Introduction

Surgery has proven to be the most effective treatment for obesity and its related comorbidities [1–6]. Laparoscopic adjustable gastric banding (LAGB) is one of the most commonly performed bariatric surgical procedures. It has advantages in terms of safety, adjustability, reversibility, and ease of insertion [7]. LAGB has been used for over 14 years internationally. In the USA, although the procedure has only been approved since 2001, a projected 100,000 procedures will be performed in the next 12 months, with this expected to rapidly increase in the future. LAGB patients require ongoing follow-up and management for life [8]. Symptoms such as reflux, regurgitation, or poor weight loss are likely to mandate investigation. It would be expected that during the follow-up years, many LAGB patients will develop symptoms that require physiological assessment. Currently, there is a lack of understanding of the normal physiology of the LAGB and the interpretation of investigations such as esophageal manometry remains unclear in these patients.

A LAGB is an adjustable silicone band that is placed laparoscopically around the cardia of the stomach. Secure placement 1–2 cm beneath the gastroesophageal junction appears critical to its success [9]. It is unknown exactly how the LAGB induces and sustains weight loss. While it is hypothesized to be a satiety inducing procedure [9], the exact mechanism of action has not been clearly defined. It is important to understand the physiological changes around the gastroesophageal junction induced by the LAGB. This will allow for better interpretation of investigations such as esophageal manometry.

There are limited and conflicting data concerning the impact of the LAGB on esophageal motility and the lower esophageal sphincter (LES). It has been suggested that the LAGB can induce esophageal motility disorders [10], with reports of significant esophageal dilatation [11]. Others have suggested no effect on esophageal motility or the LES [12, 13]. Impaired relaxation of the LES without an effect on tone [14, 15] has been a finding documented in two studies. Others have documented an augmentation in LES tone and length with [15] or without an impairment in esophageal motility [16]. The effect of altering the volume within the LAGB has not previously been studied. These confusing data and the lack of a “normal” standard to assess patients against have prevented manometry from being used in situations where it clearly has the potential to be invaluable.

Video manometry is a technique that combines high-resolution manometry with concurrent fluoroscopy. This allows for real time analysis and recording of physiological, anatomical, and transit data. A specifically designed computer program records and displays high-resolution manometry recordings as a color, spatiotemporal pressure plot alongside simultaneously recorded video images and allows for subsequent detailed analysis [17, 18].

This study was designed to define the high-resolution video manometric profile of the LAGB in patients with a successful outcome. We also aimed to analyze the effect of changing the volume of fluid within the LAGB on the LES, esophageal motility, the pressure profile around the gastroesophageal junction, and transit of liquids and semisolids through this region. It is hoped that improving the understanding of the physiology of the LAGB will allow the identification of a normal standard for video manometry, against which patients with poor weight loss or adverse symptoms can be evaluated.

Methods

This study was approved by the Melbourne Health Human Research ethics committee. Informed consent was obtained from participants.

LAGB patients whose surgery was considered to be successful, as defined below, volunteered to participate in the study after being given information during consultations with bariatric physicians. They were subsequently screened for suitability. Patients were recruited from a range of different time points following surgery (minimum 4 months). A control group of 20 patients prior to LAGB surgery was recruited.

Criteria for inclusion in the study (successful patients) include loss of >50% of excess weight (unless within 12 months of surgery), normal barium swallow within 12 months of enrolment in the study (performed as a part of routine care), absence of adverse symptoms such as reflux or vomiting, and confirmation that the volume of fluid within the LAGB was optimal by (a) absence of significant symptoms of reflux and (b) no requirement for change in the volume within the LAGB in the past 2 months. Exclusion criteria included current pregnancy, previous gastric surgery prior to LAGB placement, and age under 18 years or over 70 years.

