In regards to upper GI endoscopy, what is an irregular z-line?

Gastroesophagel jctn. This refers to the appearance of the tissue where the esophagus and stomach meet. The z-line is a zig-zag line where these 2 different type tissues meet. Occasionally it can be irregular and protrude more into the esophagus and not have the typical appearance. This is generally a benign condition but can occasionally represent mild barrett's esophagus, a precancerous change caused by reflux.