The Role of Transsphincteric Pressure and Proximal Gastric Volume in Acid Reflux Before and After Fundoplication
2005; Elsevier BV; Volume: 129; Issue: 6 Linguagem: Inglês
10.1053/j.gastro.2005.09.018
ISSN1528-0012
AutoresRobert C.H. Scheffer, Hein G. Gooszen, Geoff Hebbard, Melvin Samsom,
Tópico(s)Helicobacter pylori-related gastroenterology studies
ResumoBackground & Aims: This study was conducted to explore the role of proximal gastric volume and transsphincteric pressure on acid reflux during transient lower esophageal sphincter relaxation (TLESR) in patients with gastroesophageal reflux disease (GERD) both before and after laparoscopic fundoplication. Methods: Twenty GERD patients were studied before and after fundoplication along with 20 healthy controls. High-resolution manometry and pH recording was performed for 1 hour before and 2 hours following meal ingestion (500 mL/300 kcal). Three-dimensional ultrasonographic images of the stomach were acquired before and every 15 minutes after meal ingestion. Results: Postprandial proximal to total gastric volume distribution ratios were significantly larger in GERD patients before fundoplication (0.57 ± 0.01; P < .05) and smaller following fundoplication (0.37 ± 0.01; P < .001) compared with controls (0.46 ± 0.01). The percentage of TLESRs associated with acid reflux did not relate to proximal gastric volume in any subject group. The transsphincteric pressure profile was different for TLESRs with and without reflux in GERD patients as well as in healthy controls. The pressure gradient across the esophagogastric junction (EGJ) (ΔEGJp) was greater for TLESRs with acid reflux compared with TLESRs without acid reflux in both GERD patients (11.4 ± 0.8 vs 8.0 ± 0.5 mm Hg, respectively; P < .01) and controls (10.6 ± 0.7 vs 7.1 ± 0.8 mm Hg, respectively; P < .05). After fundoplication, ΔEGJp during TLESRs was 7.9 ± 0.9 mm Hg, and the transsphincteric pressure profile markedly changed. Conclusions: Although proximal gastric volume plays a key role in eliciting TLESRs, it is not related to the incidence of acid reflux during TLESRs. The transsphincteric pressure gradient is greater in TLESRs associated with acid gastroesophageal reflux. Background & Aims: This study was conducted to explore the role of proximal gastric volume and transsphincteric pressure on acid reflux during transient lower esophageal sphincter relaxation (TLESR) in patients with gastroesophageal reflux disease (GERD) both before and after laparoscopic fundoplication. Methods: Twenty GERD patients were studied before and after fundoplication along with 20 healthy controls. High-resolution manometry and pH recording was performed for 1 hour before and 2 hours following meal ingestion (500 mL/300 kcal). Three-dimensional ultrasonographic images of the stomach were acquired before and every 15 minutes after meal ingestion. Results: Postprandial proximal to total gastric volume distribution ratios were significantly larger in GERD patients before fundoplication (0.57 ± 0.01; P < .05) and smaller following fundoplication (0.37 ± 0.01; P < .001) compared with controls (0.46 ± 0.01). The percentage of TLESRs associated with acid reflux did not relate to proximal gastric volume in any subject group. The transsphincteric pressure profile was different for TLESRs with and without reflux in GERD patients as well as in healthy controls. The pressure gradient across the esophagogastric junction (EGJ) (ΔEGJp) was greater for TLESRs with acid reflux compared with TLESRs without acid reflux in both GERD patients (11.4 ± 0.8 vs 8.0 ± 0.5 mm Hg, respectively; P < .01) and controls (10.6 ± 0.7 vs 7.1 ± 0.8 mm Hg, respectively; P < .05). After fundoplication, ΔEGJp during TLESRs was 7.9 ± 0.9 mm Hg, and the transsphincteric pressure profile markedly changed. Conclusions: Although proximal gastric volume plays a key role in eliciting TLESRs, it is not related to the incidence of acid reflux during TLESRs. The transsphincteric pressure gradient is greater in TLESRs associated with acid gastroesophageal reflux. Gastroesophageal reflux disease (GERD) is characterized by an increased frequency of acid reflux.1DeMeester T.R. Johnson L.F. Joseph G.J. Toscano M.S. Hall A.W. Skinner D.B. Patterns of gastroesophageal reflux in health and disease.Ann Surg. 1976; 184: 459-470Crossref PubMed Scopus (666) Google Scholar, 2Dodds W.J. Dent J. Hogan W.J. Helm J.F. Hauser R. Patel G.K. Egide M.S. Mechanisms of gastroesophageal reflux in patients with reflux esophagitis.N Engl J Med. 1982; 307: 1547-1552Crossref PubMed Google Scholar, 3Johnson L.F. DeMeester T.R. Twenty-four-hour pH monitoring of the distal esophagus. A quantitative measure of gastroesophageal reflux.Am J Gastroenterol. 