Mechanical properties of the relaxed EGJ

Heartburn and Acid Reflux Cure Program

Help for Acid Reflux

Get Instant Access

In contemplating the occurrence of reflux in the setting of a relaxed or hypotensive sphincter it is also necessary to consider other mechanical attributes of the system that may account for a relaxed sphincter remaining closed in one case and physically open in another; one such attribute is compliance, or distensibility of the sphincter. Acquired anatomic changes inclusive of, but not restricted to, hiatus hernia may alter the compliance at the relaxed EGJ thereby decreasing the resistance to gastroesophageal flow.

Recent physiologic studies exploring the role of compliance in GERD reported that GERD patients with and without hiatus hernia had increased compliance at the EGJ compared to normal subjects [50], [51]. These experiments utilized a combination of barostat-controlled distention, manometry, and fluo-roscopy to directly measure the compliance of the relaxed EGJ. Several parameters of EGJ compliance were shown to be increased in hiatus hernia patients with GERD: (1) the EGJ opened at lower distention pressure, (2) the relaxed EGJ opened at distention pressures that were at or near resting intra-gastric pressure, and (3) for a given distention pressure the EGJ opened about 0.5 cm wider (Fig. 8). These alterations of EGJ mechanics are likely secondary to a disrupted, distensible crural aperture and may contribute to the physiological aberrations associated with hiatus hernia and GERD.

Increased EGJ compliance may help explain why patients with hiatus hernia have a distinct mechanistic reflux profile compared to patients without hiatus hernia [52]. Anatomical alterations, such as hiatal hernia, dilatation of the diaphragmatic hiatus, and disruption of the gastroesopha-geal flap valve may alter the elastic characteristics of the hiatus such that this factor is no longer protective in preventing gastroesophageal reflux. In that setting, reflux no longer requires "two hits" because the extrinsic sphincteric mechanism is already disrupted. Thus, the only prerequisite for reflux becomes LES relaxation, be that in the setting of swallow-induced relaxation, tLESR, or a period of prolonged LES relaxation.

Increased compliance may also help explain why GERD patients may be more likely to sustain acid reflux in association with tLESRs compared to asymptomatic subjects. In an experiment that sought to quantify this difference, normal subjects exhibited acid reflux with 40-50% of tLESRs compared to 60-70% in patients with GERD [32]. This difference may be the result of increased EGJ compliance and its effect on trans-EGJ flow.

In the flow equation, flow is directly proportional to EGJ diameter to the 4th power and inversely proportional to the length of the narrowed segment and the viscosity of the gas or liquid traversing the segment. Should tLESRs occur in the context of an EGJ with increased compliance, wider opening diameters will occur under a given set of circumstances and trans-EGJ flow will increase. Patients without obvious hiatus hernia may still have increased compliance secondary to more subtle defects at the EGJ not readily evident using current radiographic or endoscopic methods of evaluation. These defects may be more akin to minor anatomical variants of the EGJ such as a grade-2 gastroesophageal flap valve or defects in the LES musculature.

Intrabag pressure relative to intragastric pressure (mmHg)

Fig. 8. EGJ cross sectional area as a function of distention pressure. Cross-sectional area at intrabag pressures > OmmHg was significantly increased in the NHH GERD patients compared to normal subjects (p < 0.0001) and in the HH patients compared top the NHH patients (p < 0.005). At pressures < 0 mmHg the EGJ cross-sectional area of HH GERD patients was significantly greater than both the NHH GERD patients and NLs (p < 0.05). At pressures below 0 mmHg there was no significant difference between NHH GERD patients and NLs (From [51]: Pandolfino etal (2003) Gastroenterology 125(4): 1018-1024, with permission)

Intrabag pressure relative to intragastric pressure (mmHg)

Fig. 8. EGJ cross sectional area as a function of distention pressure. Cross-sectional area at intrabag pressures > OmmHg was significantly increased in the NHH GERD patients compared to normal subjects (p < 0.0001) and in the HH patients compared top the NHH patients (p < 0.005). At pressures < 0 mmHg the EGJ cross-sectional area of HH GERD patients was significantly greater than both the NHH GERD patients and NLs (p < 0.05). At pressures below 0 mmHg there was no significant difference between NHH GERD patients and NLs (From [51]: Pandolfino etal (2003) Gastroenterology 125(4): 1018-1024, with permission)

Was this article helpful?

0 0
Herbal Remedies For Acid Reflux

Herbal Remedies For Acid Reflux

Gastroesophageal reflux disease is the medical term for what we know as acid reflux. Acid reflux occurs when the stomach releases its liquid back into the esophagus, causing inflammation and damage to the esophageal lining. The regurgitated acid most often consists of a few compoundsbr acid, bile, and pepsin.

Get My Free Ebook


Post a comment