Distensibility of the esophagogastric junction assessed with the functional lumen imaging probe (FLIP™) in achalasia patients

Abstract

Background: The functional lumen imaging probe (FLIP), measures esophagogastric junction (EGJ) distensibility (cross-sectional area/luminal pressure) during volume-controlled distension. The aim of this study is to apply this tool to the assessment of the EGJ in untreated and treated achalasia patients and to compare EGJ distensibility with other diagnostic tools utilized in managing achalasia.

Methods: Findings from FLIP, high-resolution manometry (HRM), timed barium esophagram, and symptom assessment by Eckardt Score (ES) were compared in 54 achalasia patients (23 untreated, 31 treated). Twenty healthy volunteers underwent FLIP as a comparator group. The EGJ distensibility index (EGJ-DI) was defined at the 'waist' of the FLIP bag during volumetric distension, expressed in mm(2) mmHg(-1) . The ES was used to gauge treatment outcome: good response < 3 or poor response ≥ 3.

Key results: Of the 31 treated patients, 17 had good and 14 poor treatment response. The EGJ-DI was significantly different among groups, greatest in the control subjects and least in the untreated patients; patients with good treatment response had significantly greater EGJ-DI than untreated or patients with poor response. The correlations between EGJ-DI and ES and integrated relaxation pressure on HRM were significant.

Conclusions & inferences: The FLIP provided a useful measure of EGJ distensibility in achalasia patients that correlated with symptom severity. The measurement of EGJ distensibility was complementary to existing tests suggesting a potentially important role in the clinical management of achalasia.

Figure 1

Examples of the FLIP displayed EGJ geometry during a 40 ml distention in the three patient groups. EGJ distension is illustrated as a cylinder of varying diameter corresponding to the 16 cross-sectional areas (CSAs) measured by impedance planimetry within the FLIP bag. The corresponding intra-bag pressure is measured with a solid-state transducer also within the bag. Typically, the EGJ narrowed at the hiatus forming an hourglass shape with the locus of maximal constriction being the measurement of interest. The ‘waist’ at the EGJ in these examples is larger in the treated patient with a good response. Additionally, the pressure associated with the larger opening diameter is also lower, consistent with increased distensibility in this patient compared to the no-treatment and poor responder patients.

Figure 2

Comparison of the EGJ-DI during volume controlled distention in the four study groups. The overall EGJ-DI, defined as the CSA (mm²) divided by the intrabag pressure (mmHg), was greater in control subjects compared to untreated patients and poor responders. The good responders also had greater distensibility compared to poor responders and untreated patients, comparable to control subjects.

Figure 3

The correlation between EGJ distensibility index at 40 mL (EGJ-DI) and Eckardt score in treated patients (A). There was a moderate to weak inverse correlation between the two variables with ES rising as EGJ-DI decreased. The correlation between EGJ-DI and IRP in all patients (B). There was an inverse correlation between EGJ-DI and IRP.

Figure 4

The relationship between IRP, EGJ-DI, and bolus retention on timed barium esophagram, and ES in the group of treated patients. The EGJ-DI at 40 ml, and IRP are plotted on the axes and the data point for each individual is further characterized based on the ES and barium column height at 5 minutes (BC). There was a logical concordance between IRP and EGJ-DI at 40 ml in that there was no instance where the two were contradictory; there were no instances in which the IRP was abnormal and the EGJ-DI at 40 ml was normal (dark gray box). However, there were instances in which the IRP was normal and patients continued to have either bolus retention and/or an ES ≥ 3. The cut-off value based on the 95^th percentile for EGJ-DI at 40 ml (2.8 mm²/mmHg) had good discrimination for symptoms. Patients with an EGJ-DI at 40 ml > 2.8 mm²/mmHg and abnormal bolus retention had poor bolus clearance that was not directly related to an obstruction at the EGJ. Reduced emptying in this scenario was associated with low esophageal pressure that may be related to some esophageal dilatation and poor longitudinal muscle function. These defects would prevent the esophagus from pressurizing to a degree that facilitated bolus transit across the EGJ.