A 21-channel water perfused manometry system with a custom made 21-channel silicone rubber manometry catheter (Dentsleeve, Ontario, Canada) was used to record pressures from the pharynx to the gastric body below the LAGB. The catheters were designed specifically to assess the region of the gastroesophageal junction and to differentiate the pressure signals generated by the LAGB from that produced by the LES. Side holes in the catheter were spaced 0.5 cm apart over a 9-cm high-resolution zone. Radiopaque markers were placed on the catheter to allow identification at fluoroscopy. The manometry system was connected to a personal computer via a data acquisition card and video input card (National Instruments). Simultaneous high-resolution manometry and video fluoroscopy information was recorded using TRACE! 1.2 (written by G Hebbard using LabVIEW, National Instruments, Austin, TX, USA).

All subjects underwent a standardized protocol:

  1. 1.

    Nasogastric intubation with manometry catheter

  2. 2.

    Identification of the LAGB (confirmation with image intensification if required)

  3. 3.

    Adjustment of the manometry catheter such that the most distal side hole was positioned 1 cm beneath the inferior aspect of the LAGB

  4. 4.

    Supine basal recording for 30 s (preceded by a 5-min accommodation period)

  5. 5.

    Ten wet swallows of 5 ml of water in the right lateral position

  6. 6.

    Esophageal video manometry see below (preceded by 5 min accommodation)

  7. 7.

    Rest for 10 min

  8. 8.

    Access the LAGB port with a 23-gauge noncoring needle attached to a three-way stopcock and syringe to allow repeated adjustment of the volume within the LAGB

  9. 9.

    Basal recordings altering the volume within the LAGB sequentially from an optimal level of restriction

  10. 10.

    Five further wet swallows with the band empty at 20% below optimal and 20% above optimal volume

Video manometry protocol:

  1. 1.

    Five-milliliter barium swallow anterior view—two swallows

  2. 2.

    Five-milliliter barium swallow lateral view—two swallows

  3. 3.

    One spoon of barium soaked porridge anterior view—two swallows

All pressures were referenced to end expiratory intragastric pressure, measured by the side hole placed distal to the LAGB. The catheter was placed such that the area of the LAGB and the LES were contained within the high-resolution zone.

Measurement of Lower Esophageal Sphincter Pressure

The LES basal pressure was recorded as the median peak end expiratory pressure over five consecutive respiratory cycles, following a minimum 15-s period in which no peristaltic activity was observed. The LES was differentiated from the LAGB (Fig. 2). If clarification of the position of the LES in relation to the LAGB was required, fluoroscopy was used to confirm the position of the structures by referencing the LAGB to radio-opaque markers on the manometry catheter. Alternatively, the LAGB port was accessed and fluid injected to identify a rise in pressure at the site of the LAGB (Fig. 1). A virtual sleeve was constructed by taking the highest pressure across the range of sensors designated as being within the sleeve zone.

Fig. 1
figure 1

a, b Changes in intraluminal pressure at the level of the LAGB during rapid injection of saline into the LAGB. Simultaneous display of focused color spatiotemporal plot (a) and virtual sleeve line (b) plot of pressure change at the level of the laparoscopic adjustable gastric band. These show a rapid rise and fall in pressure as saline is injected and reaspirated from the band. Scale shown on line plot is in millimeters of mercury. See Fig. 2 for color plot scale

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The LES pressure was measured with the band at its optimal volume and then, again, emptied of all saline. At each volume the virtual sleeve was placed selectively over the LES region. This incorporated the area of lower esophagus up to the upper part of the stomach above the band. An additional measurement was taken with the virtual sleeve placed over the entire region determined to represent the LES and Band complex.

LES relaxation was defined as the nadir pressure recorded in the region of the LES following pharyngeal initiation of swallowing until the LES reformed. The median relaxation over three to five swallows was used for analysis.

The length of the LES was measured as the contiguous length of the LES high-pressure zone (HPZ) greater than 5 mm Hg at end expiration. The basal intraluminal pressure at the level of the band was measured by locating the sleeve at the level of the band and recording the median end expiratory pressure over five respiratory cycles.

