs of chronic treatments. It also reflects a revived interest in diseases that can be studied using novel equipment and that can be cured using minimally invasive techniques. In an effort to further minimize surgical trauma, novel endoscopic techniques are beginning to challenge the standard therapeutic approach to GERD.

Esophageal Acid clearance: more volume-dependent than motility-dependent in healthy piglets

BACKGROUND/AIMS

The present study investigates manometrically in healthy piglets whether esophageal clearance after distension with different volumes of acid is volume-dependent.

METHODS

Sedated, non-intubated piglets (n = 22) underwent stationary manometry of the esophagus with a 4-probe perfused assembly after successive injection of 1, 2, and 3 mL of saline and acid. Simultaneous pH metering allowed assessment of acid clearance. Wave features and clearance times after saline and acid were compared by paired non-parametric tests and Friedman analysis of variance. The linearity of the relationships between the clearance times and the volumes of acid infused were tested after square root transformations by one-way ANOVA repeated measures. The significance level was set at < 0.05.

RESULTS

The motor response was identical after distension with saline and acid except for the largest amount of acid used, which elicited more waves during the first 5 minutes after infusion. Time elapsed until regaining pH4 was longer after higher amounts of acid, but not significantly, whereas that necessary to regain baseline pH was significantly longer after such challenge. Esophageal motility was practically identical after 1 and 2 mL of acid, but it was slightly less effective in the first minute after the 3 mL challenge. There was a linear correlation between clearance times and volumes of acid infused.

CONCLUSIONS

Up to a certain volume, the motor responses of the healthy esophagus to distension with neutral or acid fluids were similar. Acid clearance was more a function of the amount of acid present than of the motor response elicited by its presence. Only when the amount of acid was large, esophageal motor response was worse than that elicited after equivalent volumes of neutral fluid. The present evidence suggests that long episodes of reflux in pH tracings might reflect large volumes of refluxate as well as disturbed motor function.

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.

Augmentation of lower esophageal sphincter pressure and gastric yield pressure after radiofrequency energy delivery to the gastroesophageal junction: a porcine model

BACKGROUND

An endoscopic technique that eliminates gastroesophageal reflux disease would be of benefit to patients. The endoscopic delivery of radiofrequency energy to the porcine gastroesophageal junction was investigated and its effect on lower esophageal sphincter pressure, gastric yield pressure, and histology was assessed.

METHODS

Twenty pigs underwent esophageal manometry and endoscopic injection of botulinum toxin (100 units) into the lower esophageal sphincter. After 1 week, animals were randomized to radiofrequency energy treatment of the gastroesophageal junction with a 4- needle catheter and thermocouple-controlled generator (n = 13) or no further intervention (control, n = 7). At 9 weeks, animals underwent esophagoscopy, manometry, gastric yield pressure determination, and sacrifice for histopathologic evaluation.

RESULTS

Mean lower esophageal sphincter pressure declined by 3.7 +/- 2.6 mm Hg (control, p = 0.03) vs. 0.97 +/- 5.8 mm Hg (radiofrequency, p = 0.29) after 9 weeks. Mean gastric yield pressure was 24.9 +/- 8.2 mm Hg (control), compared with 43.4 +/- 10. 7 mm Hg (radiofrequency) (p = 0.0007). Histopathologic assessment demonstrated normal mucosa, mild fibrosis, and no inflammation.

CONCLUSIONS

Radiofrequency energy delivery reversed much of the lower esophageal sphincter pressure reduction achieved with botulinum toxin injection and augmented gastric yield pressure by 75% compared with controls. Given the safety of radiofrequency energy delivery in this study and in other areas of medicine, human studies to assess the effect of radiofrequency energy on gastroesophageal reflux disease are warranted.

Gastroesophageal reflux after combined lower esophageal sphincter and diaphragmatic crural sling inactivation in the rat

This study tests the hypothesis that either selective or combined destruction of the lower esophageal sphincter and the diaphragmatic crural sling should induce reflux in the rat. Pull-through perfusion manometry was performed before and after lower esophageal myectomy, crural myotomy, or both. pH monitoring was used to detect reflux. Unmanipulated rats served as controls. Paired t tests were used for comparison of pre- and postoperative pressure values and contingency tables with Fisher's tests for examining the association between the interventions and the appearance of reflux. Esophageal myectomy decreased only sphincteric pressure from 25.9+/-15.5 to 9+/-6 mm Hg (P < 0.01), whereas crural myotomy decreased only sling pressure from 26.2+/-13.3 to 7.3+/-3.9 mm Hg (P < 0.01). Simultaneous performance of both procedures decreased sphincteric and crural pressures from 20.4+/-7.5 to 7.6+/-4.3 mm Hg (P < 0.01) and from 45.9+/-20.6 to 18.2+/-7.4 mm Hg (P < 0.01), respectively. None of the control, myectomy, or myotomy animals showed reflux upon pH-metry but 5/8 rats in which both procedures were performed had prolonged acid exposure. No esophagitis was seen. In conclusion, normal rats do not have reflux. Selective destruction of either the sphincter or the crural sling does not induce reflux, despite causing flattening of their respective manometric profiles. Conversely, combined inactivation of both components is significantly associated with reflux.