1974; 62: 325-332PubMed Google Scholar In both controls and patients with GERD, the majority of reflux events are associated with transient lower esophageal sphincter relaxations (TLESRs).4Dent J. Dodds W.J. Friedman R.H. Sekiguchi T. Hogan W.J. Arndorfer R.C. Petrie D.J. Mechanism of gastroesophageal reflux in recumbent asymptomatic human subjects.J Clin Invest. 1980; 65: 256-267Crossref PubMed Scopus (828) Google Scholar, 5Dent J. Holloway R.H. Toouli J. Dodds W.J. Mechanisms of lower oesophageal sphincter incompetence in patients with symptomatic gastrooesophageal reflux.Gut. 1988; 29: 1020-1028Crossref PubMed Scopus (572) Google Scholar, 6Dodds W.J. Dent J. Hogan W.J. Helm J.F. Hauser R. Patel G.K. Egide M.S. Mechanisms of gastroesophageal reflux in patients with reflux esophagitis.N Engl J Med. 1982; 307: 1547-1552Crossref PubMed Scopus (933) Google Scholar, 7Mittal R.K. McCallum R.W. Characteristics and frequency of transient relaxations of the lower esophageal sphincter in patients with reflux esophagitis.Gastroenterology. 1988; 95: 593-599Abstract Full Text PDF PubMed Scopus (289) Google Scholar, 8Schoeman M.N. Tippett M.D. Akkermans L.M. Dent J. Holloway R.H. Mechanisms of gastroesophageal reflux in ambulant healthy human subjects.Gastroenterology. 1995; 108: 83-91Abstract Full Text PDF PubMed Scopus (301) Google Scholar In GERD, TLESRs occur as frequently as in healthy controls but are more likely to be associated with acid reflux.8Schoeman M.N. Tippett M.D. Akkermans L.M. Dent J. Holloway R.H. Mechanisms of gastroesophageal reflux in ambulant healthy human subjects.Gastroenterology. 1995; 108: 83-91Abstract Full Text PDF PubMed Scopus (301) Google Scholar, 9Sifrim D. Holloway R. Silny J. Tack J. Lerut A. Janssens J. Composition of the postprandial refluxate in patients with gastroesophageal reflux disease.Am J Gastroenterol. 2001; 96: 647-655Crossref PubMed Google Scholar, 10Trudgill N.J. Riley S.A. Transient lower esophageal sphincter relaxations are no more frequent in patients with gastroesophageal reflux disease than in asymptomatic volunteers.Am J Gastroenterol. 2001; 96: 2569-2574Crossref PubMed Google Scholar After fundoplication, both the number and percentage of TLESRs associated with acid reflux are markedly reduced.11Ireland A.C. Holloway R.H. Toouli J. Dent J. Mechanisms underlying the antireflux action of fundoplication.Gut. 1993; 34: 303-308Crossref PubMed Scopus (171) Google Scholar, 12Scheffer R.C. Tatum R.P. Shi G. Akkermans L.M. Joehl R.J. Kahrilas P.J. Reduced tLESR elicitation in response to gastric distension in fundoplication patients.Am J Physiol Gastrointest Liver Physiol. 2003; 284: G815-G820PubMed Google Scholar TLESR, a vagally mediated reflex, is triggered by gastric distension, especially distension in the area of the gastric cardia.13Holloway R.H. Hongo M. Berger K. McCallum R.W. Gastric distention a mechanism for postprandial gastroesophageal reflux.Gastroenterology. 1985; 89: 779-784Abstract PubMed Google Scholar Animal data indicate that both tension and stretch mechanoreceptors are present in the stomach.14Andrews P.L. Grundy D. Scratcherd T. Vagal afferent discharge from mechanoreceptors in different regions of the ferret stomach.J Physiol. 1980; 298: 513-524Crossref PubMed Scopus (137) Google Scholar, 15Blackshaw L.A. Grundy D. Scratcherd T. Vagal afferent discharge from gastric mechanoreceptors during contraction and relaxation of the ferret corpus.J Auton Nerv Syst. 1987; 18: 19-24Abstract Full Text PDF PubMed Scopus (100) Google Scholar, 16Iggo A. Tension receptors in the stomach and the urinary bladder.J Physiol. 1955; 128: 593-607Crossref PubMed Scopus (357) Google Scholar, 17Paintal A.S. A method of locating the receptors of visceral afferent fibres.J Physiol. 