**2. Endoscopic detection of Barrett's oesophagus**

Barrett's oesophagus is most often identified incidentally in patients who are undergoing an upper endoscopy for investigation of reflux symptoms. Barrett's oesophagus has a classical endoscopic appearance of 'salmon pink' columnar mucosa arising proximally from the oesophago-gastric junction (OGJ), often with characteristic 'tongue' extensions. There may also be readily identifiable islands of columnar mucosa. Following endoscopic recognition, the extent of proximal extension above the OGJ should be measured and documented, taking care to accurately identify any sliding hiatus hernia which may confuse this measurement. The diagnosis must then be confirmed / corroborated histologically by multiple pinch biopsies of the affected segment. When biopsies are obtained it is crucial that they originate from the oesophagus and that their site is recorded as accurately as possible.

The 'Prague C and M criteria', defined by an International Working Group on Barrett's oesophagus, offers a validated method of classifying Barrett's based on its endoscopic appearance. (Sharma et al., 2006b) The extent of circumferential involvement in centimetres from the OGJ should be recorded, as should the maximum length of the Barrett's segment (including tongues of Barrett's but excluding isolated 'islands').

Difficulties arise in diagnosis particularly in 'ultra-short' segment Barrett's oesophagus. The original description of Barrett's oesophagus was of columnar metaplasia extending for at least 3cm from the OGJ. Although the risk of malignant progression is greater in long Barrett's segments (>8cm), it is now recognised that shorter lengths, even below 3cm have malignant potential. (Hirota et al., 1999; Schnell et al., 1992; Sharma et al., 1997; May et al., 2002) However, what appears endoscopically to be a short segment of Barrett's oesophagus in the distal oesophagus or an irregular z-line may in fact represent intestinal metaplasia of the gastric cardia known as cardia intestinal metaplasia (CIM). (BSG Working Party, 2005) This can lead to misclassification of CIM as short segment Barrett's. For this reason, the endoscopist has a crucial role in defining the exact position from which biopsies are taken to prevent misdiagnosis.