Esophageal Motility

Esophageal body motility was analyzed on the results of ten right lateral swallows of 5 ml of water. Each swallow and the overall motility pattern for each individual were classified based on published guidelines [19]. Each swallow was additionally categorized as normal or abnormal. An assessment was made of the presence of repetitive esophageal contractions following each swallow. Any pressurization in the esophageal body of 30 mm Hg or greater, initiated within 10 s of the esophageal contraction wave reaching the level of the lower esophageal sphincter, was classified as repetitive. This included situations when the patient swallowed again. This measurement was designed to identify the requirement for repeat esophageal contractions or pressurizations to propel a liquid bolus through the resistance produced by the LAGB.

Pressure Profile in the Region of the Gastroesophageal Junction

For each normal or hypertensive swallow at each of the volumes within the LAGB, a further detailed analysis was undertaken. Fig. 3 illustrates the parameters analyzed. The following data were collected: peak distal esophageal pressure, peak intraluminal pressure at the level of the LAGB, peak pressure at the level of the lower esophageal sphincter, length of the high-pressure zone (defined as the contiguous area of pressure greater than 5 mm Hg between the lower esophagus and the LAGB), and peak pouch pressure. Pouch pressure was defined as the peak pressure generated in the middle of the high-pressure zone (representative of the isobaric region of stomach between the lower esophageal sphincter and the LAGB).

The velocity of contraction was defined as the rate of movement of the 30 mm Hg isobaric pressure wave, over the lower 4 cm of the esophagus, between side holes. The location of the lower esophageal sphincter and the LAGB was taken into account to ensure that the velocity of the esophageal contraction was measured only over the lower 4 cm of esophagus.

Proportions were used for analysis. For each individual with three acceptable measurements, the median result for each parameter was recorded and used for pooled analysis.

Esophageal and Pouch Bolus Transit

Clearance of the bolus from the pouch and esophagus was measured during video manometry. Timing commenced from when the pharyngeal swallow was observed on manometry. The time taken for the bolus to pass completely from the gastroesophageal region above the LAGB into the stomach below the LAGB was recorded. Continuous fluoroscopy was used for a period of up to 1 min or until the bolus had passed into the gastric body below the band. If the bolus had not passed through the LAGB after 1 min, repeated screening was used at 30-s intervals until the bolus had moved into the stomach below the LAGB.

Statistical Analysis

Comparative values for continuous variables were analyzed using students t tests or paired t tests when measurements were taken on the same individual under different conditions, specifically when data were recorded with the LAGB at different volumes. A two-sided p value of 0.05 was considered statistically significant. Values were reported as means and standard deviation unless otherwise stated. SPSS version 11 (SPSS Inc, Chicago, IL, USA) was used for statistical computations.

Results

Twenty successful LAGB patients (five males) and 20 obese controls (six males), recruited from preoperative LAGB patients, participated in the study. Patient details are displayed in Table 1. All bands were LAP-BANDS (Allergan, Irvine, CA, USA). Ten 10 cm, three VG, and seven APS bands were used. The longest duration since surgery for the APS bands was 18 months as these have only been in use by our group since 2006. All patients tolerated the procedure well and were compliant with the study protocol.

Table 1 Patient weight and demographic details
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Fig. 1 shows a focused high-resolution manometry tracing from the region of the gastroesophageal junction codisplayed as spatiotemporal and virtual sleeve plots of pressure at this level. This demonstrates the rise and fall in pressure at the level of the LAGB produced by rapid injection and aspiration of fluid from the LAGB. When fluid is removed from the LAGB, this pressure signature disappears. Fig. 2 is a basal high-resolution manometry recording of a LAGB patient with the LAGB at its optimal volume. This shows that the LAGB produces an intraluminal pressure that is separate to and located below the lower esophageal sphincter.