1954; 124: 166-172PubMed Google Scholar In recent studies, isovolumetric and/or isobaric barostat data have clearly shown that proximal gastric volume, via stretch receptors, plays a pivotal role in triggering TLESRs.18Penagini R. Carmagnola S. Cantu P. Allocca M. Bianchi P.A. Mechanoreceptors of the proximal stomach role in triggering transient lower esophageal sphincter relaxation.Gastroenterology. 2004; 126: 49-56Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar, 19Scheffer R.C. Akkermans L.M. Bais J.E. Roelofs J.M. Smout A.J. Gooszen H.G. Elicitation of transient lower oesophageal sphincter relaxations in response to gastric distension and meal ingestion.Neurogastroenterol Motil. 2002; 14: 647-655Crossref PubMed Scopus (54) Google Scholar In GERD, augmented and/or prolonged fundic accommodation has been repeatedly reported, and fundoplication reduces meal-induced adaptive fundus relaxation.20Penagini R. Hebbard G. Horowitz M. Dent J. Bermingham H. Jones K. Holloway R.H. Motor function of the proximal stomach and visceral perception in gastro-oesophageal reflux disease.Gut. 1998; 42: 251-257Crossref PubMed Scopus (115) Google Scholar, 21Tefera S. Gilja O.H. Olafsdottir E. Hausken T. Hatlebakk J.G. Berstad A. Intragastric maldistribution of a liquid meal in patients with reflux oesophagitis assessed by 3 dimensional ultrasonography.Gut. 2002; 50: 153-158Crossref PubMed Scopus (66) Google Scholar, 22Vu M.K. Straathof J.W. Schaar P.J. Arndt J.W. Ringers J. Lamers C.B. Masclee A.A. Motor and sensory function of the proximal stomach in reflux disease and after laparoscopic Nissen fundoplication.Am J Gastroenterol. 1999; 94: 1481-1489Crossref PubMed Scopus (98) Google Scholar, 23Wijnhoven B.P. Salet G.A. Roelofs J.M. Smout A.J. Akkermans L.M. Gooszen H.G. Function of the proximal stomach after Nissen fundoplication.Br J Surg. 1998; 85: 267-271Crossref PubMed Scopus (59) Google Scholar Despite this, the exact relationship between gastric volume, TLESRs, and the frequency of acid reflux remains unclear. Because the barostat technique, which has been considered to be the gold standard to assess gastric volume, is known to affect gastric accommodation24Mundt M.W. Hausken T. Samsom M. Effect of intragastric barostat bag on proximal and distal gastric accommodation in response to liquid meal.Am J Physiol Gastrointest Liver Physiol. 2002; 283: G681-G686PubMed Google Scholar and emptying,25Ropert A. des Varannes S.B. Bizais Y. Roze C. Galmiche J.P. Simultaneous assessment of liquid emptying and proximal gastric tone in humans.Gastroenterology. 1993; 105: 667-674PubMed Google Scholar we combined noninvasive 3-dimensional (3D) ultrasonography with concurrent manometry/pH-metry to examine why only some TLESRs are accompanied with acid reflux. We hypothesized that the transsphincteric pressure profile during a TLESR would differ for TLESRs with and without acid reflux. Therefore, the aim of this study was to explore the role of the proximal stomach and the transsphincteric pressure profile in determining acid reflux during TLESRs and to examine the effect of fundoplication on these parameters. Twenty GERD patients (12 men, 8 women; median age, 50.0 [29–69] years) were studied, along with 20 normal subjects (10 men, 10 women; median age, 28.0 [18–53] years). Patients were studied on 2 occasions, before and 3 months after laparoscopic Nissen fundoplication. The presence of GERD was established by symptom evaluation, upper gastrointestinal (GI) endoscopy, and 24-hour pH monitoring and defined by the presence of ≥Los Angeles A esophagitis on recent endoscopy (18 of 20) and/or abnormal 24-hour ambulatory pH monitoring using a cutoff value of 6.0% total time with pH 95%) (20 of 20).26Weusten B.L. Roelofs J.M. Akkermans L.M. Berge-Henegouwen G.P. Smout A.J. The symptom-association probability an improved method for symptom analysis of 24-hour esophageal pH data.Gastroenterology. 