Timing of pyloric closure in man. Studies with impedance electrodes.

The timing of pyloric closure was studied at upper alimentary endoscopy in 20 subjects without antroduodenal pathology. Antral and duodenal contractions were recorded with balloon catheters and pyloric closure detected as a fall in impedance measured across two pairs of silver wire electrodes mounted around the shaft of the duodenal catheter 0.5 cm proximal to the balloon. During 300 min of good quality recording, active pyloric closure was observed on 193 occasions and 69% of closures were associated with antral or duodenal contractions within 2 sec. In 55.5% of the 154 isolated duodenal contractions (no preceding antral contraction), the pylorus, which was closed before the contraction, remained closed; in 32% the pylorus, which was open, closed within 2 sec of the contraction, while in only 12.5% was the pylorus open throughout. These observations suggest that the pylorus is able to close in response to an isolated duodenal contraction and thus may act as a barrier to duodenogastric reflux when antroduodenal contractions are not linked.