Fig. 2
figure 2

A basal high-resolution manometry recording of a successful LAGB patient. The distinct pressure signatures produced by the LAGB and the LES can be clearly differentiated and their anatomical separation appreciated. The legend for interpretation of the color plot is shown at the right of the figure

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The mean basal intraluminal pressure at the level of the LAGB was 26.9 (19.8) mm Hg with the optimal volume in the band. There were only four patients in whom this pressure was greater than 30 mm Hg and only one patient with a pressure less than 10 mm Hg. Changing the volume in the band and comparing this with the values obtained at the optimal volume, it was found that when empty, this pressure was 2.72 (3.17) mm Hg, p = 0.038; when reduced to 20% under optimal volume, the pressure was 15.00 (7.53) mm Hg, p = 0.003; and when the volume was 20% over optimal, the pressure was 68.00 (38.10) mm Hg, p < 0.000.

Lower Esophageal Sphincter

In LAGB patients, the LES was found to be significantly attenuated in terms of length and basal tone, although it relaxed normally. In LAGB patients, the mean LES pressure was 11.21 (6.92) mm Hg. Nine patients had a hypotensive LES (less than 10 mm Hg). Only two patients had an LES >15 mm Hg. Table 2 summarizes the LES data obtained using different methods at optimal volume and empty. With the band empty, identical measurements were obtained using the two methods; therefore, only one value is displayed. Data from preoperative patients are also shown.

Table 2 Lower esophageal sphincter measurements in LAGB and preoperative patient
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These data show that when using a selective sleeve placed across the LES with the band at its optimal volume, the same value is obtained as with the band empty. Although when the sleeve was placed across the entire LES/Band complex, an artificially elevated LES tone and length are reported in conjunction with impaired relaxation. The LES/Band complex reports LES tone and length as being not significantly different from preoperative patients; however, impaired relaxation was observed.

Pressure Profile in the Region of the Gastroesophageal Junction

During swallows, a common cavity (isobaric) high-pressure zone was noted to develop between the advancing peristaltic pressure wave and the LAGB. This was found to represent the pressure within the fluid contained in a high-pressure zone of stomach between the LAGB and the lower esophageal contraction. This area was defined as the “high-pressure zone”. Fig. 3 illustrates a liquid swallow in a LAGB patient and demonstrates this. The high-pressure zone consisted of three components: the lower esophageal sphincter, the isobaric zone representing the “pouch of stomach” above the LAGB, and the intraluminal pressure within the stomach at the level of the LAGB.

Fig. 3
figure 3

Liquid swallow in a LAGB patient with the optimal volume in the band. Relaxation of the LES is observed; however, the LAGB pressure signature remains intact. The esophageal peristaltic wave progresses normally, followed by which a high-pressure zone develops above the LAGB. This high-pressure zone consists of three zones: the lower esophageal contraction, the isobaric region above the LAGB representing the gastric pouch, and the intraluminal pressure at the level of the LAGB

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At optimal volume, the mean length of the high-pressure zone was 4.07 (1.19) cm and in all patients, it was less than 6 cm in length. In all patients, this zone could be identified with the LES being a minimum of 2 cm above the band. This compared to the high-pressure zone in preoperative patients, i.e., the zone of high pressure induced by contraction of the lower esophagus of 2.86 (0.73) cm. Altering the volume within the LAGB produced significant changes in the length of this zone. Reducing the volume by 20% resulted in a significant decrease in the length of the high-pressure zone (p = 0.006) to 4.22 (1.02) cm. Similarly, emptying the LAGB of all fluid resulted in a significantly decreased (p < 0.001) length of this zone to 3.25 (0.88) cm. Increasing the volume by 20% significantly (p = 0.001) increased the length of the high-pressure zone to 6.05 (1.09) cm.

