Introduction

An intact esophagogastric junction (EGJ) barrier consists of the lower esophageal sphincter (LES) in the same anatomical plane as the crural diaphragm (CD). When there is separation between the planes of the LES and the CD, the morphology of the EGJ is disrupted, and a hiatus hernia is identified on high resolution manometry (HRM). The integrated relaxation pressure (IRP) is typically measured as the nadir residual pressure across the EGJ during swallow induced LES relaxation.

Aims & Methods

Our aim was to determine if measurement of the IRP across the LES, both LES and CD, and across the CD alone yields different values, and whether differences, if any, have clinical implications. All patients undergoing HRM during a 3-year period at a tertiary facility were eligible for inclusion; incomplete studies were excluded. Demographics and esophageal function testing results were extracted from patient records. EGJ morphological subtypes consisted of type 1 when LES and CD were superimposed; type 2 when LES-CD separation was <3 cm, and type 3 when separation was ≥3 cm. Standard analysis consisted of IRP measured across the entire EGJ in type 1 and 2 EGJ, and across LES in type 3 EGJ. IRP was calculated across LES and CD, separately as well as together in type 2 and type 3 EGJ. An IRP threshold of <15 mmHg defined normal EGJ relaxation. Categorical variables were compared using chi square, and continuous values using Mann Whitney U. Absolute IRP values, and proportions with outflow obstruction were compared between EGJ morphological subtypes, and between LES IRP and CD IRP when a hernia was identified.

Results

Data from 467 patients (median age 54.0 years, 68.7% female, median body mass index 30.5 kg/m²) were analyzed, of which 61.2% had type 1 EGJ, 28.7% had type 2 and 10.1% had type 3 (Table). Using standard methodology, the median IRP was similar in the three morphological subtypes. However, when a hernia was present, IRP across the EGJ was significantly higher than that across either LES or CD (p<0.001), and LES IRP was significantly different from CD IRP (p<0.001). In type 2 EGJ, median IRP across LES was lower across the LES compared to CD (p<0.001). The CD was not traversed in 23 of 47 type 3 EGJ; in the remainder, LES IRP was similar to CD IRP (p=0.784). Of 11 patients with IRP>15 mmHg within types 2 and 3 EGJ, only 3 patients had persistent IRP elevation when LES and CD were separately assessed. Median AET increased as separation between LES and CD increased; patients with elevated IRP had normal AET (0.9, IQR 0.2-6.2). After differential IRP measurement, abnormal IRP was most frequent with type 1 EGJ, and IRP elevation across CD alone was rarely encountered.

Conclusion

In the presence of a hiatus hernia, the IRP across LES and CD together is higher than IRP recorded separately across LES and CD. We speculate that this is because the IRP measurement tool might be picking up pressurization within the hiatus hernia when IRP is measured across both LES and CD. Differential assessment of IRP across LES and CD can reduce over-diagnosis of outflow obstruction.