S874 Pilot Retrospective Study: Clinical Associations of Hiatal Hernia and Body Mass Index With Esophageal Reflux and Manometry Profiles

Introduction: Hiatal hernia is frequently implicated in the pathogenesis of gastroesophageal reflux disease (GERD), its relationship with reflux burden and esophageal motility parameters remains incompletely defined. Nocturnal GER has a significant impact on quality of life. The study aimed at evaluating the association of a hiatal hernia (HH) with nocturnal GER using high-resolution manometry (HRM) and 24-hour pH impedance testing (24 hr-pH). Methods: This was a single-center retrospective study that analyzed adult patient records (more than 18 years of age) who underwent 24 hr-pH and HRM testing. We included HH status, body mass index (BMI), HRM findings (lower esophageal sphincter [LES] basal pressure, integrated relaxation pressure [IRP], ineffective swallows), and 24 hr-pH parameters (Demeester score, total/upright/supine acid exposure time [AET], longest reflux episode, mean nocturnal baseline impedance [MNBI], weakly/non-acidic reflux). Analysis was performed in Stata; group comparisons were performed using Mann-Whitney U and Chi-square tests. Pearson correlations assessed associations between continuous variables, including BMI and manometric findings. Results: Although we noted the hiatal hernia group had a higher mean value for Demeester score, distal AET, upright AET, supine AET, and longest reflux episode there was no statistically significant difference to suggest more nocturnal GER (P > 0.18). BMI was positively correlated with supine AET (r = 0.33, P = 0.036) and longest reflux episode (r = 0.33, P = 0.039) and negatively correlated with MNBI (r = -0.45, P = 0.004). A subgroup analysis of HRM and pH correlation, revealed IRP showed consistent negative correlations with Demeester score (r = -0.44, P = 0.005), total AET (r = -0.45, P = 0.005), upright AET (r = -0.34, P = 0.035), supine AET (r = -0.44, P = 0.006), and longest reflux episode (r = -0.40, P = 0.016), while positively correlating with MNBI (r = 0.44, P = 0.007). Conclusion: Our preliminary findings suggest that higher BMI is associated with higher supine AET and long reflux episodes, but HH presence does not directly correlate with nocturnal reflux severity in this pilot cohort. The non-significance is attributable to the small sample size inherent to a pilot study, which limits statistical power. HRM parameters, especially IRP and LES basal pressure, show robust relationships with pH-impedance metrics, highlighting their pivotal diagnostic utility. Future directions include expanding the sample size and exploring the impact of proton pump inhibitor use on nocturnal reflux.