The velocity of esophageal peristalsis was found to be more rapid in the preoperative patients (3.14 (1.31) cm/s) compared to patients with the optimal volume in the LAGB (1.78 (0.78) cm/s, p = 0.001). Increasing the volume in the LAGB by 20% did not significantly affect the velocity of esophageal peristalsis (1.92 (0.9) cm/s, p = 0.616). When the volume in the LAGB was reduced by 20% (2.45 (1.44) cm/s, p = 0.056) or emptied of all fluid (2.58 (1.72) cm/s, p = 0.070), the velocity was not significantly changed.

Fig. 4 summarizes the data on altering the volume in the LAGB on the pressure profile in the distal esophagus and the region of the LAGB with different volumes in the LAGB. Lower esophageal pressure did not change with altering the volume in the LAGB, or in comparison to preoperative patients. Increasing the volume to 20% above optimal resulted in significantly increased distal esophageal pressure. The pouch pressure was not significantly changed by reducing the volume by 20%, although emptying significantly reduced these pressures, and increasing the volume by 20% significantly increased these pressures. The intraluminal pressure at the level of the LAGB progressively and significantly increased as the volume was increased from empty, 20% under optimal, optimal, and 20% over the optimal volume.

Fig. 4
figure 4

Effect of LAGB volume on gastroesophageal junction pressure topography during water swallows. For each separate anatomical structure in the region of the gastroesophageal junction, pressure data during water swallows are displayed. Fig. 3 illustrates the separation of these anatomical components during a liquid swallow. Data are displayed comparing the pressure recorded at each of the four locations stratified by LAGB volume. Data from preoperative patients are shown as a baseline comparison. The pressures generated at the level of the lower esophageal sphincter were not affected by the volume in the LAGB. The pouch pressure and intraluminal pressure at the level of the LAGB increased with addition of fluid to the band. Distal esophageal pressure increased significantly when the LAGB was overfilled. Error bars represent standard error of the mean. p values are in comparison to optimal LAGB volume. Significantly different values are represented by *p < 0.05 on the top of the column or **p < 0.005

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Esophageal Motility

In the preoperative patients, there were two patients with esophageal motility disorders. These were both mild esophageal peristaltic dysfunction. In the postoperative patients with the optimal volume within the LAGB, one patient fitted the criteria for an esophageal motility disorder that of hypertensive peristalsis, although this was asymptomatic.

Fig. 5 summarizes the results of the assessment of esophageal motility at different levels of restriction in comparison to the optimal volume. At optimal volume, 20% under, and empty, the LAGB patients had similar esophageal motility to the preoperative patients. There was no significant difference in terms of the number of abnormal swallows or when this was analyzed according to the subtypes of abnormal swallows. The only significant difference was the finding that the proportion of repetitive contractions (40%) was increased when the LAGB was at optimal volume, in comparison to the preoperative patients (16%), p = 0.024. Reducing the volume within the LAGB reduced the proportion of repetitive contractions although this did not reach statistical significance.

Fig. 5
figure 5

Effect of LAGB volume on esophageal motility. The proportion of swallows classified in each category according to high-resolution manometry criteria are shown stratified by LAGB volume. Data from preoperative patients are shown as a baseline comparison. More abnormal swallows and hypertensive swallows were observed when the volume in the LAGB was increased by 20%. Otherwise, no differences were observed between the preoperative patients and other LAGB volumes. Error bars represent standard error of the mean. p values are in comparison to optimal fill and are represented by *p < 0.05 on the top of the column or **p < 0.005

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Overfilling the LAGB by 20% resulted in a disruption of esophageal peristalsis. The proportion of normal swallows decreased to 50%. The majority of these were hypertensive contractions. The proportion of repetitive contractions also increased significantly to 58%, p = 0.024.

Transit in the Region of the LAGB

Esophageal transit during liquid (barium) swallows in the LAGB patients was 21 vs 8 s in the control group (p < 0.001). Transit of semisolids was 50 vs 16 s (p < 0.001). In only three of the LAGB patients were there retention of semisolid or liquid in the esophagus or gastric pouch above the LAGB for greater than 5 min. Compared to the control group, there was an increased duration of liquid and more prominently solid swallows. Transit of solids (porridge) took significantly longer in the LAGB patients than did the transit of barium (p < 0.001).

