Mechanisms of acid, weakly acidic and gas reflux after anti-reflux surgery

Background: Whereas it is well documented that fundoplication reduces acid reflux, the effects of the procedure on non-acid and gas reflux and the mechanisms through which this is achieved have not been fully elucidated. Methods: In 14 patients, reflux was measured with impedance-pH monitoring during a postprandial 90 min stationary recording period before and 3 months after fundoplication. Concomitantly, the occurrence of transient lower oesophageal sphincter relaxations (TLOSRs) and morphology of the oesophagogastric junction were studied with high-resolution manometry. This was followed by 24 h ambulatory impedance-pH monitoring. Results: Before fundoplication, two separate high-pressure zones (hernia profile) were detected during 24.9% of total time, during which there was a large increase in reflux rate. After fundoplication, the hernia profile did not occur. Fundoplication decreased the number of TLOSRs (from 10.5 (SEM 1.2) to 4.5 (0.7), p < 0.01) and also the percentage of TLOSRs associated with acidic or weakly acidic reflux (from 72.7% to 4.1%, p < 0.01). Nadir pressure during TLOSRs increased after surgery (from 0 (0-0) to 1.0 (1-2) kPa, p < 0.05). In the ambulatory study, there was a large decrease in prevalence of both acid (-96%, from 47.0 (5.9) to 1.8 (0.5), p < 0.01) and weakly acidic reflux (-92%, from 25.0 (9.7) to 2.3 (0.9), p < 0.01). The decrease in gas reflux was less pronounced (-53%, from 24.2 (4.9) to 11.3 (3.0), p < 0.01). Conclusions: Fundoplication greatly reduces both acid and weakly acidic liquid reflux; gas reflux is reduced to a lesser extent. Three mechanisms play a role: (1) abolition of the double high-pressure zone profile (hiatal hernia); (2) reduced incidence of TLOSRs; and (3) decreased percentage of TLOSRs associated with reflux.