I don't and honestly don't know much about it, but this is from the 17th International Symposium on Gastrointestinal Motility, 14-17 sept. 1999,Conference Centre "Oud Sint-Jan", Bruges, Belgium.It has some info on gerd and hiatal hernia."Esophagus At the last International symposium a motor event was described in the esophagus that correlates withnon-cardiac chest pain. This unique motor pattern, sustained esophageal contraction (SEC) had nowby the same group (Mittal et al. San Diego USA) been shown to be closely associated with heartburnsymptoms. Reflux of acid in the esophagus can cause heartburn or chest pain. However, themechanism of acid induced pain is not known and both of these symptoms can occur in the absenceof acid reflux. Prolonged pH recordings show a poor correlation between the drop in pH in theesophagus and heartburn. SEC is recorded by high-frequency intraluminal ultrasound imaging of theesophagus. In 12 patients with heartburn, a close association between SEC and symptom of heartburnwas observed. SEC may therefore be the motor event that causes heartburn sensation and couldexplain why later can occur in the absence of heartburn. Despite the logical rationale whereby delayed gastric emptying and prolonged intragastric retention offood can increase the rate of transient LES (TLESRs) and reflux, only a moderate correlation has beenpreviously described between proximal gastric retention and TLESRs in patients withgastroesophageal reflux disease (GERD). Investigators from Leuven (Sifrim et al. Belgium) tested thehypothesis that simultaneous measurement of reflux by both intraluminal impedance and ph monitoringas well as gastric emptying, would better characterize the relationship between gastric emptying,TLESRs and reflux. Esophageal manometry and ph was recorded 4 hours postprandially in healthysubjects and gastric emptying was measured by octanoic breath test. The impedance techinque wasable to identify both acid and/or non-acid liquid or gas reflux. A significant correlation was foundbetween gastric retention, the number of TLESRs and occurrence of predominantly liquid reflux (acidand non-acid). Impedance detected early postprandial acid and or non-acid liquid reflux whosefrequency corrlelated weakly but significantly with the degree of gastric retention. In contrast, acidreflux detected by the pH monitoring did not correlate with gastric retention, perhaps due to bufferingof acid in the early postprandial period. Thus, new techniques such as intraluminal impedance and high-frequency intraluminal ultrasoundimaging of the esophagus can better elucidate the normal physiology and the pathophysiology of the esophagus and help us understand the underlying mechanisms in health anddisease. The role of hiatal hernia in patients with GERD has been a matter of debate. In patients with heartburnand acid regurgitation, hiatal hernia size correlated significantly with 24 h GER episodes (Lenglinger etal. Austria). Hiatal hernia size together with LES pressure, but not the amplitude of contractileresponses to swallowing and oesophageal clearance time, are of major impact for the extent ofgastroesophageal reflux."