During swallowing, the response to pressurization of the pouch was flow across the LAGB and reflux into the esophagus of any remaining bolus once the esophageal contraction was completed. Reflux was followed by another primary or secondary esophageal contraction that resulted in bolus being pushed back into the pouch above the band and further flow being generated. Semisolids and liquids did not “sit” in the pouch above the LAGB.

Discussion

This study has used high-resolution video manometry to describe the physiological profile of LAGBs in patients with a successful outcome. In these patients, the presence of a LAGB has been shown to have consistent effects on the lower esophageal sphincter, esophageal contractility, and the transit of liquids and solids. Altering the volume of fluid within the LAGB also had predictable effects on the pressure profile of the distal esophagus and the region of the gastroesophageal junction at rest and during swallowing.

In this study, comparisons were made between successful patients, primarily acting as their own controls, with adjustments made to the volume of fluid in the LAGB. We chose to perform measurements at their “optimal” volume and compare these results with those obtained when the volume was varied to empty, 20% under optimal volume, and 20% over the optimal volume. These volumes were chosen based on our clinical observation that a change in volume of 20% has a clinically significant effect on weight loss and sensations reported by patients.

The LES was found to be significantly attenuated in LAGB patients in both tone and length, although relaxation was normal. This finding differs from previous reports of manometry in LAGB patients. Others have suggested that the LAGB has no effect on LES tone and enhances LES tone or that impaired LES relaxation is observed [14, 15]. Our results are likely to be more accurate due to the high-resolution video manometry technique used and our ability to clearly separate the LES and LAGB pressure signals. The finding of a deceased LES basal pressure is not surprising, as placing a high-pressure obstruction immediately beneath this can be expected to result in a degree of dilatation and likely attenuation of the LES. It is hypothesized that this attenuation of the basal LES pressure occurs progressively over time. Animal studies on the effect of placement of nonadjustable gastric bands, while not necessarily precisely reproducing the physiology of the LAGB, have documented similar effects on the LES to our findings [20].

At rest, the optimally adjusted LAGB produces a distinct intraluminal high-pressure signature just beneath the gastroesophageal junction, which is separate to the LES. This is of significance when performing manometry on a LAGB patient. If the LAGB is not accounted for, particularly if a sleeve sensor or a pull-back technique is used, the LAGB may be mistaken for the LES. Reporting the LES/Band complex pressure rather than the true LES will produce an erroneously elevated value for the LES, as well as inaccurate information on the relaxation and length of the LES. These findings account for the variable results obtained by others when assessing LES function and tone following LAGB.

The basal intraluminal pressure at the level of LAGB is likely to be an important measurement, as this is representative of the level of restriction produced by the LAGB. Without restriction, patients do not lose weight; alternatively, too much restriction results in adverse symptoms such as reflux. Sixteen of the 20 patients demonstrated a pressure between 10 and 30 mm Hg at their optimal volume. It may be that this represents the level of restriction that promotes weight loss without causing adverse symptoms or resulting in complications [21]. Varying the volume in the LAGB by amounts known to produce clinically significant effects resulted in measurable changes in the intraluminal pressure at the level of the LAGB. Emptying the band resulted in a near absence of a measurable intraluminal pressure, which correlates with patients reporting an absence of restriction and increased hunger [9]. Increasing the volume in the LAGB by only 20% above the optimal level resulted in a threefold increase in the pressure and disrupted esophageal function. Three patients had intraluminal pressures at the level of the LAGB greater than 40 mm Hg and up to 70 mm Hg at their optimal volume. Patients with a very “tight” LAGB, manifested by a high intraluminal pressure at the level of LAGB, may be at risk of developing the complication of symmetrical pouch dilatation [21]. It is assumed that the stretching of the stomach wall above the LAGB is as a result of chronic excessive pressurization of this region. This is likely to be due to a combination of poor eating behavior and an excessively tight LAGB [21].

