Acid Reflux Immediately Above the Squamocolumnar Junction and in the Distal Esophagus: Simultaneous pH Monitoring Using the Wireless Capsule pH System.

OBJECTIVES: The pattern of reflux in the most distal esophagus of asymptomatic individuals is largely unknown. Using a wireless technique we compared the degree and the pattern of acid reflux just above the squamocolumnar junction (SCJ) with that measured at the conventional level for pH monitoring. METHODS: Fifty-three asymptomatic volunteers underwent endoscopy with transoral placement of two pH recording capsules, one immediately above and one 6 cm above the SCJ. Ambulatory pH monitoring was performed during 48 h. RESULTS: Three subjects were excluded as the distal capsule was inadvertently placed with the pH electrode below the SCJ. The median percent time with pH < 4 and the median number of reflux episodes were significantly higher immediately above the SCJ compared with that found more proximally (16% vs 0.9% and 67 vs 26, p < 0.0001). Of all acid reflux events, 69% were isolated episodes immediately above the SCJ. Only 26% of reflux episodes detected at the SCJ extended to the more proximal pH electrode. Reflux events occurring just above the SCJ were more acidic. The number of reflux events with a minimum pH below 2 or 3 was significantly higher at the SCJ compared with that recorded by the upper capsule (1.6% and 44% vs 6% and 34%, p < 0.0001). CONCLUSIONS: Conventional pH monitoring substantially underestimates the degree of acid exposure in the most distal esophagus. In healthy subjects, acid exposure immediately above the SCJ was considerably higher and was characterized by shorter reflux episodes that had a lower minimum pH compared with that measured at the traditional level for pH monitoring