Objective: To determine the dynamic effects of a Nissen fundoplication on a volume-stressed lower esophageal sphincter (LES).
Design: Before and after experimental study in 10 baboons.
Setting: University animal research unit.
Interventions: Continuous manometric evaluation of the esophagus, cardia, and stomach during distention of the stomach with water. Slow motorized pull-through of the LES after each successive intragastric increment of 50 mL of water. Tests were performed again after a Nissen fundoplication.
Main outcome measures: Lower esophageal sphincter length and frequency of common cavity episodes after each volume increment. The pressure and intragastric volume at the yield point are defined as the point of permanent loss of the gastroesophageal pressure gradient.
Results: Gastric distention of the stomach with water resulted in a progressive decrease in LES length and competency. The median +/- interquartile range LES length decreased by 1.5 +/- 0.3 mm for every 1-mm Hg increase in gastric pressure before fundoplication and by 0.2 +/- 0.1 mm after fundoplication (P < .02). With gastric distention there was an indirect correlation between the degree of LES length and the frequency of reflux episodes (r = -0.70). This correlation was abolished by a Nissen fundoplication (r = -0.31). The median +/- interquartile range frequency of common cavity episodes (2.19 +/- 2.05 episodes per minute) before fundoplication decreased significantly (P < .001) to 0 +/- 0.59 episodes per minute after fundoplication. The median +/- interquartile range yield pressure (13 +/- 9 mm Hg) and yield volume (825 +/- 855 mL) were significantly (P < .01) improved after Nissen fundoplication to 39 +/- 36 mm Hg and 1250 +/- 750 mL, respectively.
Conclusion: By preventing sphincter shortening, a Nissen fundoplication improves competency of the LES to progressive degrees of gastric distention.