Acid Reflux at the Gastroesophageal Junction. Pathophysiological and Diagnostical Aspects

Sammanfattning: Gastroesophageal reflux disease (GERD) has a prevalence of 20% based on weekly symptoms of heartburn and regurgitation. As reflux symptoms are unspecific for GERD, an objective evaluation of the presence of the disease is often needed. Ambulatory pH monitoring is the most commonly used diagnostic method but it is limited by relatively poor sensitivity, especially in patients without esophagitis. The diagnostic accuracy of esophageal pH monitoring performed immediately above the squamocolumnar junction (SCJ) was compared with that of the conventional level in patients with symptoms of GERD and healthy volunteers. The degree of acid exposure at the SCJ is significantly underestimated by pH monitoring at the conventional level. Using a predefined specificity of 90%, the sensitivity of the pH test was significantly greater for pH monitoring performed immediately above the SCJ compared with that of pH monitoring at the traditional level. In patients without mucosal injury, the sensitivity improved significantly from 45% to 66% and was further improved with the combination of a positive SAP for the symptom of heartburn to 94%. The highly acidic “acid pocket” in the proximal stomach after a meal, suggested to be important in the pathophysiology of GERD was studied with a pH electrode positioned immediately above the SCJ. Distal postprandial reflux was characterized by short, rapidly cleared reflux events of a relatively low acidity and the lack of prolonged periods of postprandial acid exposure questions the hypothesis that the acid pocket extends into the most distal esophagus and its importance in the pathogenesis of GERD. As complications of GERD, such as esophagitis, metaplasia and adenocarcinoma most commonly occur in the area of the gastroesophageal junction (GEJ), the acid environment in this area is of particular interest for the pathophysiology of GERD. The pattern and degree of acid exposure was measured immediately above the SCJ and associations with the endoscopic appearance of the SCJ and the presence of specialized intestinal metaplasia (IM) was evaluated. The histologic finding of IM at a normal appearing SCJ was significantly associated with abnormal acid exposure and frequent reflux episodes, but not with Helicobacter Pylori infection. With increasing degree of irregularity of the SCJ, the frequency and duration of reflux episodes, the degree of distal esophageal acid exposure and the prevalence of abnormal acid exposure increased progressively and significantly, suggesting that the shape of the normal SCJ is even and that also minimal irregularities are a consequence of acid reflux, likely due to formation of small areas of metaplastic columnar mucosa.