PTU-138 Central Obesity and Waist Belt Cause Partial Hiatus Hernia and Short Segment Acid Reflux in Healthy Volunteers

Introduction Epidemiology demonstrates an association between obesity, hiatus hernia and acid reflux but mechanism is unclear. We have examined the structure and function of the gastro-oesophageal (GO) junction in healthy subjects with and without obesity and the effects of elevating intra-abdominal pressure with belt. Methods We recruited 8 subjects with normal ( < 94 cm males < 80 cm females) and 8 with increased ( > 102 cm males > 88 cm females) waist circumference, matched for age and gender. To allow accurate monitoring of location of the GO junction and its proximal movement during TLOSRs, a magnet (2x1 mm) was endoscopically clipped to the SCJ. Combined assembly of locator probe, high-resolution pH catheter and slimline manometer was passed nasally. After a standard meal, recording seated upright was continued for an hour. A waist belt was applied on a separate day throughout the entire recording. The effect of obesity was assessed by comparing obese vs. non-obese, both without belt. The effect of belt was assessed by comparing entire group with and without belt. The effect of belt in obesity was assessed by comparing belt-on vs. off in obese subjects. All results were in mean (SEM). Results Location of the SCJ (P = 0.006) and pH step-down (P = 0.01) were displaced proximally in obese vs. non-obese but the diaphragm was not displaced as reflected by peak LOS pressure (pLOS) and pressure inversion point (PIP) (Figure). With belt-on vs. off, there was similarly proximal displacement of SCJ and pH step-down and also of the diaphragm (P = 0.003) and LOS (upper and lower border, P = 0.01 and 0.03 respectively). In obese subjects with belt-on vs. off, there was proximal displacement of SCJ, pH step-down and diaphragm. There was marked proximal migration of SCJ during TLOSRs with its magnitude being less in obese vs. non-obese (4.2 vs. 6.8 cm, P = 0.04) and belt-on vs. off (3.9 vs. 5.5 cm, P = 0.01), consistent with its resting position being already proximally displaced. At traditional site (5 cm above LOS), the mean % time pH < 4 was minimal (0 – 0.5%) in all studied groups, however, acid exposure above the SCJ but below upper border LOS was increased in belt-on vs. off (6.2% vs. 1.6%, P = 0.01) and in obesity with belt-on vs. off (9.7% vs. 3.0%, P = 0.04) but not obese vs. non-obese (P = 0.2). Abstract PTU-138 Figure Conclusion Our findings indicate that in asymptomatic volunteers, central obesity and waist belt cause partial hiatus herniation and that