1994; 107: 1741-1745Abstract PubMed Google Scholar Fourteen GERD patients (70%) had endoscopic evidence of an hiatal hernia. All GERD patients had refractory symptoms despite at least 40 mg omeprazole daily. At 3 months after fundoplication, symptom evaluation, upper GI endoscopy, and 24-hour pH monitoring were repeated. Administration of proton pump inhibitors and/or antacids was discontinued for at least 7 days before the study. The protocol was approved by the Medical Ethics Committee of the University Medical Center Utrecht, and written informed consent was obtained from all participants. Laparoscopic fundoplication was performed using a technique described previously.27Bais J.E. Bartelsman J.F. Bonjer H.J. Cuesta M.A. Go P.M. Klinkenberg-Knol E.C. van Lanschot J.J. Nadorp J.H. Smout A.J. van der Graaf Y. Gooszen H.G. The Netherlands Antireflux Surgery Study GroupLaparoscopic or conventional Nissen fundoplication for gastro-oesophageal reflux disease randomised clinical trial.Lancet. 2000; 355: 170-174Abstract Full Text Full Text PDF PubMed Scopus (257) Google Scholar In short, the proximal fundus was mobilized by coagulating and dividing the gastrocolic and gastrosplenic omentum, including division of the short gastric vessels. The right crus was approximated, and a floppy 360° fundoplication of 3.0–3.5 cm was constructed. Three nonresorbable stitches were used to secure the fundic wrap. The fundic wrap and diaphragm were identified with 1 and 2 hemoclips (<1 cm apart), respectively, to be visible on future x-rays. The clip identifying the fundic wrap was placed in the angle of His before constructing the fundic wrap and was therefore located in the wrap after fundoplication. Esophageal manometry was performed using a 16-lumen assembly (OD 4.2 mm, ID 0.4 mm) that incorporated an array of 11 closely spaced (1-cm intervals) side holes to monitor distal esophageal, esophagogastric junction [EGJ], and proximal stomach pressures. Side holes 4, 8, 13, and 15 cm above the EGJ array recorded esophageal body and pharyngeal pressures. One side hole 2 cm below the EGJ array recorded intragastric pressure. Each catheter lumen was perfused with degassed water at a rate of 0.15 mL/min using a pneumohydraulic perfusion pump (Arndorfer Medical Specialities, Greendale, WI), and pressures were recorded with external pressure transducers (DPT-100, Medisize, Hillegom, The Netherlands). Pressure data were digitized at a sampling frequency of 25 Hz and processed using Trace 1.2v software (G. Hebbard, Melbourne, Australia) installed on a computer and using a data acquisition card (PCI-6023E National Instruments Corporation, Austin, TX). Esophageal pH was measured with a glass electrode (model LOT 440, Ingold A.G., Urdorf, Switzerland) positioned 5 cm above the proximal margin of the EGJ. Manometry and pH data were stored in a digital data logger set at a sampling frequency of 12.5 Hz and processed using Trace 1.2v, which is capable of displaying conventional line plots as well as topographic contour plots.28Clouse R.E. Staiano A. Alrakawi A. Development of a topographic analysis system for manometric studies in the gastrointestinal tract.Gastrointest Endosc. 1998; 48: 395-401Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar The 3D-imaging system consisted of a commercially available ultrasound (US) scanner (Esaote-Pie Medical, Maastricht, The Netherlands) with a 3.5 MHz curved US probe and a tracking system (Esaote-Pie Medical). The tracking system consisted of a transmitter generating a spatially varying magnetic field and a small receiver, attached to the US probe, containing 3 orthogonal coils to sense the magnetic field strength.21Tefera S. Gilja O.H. Olafsdottir E. Hausken T. Hatlebakk J.G. Berstad A. Intragastric maldistribution of a liquid meal in patients with reflux oesophagitis assessed by 3 dimensional ultrasonography.Gut. 2002; 50: 153-158Crossref PubMed Scopus (66) Google Scholar Using the 3D-imaging system, the US probe with attached sensor was used to localize the left lateral and superior margins of the stomach and the pylorus. The depth of scanning was adjusted enabling a US scan of the stomach, superior mesenteric vein, aorta, left liver lobe, and diaphragm or top of the gastric fundus. A standardized US scanning pattern was used, starting at the left lateral subcostal margin and then moving distally to the pylorus with the US probe in a vertical position. During the scan, all participants suspended their breathing in inspiration. For each ultrasound scan, approximately 300–400 2D ultrasound images were stored with a scan typically taking 15–20 seconds to complete. The outer