During swallowing, an isobaric pressure zone consistently developed between the LAGB and the advancing pressure wave in the esophagus. This was the pressure within the gastric pouch above the LAGB. Once the peristaltic wave had reached the level of the lower esophageal sphincter, the high-pressure zone was measured. A measurement of the HPZ was defined (Fig. 3). It is important to note that this vertical length included the lower esophageal contraction, the isobaric zone representing the gastric pouch, and the intraluminal pressure at the level of the LAGB. The length of this zone remained less than 6 cm in all patients, with a median length of 4 cm and a minimum of 2 cm. The peak pressure generated in the pouch was found to progressively increase with the addition of fluid, as did the intraluminal pressure at the level of the LAGB. The peak distal esophageal pressure increased when the band was overfilled, most likely as a result of obstruction. This adds weight to the hypothesis that overpressurization of this region by overtightening the LAGB may contribute to complications following LAGB placement [21]. Our data illustrate the mechanisms by which this increased pressurization occurs.

Esophageal motility was found to be well preserved in LAGB patients with a successful outcome. Only one LAGB patient had a diagnosis of an esophageal motility disorder. In the control group, two patients were diagnosed with an esophageal motility disorder. Varying the volume between optimal, 20% under, and empty produced few changes in esophageal motility. A detailed analysis of the effect of altering the volume in the LAGB on esophageal motility identified two key effects. Repetitive esophageal contractions were observed in 40% of swallows in LAGB patients with the optimal volume in the LAGB, compared to only 16% of swallows in preoperative patients. Repetitive contractions appear to be of importance in the functioning of the LAGB as they appear to represent the response of the esophagus to a holdup in bolus transport across the LAGB, requiring a repeat esophageal contraction to generate flow across the LAGB. Increasing the volume in the LAGB to 20% over optimal induced a significantly increased proportion of abnormal swallows (50%): These were primarily hypertensive. Overtightening the LAGB also increased the proportion of repetitive contractions, as the esophagus tried to propel the liquid across the increased resistance of the LAGB.

Transit during liquid and semisolid swallows was relatively rapid in LAGB patients. During each swallow, there was a holdup of the liquid or semisolid bolus in the gastric pouch for a matter of additional seconds. This was more apparent during the semisolid swallows than the liquid. If the bolus did not completely pass through the LAGB prior to relaxation of the lower esophageal contraction, it was observed to actively reflux back into the esophagus and a repeat esophageal contraction was observed, repressurizing the area above the LAGB and generating further flow across the LAGB. These findings are suggestive of a consistent pattern of esophageal and pouch emptying in successful patients.

This study provides a reference point for clinicians investigating symptomatic LAGB patients using high-resolution manometry, with or without concurrent fluoroscopy. The importance of differentiating the LES from the band is emphasized. There was a consistent basal intraluminal pressure at the level of the LAGB representing the restriction produced by the band. An enlarged high-pressure zone (greater than 6 cm) or disruptions of esophageal peristalsis were not seen in a cohort of 20 successful LAGB patients. However, increasing the volume within the LAGB did significantly affect esophageal motility. In the majority of patients, transit of the food bolus was delayed only temporarily by the LAGB. Repetitive esophageal contractions appear to be a normal finding in LAGB patients with the optimal volume within the LAGB. These parameters can be assessed using high-resolution video manometry; however, they require an understanding of the expected anatomical and manometric profile in LAGB patients.

Our findings lead us to hypothesize that in successful LAGB patients, the food bolus impacts the gastric pouch due to ordered esophageal peristalsis, after which there is a slight, but noticeable delay, followed by pouch emptying. These events are associated with the generation of signals that mediate weight loss. Variations from this physiology may be an explanation for adverse symptoms or poor weight loss.