Chapter 14 (page 69)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 14 (page 69)

Discussion

In the light of the anatomy as described by Cunningham (l906), Forssell (l913) and Torgersen (l942), and the radiological forms of movement as described by Torgersen (l942) and Keet (1957), the sequence of events as seen at gastroscopy, can probably be stated to be as follows: once the tip of the gastroscope is beyond the angulus but some distance proximally to the pylorus (with the gastric lumen distended by air), the pyloric aperture is visualized and seen to be open most of the time. At times ripples of contraction are seen, and at times annular contraction waves with a frequency of 3 per minute (peristaltic waves) move along the distal corpus and sinus to a well-defined ring, formed by the left pyloric loop. On the caudal side of the ring longitudinal mucosal folds may be seen to recede into the distance and end at the pyloric aperture (Fig. 14.1).

Fig. 14.1. Contraction ring formed by left pyloric loop. On caudal side of ring longitudinal mucosal folds recede into the distance, ending at pyloric aperture

The region of the stomach between the ring (the left pyloric loop) and the pyloric aperture is the pyloric sphincteric cylinder. The ring may narrow (Fig.14.2) and contract to a narrow bore, through which mucus or at times mucosal folds may be retropelled. This indicates the stage of maximal contraction of the sphincteric cylinder as seen radiologically (Chap. 13).

Fig. 14.2. Further narrowing of ring (left pyloric loop). The region beyond the ring and between it and the pyloric aperture (not visible) is the sphincteric cylinder

As the contraction causes the lumen to "disappear", the event itself (except for the contraction of the left loop) is not visible gastroscopically. In this sense maximal contraction of the pyloric sphincteric cylinder causes, gastroscopically speaking, an event horizon in the distal stomach. After a few seconds the sphincteric cylinder (including its left loop) relaxes, revealing the pyloric aperture, which is seen to be open (Fig. 14.3).

Fig. 14.3. Pyloric aperture distal to the ring

Should the tip of the gastroscope be closer to the pylorus, the pyloric aperture itself may be seen to close or open to a certain extent, in the absence of contraction of the sphincteric cylinder (marked air distension of the lumen may prevent contraction of the cylinder). In this case the variation in size of the aperture is thought to be due to iris-like action of the mucosal folds (Chap.13).