profile of the muscularis propria was outlined, and the area was calculated automatically using the built-in calliper and calculation program of the US scanner. Using the 3D ultrasonographic technique, excellent in vitro and in vivo accuracy in volume estimation21Tefera S. Gilja O.H. Olafsdottir E. Hausken T. Hatlebakk J.G. Berstad A. Intragastric maldistribution of a liquid meal in patients with reflux oesophagitis assessed by 3 dimensional ultrasonography.Gut. 2002; 50: 153-158Crossref PubMed Scopus (66) Google Scholar, 29Gilja O.H. Detmer P.R. Jong J.M. Leotta D.F. Li X.N. Beach K.W. Martin R. Strandness Jr, D.E. Intragastric distribution and gastric emptying assessed by three-dimensional ultrasonography.Gastroenterology. 1997; 113: 38-49Abstract Full Text PDF PubMed Scopus (119) Google Scholar, 30Scheffer R.C. Gooszen H.G. Wassenaar E.B. Samsom M. Relationship between partial gastric volumes and dyspeptic symptoms in fundoplication patients a 3D ultrasonographic study.Am J Gastroenterol. 2004; 99: 1902-1909Crossref PubMed Scopus (23) Google Scholar with low interobserver variability30Scheffer R.C. Gooszen H.G. Wassenaar E.B. Samsom M. Relationship between partial gastric volumes and dyspeptic symptoms in fundoplication patients a 3D ultrasonographic study.Am J Gastroenterol. 2004; 99: 1902-1909Crossref PubMed Scopus (23) Google Scholar has been shown. Following an overnight fast, participants were seated comfortably in an upright position. The manometry assembly was passed transnasally after calibration and referencing of the catheter in vertical position to atmospheric pressure. Next, the assembly was positioned so that the array of 11 side hole recording sites was straddling the EGJ with 3 to 4 recording sites located in the distal esophageal body, 4 to 6 recording sites within the esophagogastric high-pressure zone, and at least 2 sites measuring intragastric pressure. Next, the pH catheter was inserted and positioned 5 cm above the upper margin of the EGJ. Subjects were allowed to accommodate to the presence of the catheter for 15 minutes. Next, 10, 5-mL boluses of water were given. This was followed by a 1-hour baseline and a 2-hour postprandial recording. The test meal consisted of 200 mL lactose- and fiber-free milk drink, containing 3.3 g protein, 12.0 g carbohydrate, and 4.3 g fat, 300 kcal (Nutridrink, Nutricia, Zoetermeer, The Netherlands) mixed with 300 mL H2O. The meal was ingested over 3 minutes, and the end of this period was defined as time zero. The time during ingestion was excluded from analysis of reflux and pressure events. Ultrasonographic data were acquired while fasting and at 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes following meal ingestion. Occurrence of antral contractions was observed by 2D ultrasound before meal ingestion to evaluate for phase III of the gastric migrating motor complex (regular contractions with a frequency of 3/min). If a phase III pattern was observed, meal ingestion was postponed until phase I returned. Esophageal body and EGJ motility were evaluated using a combination of conventional high-resolution manometric measurements and topographic contour plot assessment, wherein concentric contour rings indicate increasing pressure amplitude.31Alrakawi A. Clouse R.E. The changing use of esophageal manometry in clinical practice.Am J Gastroenterol. 1998; 93: 2359-2362Crossref PubMed Scopus (34) Google Scholar, 32Clouse R.E. Staiano A. Alrakawi A. Haroian L. Application of topographical methods to clinical esophageal manometry.Am J Gastroenterol. 2000; 95: 2720-2730Crossref PubMed Google Scholar For visual simplicity, pressure levels were also colored according to a legend (see Figure 5). The EGJ was defined as the high-pressure zone separating the abdominal from the thoracic cavity. Concurrent manometric and pH recordings were analyzed to characterize TLESRs, esophageal common cavities (CCs), and acid reflux associated with TLESRs. TLESRs were defined according to published criteria.33Holloway R.H. Penagini R. Ireland A.C. Criteria for objective definition of transient lower esophageal sphincter relaxation.Am J Physiol. 