Esophagogastric junction distensibility assessed with an endoscopic functional luminal imaging probe (EndoFLIP)

Abstract

Background: Increased esophagogastric junction (EGJ) compliance is a key abnormality in GERD leading to increased volumes of reflux. To date, EGJ distensibility has been measured only with investigational barostat-based prototype devices.

Objectives: The aim of the study was to test the endoscopic functional luminal imaging probe (EndoFLIP), a new commercially available technology designed to measure intraluminal distensibility, by assessing the EGJ of GERD patients and controls.

Design: Prospective case-control series.

Setting: Tertiary referral center.

Subjects: Twenty GERD patients and 20 controls studied during a routine esophagogastroduodenoscopy.

Methods: The EndoFLIP was passed through the endoscopic instrumentation channel and positioned across the EGJ. The EndoFLIP uses impedance planimetry to measure 16 cross-sectional areas (CSA) along with the corresponding intrabag pressure within a 4.6-cm cylindrical segment of a fluid-filled bag.

Main outcome measurement: EGJ distensibility was assessed with 10- to 40-mL volume-controlled distentions.

Results: In both groups, the least distensible locus at the EGJ was usually at the hiatus. As a group, GERD patients exhibited two- to threefold increased EGJ distensibility compared with controls, particularly at 20- to 30-mL distention volumes, values quantitatively similar to previous measurements with barostat-based devices. The endoscopic estimation of EGJ distensibility, the flap valve grade, correlated poorly with EndoFLIP measurements.

Limitations: Heterogeneity of GERD patients.

Conclusions: Measurement of EGJ distensibility with EndoFLIP is feasible during clinical endoscopy. Stratifying GERD patients according to this physiological parameter may facilitate the identification of patient subgroups responsive or unresponsive to medical or surgical treatments.

Figure 1

The Endoscopic Functional Luminal Imaging Probe (EndoFLIP) System. Once the bag is filled with a conductive solution, 16 intraluminal cross-sectional areas (CSA) are measured within the central part of the bag by the impedance measuring electrodes, whereas the pressure transducers provide the corresponding intrabag pressure. The volume of conductive solution injected from the syringe to the bag is controlled via the touch screen on the recording unit. The screen displays the calculated CSAs as a cylinder of varying diameter in real time along with the corresponding intrabag pressure. There is also the option of a split-screen display, as demonstrated here, which can display a snapshot from previous distention simultaneously with the current acquisition. (Photograph courtesy of Crospon Ltd., Galway, Ireland.)

Figure 2

Examples of a set of volumetric EndoFLIP distentions in a control subject (top) and a GERD patient (bottom). Typically the hourglass shape of the EGJ narrowed at the hiatus (white arrow) in both groups. In each panel, EGJ distention is illustrated as a cylinder of varying diameter corresponding to the 16 CSAs measured by impedance planimetry within the EndoFLIP bag along with the corresponding intrabag pressures. These examples were selected to illustrate the greater EGJ distensibility in a GERD patient with consistently larger hiatal distention at 20- to 40-mL distention volumes coinciding with lower intrabag pressure.

Figure 3

EGJ distensibility in control subjects and GERD patients. The EndoFLIP bag distensile pressure (x-axis) and the hiatal CSA (y-axis) were measured with the EndoFLIP bag filled to 10 mL (squares), 20 mL (diamonds), 30 mL (circles) and 40 mL (triangles). Both control subjects (open symbols) and GERD patients (closed symbols) exhibited measurable EGJ distention, particularly with 20- and 30-mL EndoFLIP bag volumes. However, the intrabag pressures associated with EGJ distention were consistently 6 to 15 mm Hg less in the GERD patients compared with the control subjects (see also Table 3). Data shown as medians.

Figure 4

Esophagogastric junction distensibility index in control subjects (white boxes) and GERD patients (gray boxes). *P = .02 versus controls.

Figure 5

Endoscopic assessment of EGJ morphology versus functional EGJ assessment with EndoFLIP. The qualitative grading of EGJ patency (gastroesophageal flap valve grade19) was not related to either hiatal CSA measurement (A) or EGJ distensibility index (B) in the pooled data from control subjects and GERD patients at the distention volumes of 20 and 30 mL. Bold lines denote medians.