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Introduction
The severity of gastroesophageal reflux disease (GERD) has been shown to correlate with the Hill classification of the gastroesophageal valve (GEV). As GERD worsens and the GEV deteriorates, patients progress from upright to bipositional reflux. We hypothesized that there may be significant changes in the configuration and function of the GEV depending on patient position as an explanation for the earlier occurrence of upright GERD.
Methods
We prospectively enrolled 47 consecutive patients with reflux symptoms in an IRB-approved observational study. Patients with prior foregut surgery or hiatal hernias >4 cm were excluded. Manometry was performed in upright, right lateral decubitus, and left lateral decubitus positions. Endoscopy was started in left lateral semi-recumbent position, and patients were repositioned upright partway through the endoscopy. Photographs were obtained of the GEV for grading in each position. During 48-hour ambulatory pH testing, information was gathered on whether patients were upright or supine. Outcomes were analyzed by type of GERD: upright or bipositional, and also by patient position.
Results
There were 16 patients with upright and 31 with bipositional GERD. Age, BMI, atypical GERD symptoms, and respiratory symptoms were not significantly different between the groups except that patients with purely upright reflux were more likely to be female. Patients with bipositional reflux on pH testing were more likely to have a deformed gastroesophageal valve on endoscopy in either position (see Table). There were no significant manometric differences between the groups. On pH testing, patients with predominately upright reflux had less esophageal acid exposure by every measure (including number of patients with a positive DeMeester score) than patients with bipositional reflux (see Table).
Endoscopically, Hill grade and other measures of valve deformity worsened when patients moved from a semi-recumbent to an upright position. Manometrically, LES mean basal pressure, LES mean residual pressure, and UES mean basal pressure were higher in the upright position compared to either left lateral or right lateral position. LES length and hiatal hernia length did not change based on position. On pH testing, all patients had more acid exposure when upright than when supine (see Table).
Conclusion
Patients with primarily upright reflux on pH testing had a more normal reflux barrier than those with bipositional reflux, both endoscopically and on pH testing. Endoscopically, the GEV becomes deformed when patients are moved to the upright position and functionally there is more esophageal acid exposure when patients are upright. These findings suggest that positional changes in the GEV may be responsible for the earlier onset of upright reflux.

	Patients with upright reflux only (n=16)	Patients with bipositional reflux (n=31)	p
% Male	13%	55%	0.006
Age	57	50	0.18
BMI	31	30	0.76
% with atypical symptoms	63%	53%	0.76
% with respiratory symptoms	56%	47%	0.94
Abnormal GEJ shape on endoscopy	48%	57%	0.05
% with positive DeMeester score	56%	97%	0.001
Acid exposure upright	6%	14%	0.0004
Acid exposure supine	8%	2%	0.0003
	Upright (n=47)	Recumbent (n=47)	p
Hill Grade	2.9	2.4	0.002
Abnormal GEJ shape on endoscopy	64%	46%	0.0003
LES basal pressure (mmHg)	14.7	8.3	0.006
Acid exposure (% of time)	11%	6%	0.00007