1995; 268: G128-G133PubMed Google Scholar A CC was defined as an abrupt increase in intraesophageal pressure approximating intragastric pressure in at least 2 distal esophageal recording sites.34Wyman J.B. Dent J. Heddle R. Dodds W.J. Toouli J. Downton J. Control of belching by the lower oesophageal sphincter.Gut. 1990; 31: 639-646Crossref PubMed Scopus (211) Google Scholar The pressure gradient across the EGJ at 1 cm above and below the EGJ at the start of a CC associated with the start of a pH drop was measured. For postfundoplication patients, TLESRs were scored if the nadir EGJ pressure during EGJ relaxation was equal to or less than the residual relaxation pressure determined during repeated water swallows.11Ireland A.C. Holloway R.H. Toouli J. Dent J. Mechanisms underlying the antireflux action of fundoplication.Gut. 1993; 34: 303-308Crossref PubMed Scopus (171) Google Scholar All EGJ pressure data were referenced to intragastric pressure, calculated as the mean end expiratory pressures recorded by the intragastric side holes. The pressure profile across the EGJ during TLESRs was determined as follows: First, the upper and lower borders of the EGJ were identified. These were defined as the interval between the first and last contour line bordering the EGJ. Contour lines were displayed at 2-mm Hg intervals between −15 and 80 mm Hg, followed by 5- and 10-mm Hg contours as values increased. Recording points between these contours were defined as being within the EGJ. Second, end expiratory nadir EGJ pressure was determined. This was defined as the tenth centile of the data generated using a “virtual sleeve” positioned across the EGJ from the start of relaxation to the reconstitution of the lower esophageal sphincter. Finally, the transsphincteric pressure profile (= axial pressure profile across the EGJ) was measured. To account for differences in pressure profile related to timing of respiration, measurements were made at a consistent point in the respiratory cycle. This point was selected to be at maximal inspiration (transition to inspiration) immediately prior to the onset of a reflux event (defined as an acid reflux event or a CC, see below) if present, or, if no acid reflux event or CC was present, at the first inspiration at maximal relaxation during TLESR. Once this time point was identified, the EGJ pressure profile was constructed by taking averaged pressures referenced to atmospheric pressure over a 2-second interval (1 second before and 1 second after the timepoint) from all recording sites from 2 cm below the caudal border to 2 cm above the cranial border of the EGJ. Averaged pressure profiles for TLESRs with and without acid reflux per subject were constructed as well as an average profile for each group (see Figure 5, Figure 6). From these pressure profiles, the transsphincteric pressure gradient (ΔEGJp) during a TLESR was calculated as the mean gastric pressure minus the mean thoracic pressure. To evaluate the relative position of the diaphragm within the EGJ, the respiratory inversion point (RIP), defined as the location of the respiration-associated inversion of pressure peaks within the EGJ, was determined.35O’Sullivan G.C. DeMeester T.R. Joelsson B.E. Smith R.B. Blough R.R. Johnson L.F. Skinner D.B. Interaction of lower esophageal sphincter pressure and length of sphincter in the abdomen as determinants of gastroesophageal competence.Am J Surg. 1982; 143: 40-47Abstract Full Text PDF PubMed Scopus (122) Google Scholar An acid reflux event was defined as a period with pH <4 following a drop of at least 1 pH unit with a rate of fall ≥0.5 pH units/s for a minimum duration of 3 seconds or, if esophageal pH was already below 4, a further drop in pH of at least 1 pH unit sustained for at least 3 seconds. The end of an acid reflux event was defined by the return of esophageal pH to at least 80% of baseline for at least 5 seconds. The duration of each reflux event was defined as time with pH <4 per reflux event.36Van Herwaarden M.A. Samsom M. Smout A.J. Excess gastroesophageal reflux in patients with hiatus hernia is caused by mechanisms other than transient LES relaxations.Gastroenterology. 