Chapter 17 (page 82)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 17 (page 82)

King et al. (l985) used real-time ultrasonic imaging to study the temporal relationships between contractions of the terminal antrum, pylorus and proximal duodenum in 22 normal subjects. The methodology was similar to that of their previous study (King et al. l984). A total of 259 cyclical periods of motor activity were observed during 32 recordings, a general pattern being seen in all.

Terminal antral contractions occurred in 98 percent of the cyclical periods of motor activity. The duration of the terminal antral contraction was relatively constant at about 4 seconds (mean 3.6 ± 0.6 sec) and pyloric closure occurred at the midpoint of these contractions. The pylorus then opened as the terminal antrum relaxed and remained open until the next TAC started. Pyloric closure occurred with each terminal antral contraction and was not seen at any other time. During the few (2 percent) cyclical periods of motor activity in which terminal antral contractions did not occur, the pyloric "channel" (presumably the pyloric aperture) remained widely patent. The observations provided no evidence of independent pyloric function, i.e. independent function of the pyloric ring, in the post-prandial state in humans. Sixty-seven percent of the TACs were associated with contraction of the duodenal bulb. Ninety-four percent of duodenal bulb contractions occurred about 1 second after pyloric closure. The remaining 6 percent were ectopic, i.e. apparently unco-ordinated with TACs. Duodenal bulb contractions lasted approximately 5 seconds.

Discussion

Real-time ultrasonic scanning plays an important role in the investigation of pyloric motility, pyloro-duodenal co-ordination and transpyloric fluid movement. Contractions of the pyloric region (designated pyloric "antrum" or "terminal antrum") closely resemble motility seen during radiological studies.

None of the authors quoted above related their findings to the specialized muscular anatomy of the pyloric sphincteric cylinder as described by Cunningham, Forssell and Torgersen (Chap. 3). However, it appears if the "terminal antrum" corresponds to the sphincteric cylinder. The finding that closure of the pyloric aperture occurs with each terminal antral contraction tallies with radiological observations that muscular closure of the aperture occurs during contraction of the sphincteric cylinder. According to ultrasonography the aperture closes as a gastric peristaltic wave reaches the midpoint of the terminal antrum, i.e. during terminal antral contraction (TAC). Radiologically it is seen that the aperture closes progressively during ongoing contraction of the cylinder. However, there is also an interplay between the right and left loops of the cylinder. If the left loop closes first, propulsion of contents into the duodenum occurs; if the right loop (surrounding the aperture) closes first, retropulsion from the cylinder (and not from the duodenum) into the more proximal part of the stomach occurs (Chap. 13). During maximal contraction of the cylinder both loops are tightly contracted and the aperture is closed.

In ultrasonography "forward flow" from stomach to duodenum, and "retrograde flow" from duodenum to stomach was described in association with TAC. The question arises whether true duodenogastric reflux was observed or whether retrograde movement of contents from the contracting sphincteric cylinder occurred.

With ultrasonography pyloro-duodenal co-ordination may be studied. This is hardly possible with conventional radiology; although it has been attemped by others, it has not been pursued in the present investigation. Ultrasonography has an advantage over radiology in that transpyloric flow of liquid contents may be quantified, using bran particles as sonic markers. Other advantages are that it is non-ionizing, non-invasive and non-traumatic.

Ultrasonography failed to identify independent action of the pyloric ring in the post- prandial state; this seems to confirm the view that the ring as such does not function as a sphincter.

References

Bateman DN, Leeman S, Metreweli C, et al. A non-invasive technique for gastric motility measurement. Brit J Rad l977, 50, 526-527.
Bolondi L, Bortolotti M, Santi V, et al. Measurement of gastric emptying time by real-time ultrasonography. Gastroenterology l985, 89, 752-759.
Holt S, McDicken WN, Anderson T, et al. Dynamic imaging of the stomach by real-time ultrasound: a method for the study of gastric motility. Gut l980, 21, 597-601.
King PM, Adam RD, Pryde A, et al. Relationships of human antroduodenal motility and transpyloric fluid movement: non-invasive observations with real- time ultrasound. Gut l984, 25, 1384-1391.
King PM, Heading RC, Pryde A. Co-ordinated motor activity of the human gastroduodenal region. Dig Dis Sci l985, 30, 219-224, 24.