The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 13 (page 55)

Do Gastric Peristaltic Waves Progress as far as the Pyloric Aperture?

In a consideration of motility patterns of the distal 3.0 to 4.0 cm of the stomach, it is necessary to determine if gastric peristaltic waves normally proceed as far as the pyloric aperture.

Golden (l937) stated that each narrow peristaltic wave proceeding down the stomach terminated in "antral systole", i.e. a segmental or concentric contraction of the entire canalis egestorius described by Forssell (l913), which corresponds to the pyloric sphincteric cylinder.

Other authors differed. During simultaneous cineradiographic and kymographic studies in man, Smith et al. (l957) found that both Type I and Type II waves invariably progressed over the antrum toward the pylorus in a peristaltic manner. In some cases the pylorus failed to relax as barium was driven towards it (which implied that the waves proceeded as far as the pylorus); in other cases the wave faded just proximal to the pylorus.

Rhodes et al. (l966) stated that propulsive contractions arose near the incisura angularis and progressed smoothly towards the pylorus (from which it is concluded that they reached the pylorus).

Carlson et al. (l966), during simultaneous cineradiograpic, pressure and electrical studies in dogs, found that Type I waves passed in a continuous, peristaltic manner to the pyloric ring. Type II waves behaved differently; when such a wave reached a point 3.0 to 4.0 cm from the pyloric ring, the terminal segment of the antrum and the pyloric canal contracted in a segmental, simultaneous way. The contraction, designated a terminal antral contraction (TAC), was followed by relaxation. An antral cycle was the time from completion of one antral contraction wave to completion of the next. The pyloric canal almost always contracted with the terminal antrum. (Comment: Pyloric canal was equated with the pyloric aperture). Sometimes the pyloric canal would narrow early in the cycle but not completely close, so that movement of the contents through it into the duodenum occurred while the "antrum" was contracting. Simultaneous contraction of the terminal antrum and pyloric canal had an important effect on luminal contents; when contraction occurred, most of the contents were forcefully regurgitated into the proximal antrum (retropulsion) instead of being propelled into the duodenum (propulsion). Thus Type II contractions had a dual action, viz. propulsion into the duodenum and retropulsion into the stomach. Each TAC correlated with a sharp increase in intraluminal pressure. The mean rate of TAC's was 4.8 per minute in dogs.

Carlson et al. (1966) found that over the proximal antrum a definite interval always occurred between the detection of basal electrical rhythm (BER) at successively distal electrodes. As the BER complex reached the terminal antrum, its rate of conduction increased several fold and it was detected simultaneously, or nearly simultaneously, at successive electrodes, providing the pattern for TAC. The pyloric canal was closed during TAC and the rest phase following on TAC; it was open during peristalsis before the onset of TAC.

Edwards and Rowlands (l968) described Type I waves as shallow, annular, moving constrictions that progressed along the body of the stomach towards the pylorus. Type II waves were a deeper version of the former. As these constrictions approached the distal 4.0 cm of the stomach, instead of continuing in a sequential manner to the pylorus, they ended in a simultaneous, concentric contraction of the entire 4.0 cm long segment.

According to Code and Carlson (l968) three patterns of peristaltic activity are to be observed in this region: (1) some peristaltic contractions diminish in amplitude as they progress into the terminal antrum, where they simply fade away; (2) some contractions pass with increasing vigour over the entire antrum to end abruptly at the pylorus; (3) most peristaltic contractions end with segmental, simultaneous contraction of the terminal antrum and pyloric canal, closing the pylorus. Cineradiography showed that TAC and the contraction that closed the pyloric canal started simultaneously, but the pyloric canal usually closed earlier in the sequence than the rest of the "antrum"; it remained closed throughout the continuation of the terminal antral contraction. Sometimes the pyloric canal narrowed early in the cycle, without closing completely, so that intraluminal contents moved through it into the duodenum while the antrum was contracting.

The maximum rhythmic frequency of TAC's corresponded to the rhythmic frequency of gastric peristaltic contractions, namely 4 to 5 per minute in dogs and 3 per minute in man. The frequency of Type I or Type II contractions corresponded to the frequency of the basic electrical rhythm (BER).


With the exception of Golden (l937) and Edwards and Rowlands (l968), the authors mentioned above did not base the concentric, segmental, simultaneous contraction of what they called the terminal antrum (TAC) on any unique characteristic or specialization of the musculature of the wall of this part of the stomach. Yet Forssell (l913), Cole (l928) and Torgersen (l942) had stated previously that the forms of movement in this region depended on the specialized muscular build which had been described by themselves as well as by Cunningham (l906) (Chap. 3). It comes as some surprise to note that in investigations of gastric motility in human subjects, the above anatomical findings have been almost universally ignored. Only Golden (l937) stated that as far as motility was concerned, the canalis egestorius of Forssell (l913) was the most important part of the stomach; unfortunately he equated the term "antrum" with "canalis egestorius". Forssell (1913) had been adamant that "antrum" had no basis in anatomical fact, whereas canalis egestorius was a well defined anatomical entity.

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