2000; 119: 1439-1446Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar For gastric volume estimation, software with rendering and volume estimation capability was used (Invivo, Medcom, Darmstadt, Germany). The 300–400 2D sagital US frames were processed to construct 3D images. In the sagital US scan planes of the inner layer of the stomach wall, corresponding to the interface between the outer profile of the gastric wall mucosa and the liquid meal, were outlined in an average of 20–30 scans. The computer then generated gastric contours in the intermediate frames using a triangulation technique. A 3D reconstructed image was created from this data, and the volume of the proximal 10 cm of the stomach (cranial to a plane perpendicular to the longitudinal axis of the stomach as determined form the 3D image) was measured. The investigator was blinded to the order of the tracings in time and to the origin of the tracing (patient or healthy subject). To address the problem of air bubbles in the fundus, the visible amount of air was estimated according to Tefera et al21Tefera S. Gilja O.H. Olafsdottir E. Hausken T. Hatlebakk J.G. Berstad A. Intragastric maldistribution of a liquid meal in patients with reflux oesophagitis assessed by 3 dimensional ultrasonography.Gut. 2002; 50: 153-158Crossref PubMed Scopus (66) Google Scholar (0, no visible air; 1, small amounts; 2, moderate amounts; and 3, great amounts of air, disturbing the quality of the US, hence, necessitating exclusion from the study). Data were summarized as mean (SEM). Normality was tested using the Kolmogorov-Smirnov test. Averaged data for GERD patients before and after fundoplication were compared using a paired Student t test. Averaged 3D volume and EGJ pressure profiles data were compared among controls, GERD patients, and fundoplication patients using repeated measures analysis of variance (ANOVA). Pearson correlation test was used to determine correlations. For all statistical tests, the level of significance was set at P < .05. A total of 2 GERD patients (both grade 1), 3 healthy controls (1 grade 2; 2 grade 1), and 5 fundoplication patients (1 grade 3; 4 grade 2) had visible intragastric air pockets. None of the GERD patients or healthy controls but 3 of the Nissen fundoplication patients were excluded from analysis of proximal gastric volume: 1 because of large air pockets (grade 3) in the gastric fundus and 2 because of poor stomach visualization. Fasting total gastric volume was similar among the 3 subject groups: 35 ± 3 mL in the controls and 34 ± 3 mL before and 27 ± 3 mL after fundoplication. After the liquid meal, total gastric volumes were significantly smaller following fundoplication compared with before fundoplication (P < .001) and with controls (P < .001). Total gastric volumes did not differ between patients with GERD before fundoplication and controls (P > .05) (Figure 1). Assessment of proximal gastric volume showed a similar pattern, with fundoplication significantly reducing proximal intragastric volume (P < .001); however, GERD patients prior to fundoplication also exhibited larger proximal gastric volumes compared with controls (P < .001) (Figure 2). To account for these differences in total gastric volume, ratios were used to assess postprandial volume changes. During the first hour after the meal, proximal to total gastric volume distribution ratios were significantly larger before (P < .05) and smaller after (P < .001) fundoplication compared with healthy controls (Table 1).Figure 2Proximal gastric volume measurements in healthy subjects (○) and GERD patients before (♦) and after fundoplication (▵). Arrow indicates start of meal ingestion. *P < .001 GERD patients vs controls and #P < .001 fundoplication patients vs controls.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Table 1Postprandial Gastric Volume Distribution Ratios in Healthy Subjects and GERD Patients Before and After FundoplicationProximal/total gastric volume ratio 1st hour PPProximal/total gastric volume ratio 2nd hour PPControl subjects0.46 ± 0.0080.52 ± 0.010GERD patients0.57 ± 0.010aP < .05 vs controls., bP < .001 vs fundoplication.0.52 ± 0.015Fundoplication patients0.37 ± 0.012cP < .001 vs GERD patients and controls.0.46 ± 0.022NOTE. Values are means ± SEM. PP, postprandially.a P < .05 vs controls.b P < .001 vs fundoplication.c P < .001 vs GERD patients and controls. Open table in a new tab NOTE. Values are means ± SEM. PP, postprandially. The rate at whi
Referência(s)