Assessment of normal values of Esophagogastric Junction (EGJ) distensibility in healthy volunteers

The esophagogastric junction (EGJ) is a complex zone formed by the intrinsic
muscles of the distal esophagus (LES), the sling fibers of the proximal
stomach, the crural diaphragm and the phrenoesophageal ligaments. The EGJ is
responsible for maintaining a tightly closed antireflux barrier and a compliant
outlet to allow passage of food into the stomach after swallowing.
Until recently, the EGJ distensibility could be assessed using barostat and
hydrostat techniques, which have disadvantages and are clinically impractical.
Recently, an endoscopic functional luminal imaging probe (EndoFLIP) was created
which uses impedance planimetry to measure the geometry of a distensible organ.
The EndoFLIP device is a device suited to study the pathogenesis of esophageal
disorders as it provides measurement of the flow limiting diameter of the EGJ
under conditions in which it is challenged with volume distension. The EndoFLIP
system consists of a 240 cm long catheter with a 14 cm noncompliant bag on its
distal end which encloses 17 electrodes at 4 mm intervals. The probe is
connected to a mobile recording unit allowing real-time monitoring of the
measurements. At the end of upper gastrointestinal endoscopy, the catheter is
introduced transorally and the inflatable balloon is placed across the EGJ.
After proper placement of the balloon, the endoscope is withdrawn and the
balloon will be inflated to 20, 30, 40 and 50 ml distension volumes with a
specially formulated conductive solution. At each distension volume a 30 second
measurement will be performed and at the end of the measurements, the balloon
will be deflated and removed. Cross sectional areas (CSAs) are determined for
the 16 balloon cross sections during the volumetric distensions. Furthermore,
two pressure sensors are located on the probe to determine the intra-bag
pressure allowing assessment of the EGJ distensibility (narrowest CSA
mm2/intra-bag pressure mmHg). Measurements are monitored in real time to ensure
proper bag placement and each EndoFLIP measurement takes about 5 minutes.
Previous studies demonstrated that patients with GERD have a high EGJ
distensibility , whereas patients with achalasia have a low distensibility.
Furthermore, treatment of achalasia patients by pneumatic balloon dilation or
surgical myotomy leads to an increase in distensibility. Our research group
used the EndoFLIP device in GERD patients before and after endoluminal
fundoplication and we demonstrated that this treatment procedure leads to a
decrease in EGJ distensibility. Furthermore, patients with a low preoperative
EGJ distensibility have a better outcome compared to patients with a high
preoperative EGJ distensibility. However, we do not have normal values of EGJ
distensibility to compare the results from our previous GERD investigation.
Therefore, the aim of the present study is to assess the normal values of EGJ
distensibility in healthy volunteers.

Aim of the present study is to assess normal values of EGJ distensibility in
healthy volunteers.

The design conforms to a prospective, cohort study. Healthy volunteers will
undergo an upper gastrointestinal endoscopy and at the end of this procedure,
the EndoFLIP catheter will be introduced and the EndoFLIP balloon is placed
across the EGJ. The EndoFLIP balloon will be inflated with 20, 30, 40 and 50ml
distension volumes and at each distension volume a 30 second measurement is
performed during which CSAs, intra-bag pressure and EGJ distensibility are
assessed. At the end of the procedure, the EndoFLIP balloon is deflated and
removed.

Healthy volunteers will undergo an upper gastrointestinal endoscopy and
EndoFLIP measurement. The upper gastrointestinal endoscopy, performed by a
single experienced gastroenterologist, is a standard procedure that takes about
10 to 15 minutes. Diagnostic upper gastrointestinal endoscopy is a remarkably
safe procedure. One large US study estimated an overall complication rate of
0.13% (including mucosal biopsy) and an associated mortality of 0.004%. Very
few people experience side effects from gastroscopy. Patients may have a
slightly sore throat after the procedure. Air may also be trapped in the
stomach causing that subjects feel bloated, but this usually clears up quite
quickly. At the end of the upper gastrointestinal endoscopy, EGJ distensibility
will be assessed using the EndoFLIP system. The EndoFLIP system has been used
in different studies and no complications were described. Verlaan et al,
reported that two patients refused to undergo an EGJ distensibility measurement
after achalasia treatment because of discomfort experienced during the
measurement before the treatment procedure. Our research group used the
EndoFLIP system before in GERD patients without complications and the
measurement was well tolerated.
In case of unexpected findings during gastroscopy of healthy controls, these
will be reported to the subject and to his/her general practitioner.