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AccessibilityBarrett's Oesophagus
In Barrett’s oesophagus [Paull, 1976] the stratified squamous epithelium becomes replaced by columnar (gastric) epithelium for the 3 cm of the oesophagus above the lower oesophageal sphincter (LOS) (Figure 1).
FIGURE 1 – Barrett’s
oesophagus viewed
via endoscope
(click to enlarge)
The condition may be associated with an ulcer (Barrett’s ulcer) and has an abnormally high likelihood of undergoing malignant change, possibly 30–40 times that of normal oesophageal mucosa.
The principal aetiological factor in the development of Barrett’s oesophagus is reflux; in particular, more bile is found in the refluxate of these patients.[Richter, 1999] Conventional Barrett’s oesophagus is reported in 11–13% of patients with symptomatic reflux, and short segment Barrett’s oesophagus (<3 cm above the LOS) in 18%.[Navaratnam & Winslet, 1998] However, because columnar epithelium is more resistant to acid,[Johnson, 1987] Barrett’s oesophagus is associated with the alleviation of heartburn, and in one study 25% of patients known to have Barrett’s oesophagus had no symptoms of reflux.[Spechler, 1989]
Although bile is found more frequently in the oesophagus of patients with GORD, duodenal gastro-oesophageal reflux alone is not injurious to oesophageal mucosa but can result in significant mucosal damage when combined with acid reflux.[Vaezi & Richter, 1999] Mixed reflux (ie, from the stomach and from the duodenum) is more harmful than acid reflux alone, producing a possible toxic synergy.[Nehra, 1999] Cyclo-oxygenase (COX)-2, an enzyme involved in chronic inflammation and epithelial cell growth, may play a role in the development of Barrett’s oesophagus and subsequent malignant change. In vitro studies have shown that constitutive expression of COX-2 in normal oesophageal mucosa increases significantly in Barrett’s oesophagus and oesophageal adenocarcinoma and that COX-2 expression can be regulated by exposure to acid or bile salts.[Shirvani, 2000]
