Chapter 14 (page 68)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 14 (page 68)

Blackwood (l969) pointed out that the correct interpretation of a ring structure in the pyloric region could present problems at gastroscopy, especially when it had an unusually large diameter, when a second ring was seen beyond it, or when radiology revealed a gastric lesion obviously distal to the ring structure visualized. In such cases it could be difficult to determine if one was dealing with the pyloric ring or with a different ring. In an attempt to improve the endoscopic evaluation of the pyloric region, he localized the pylorus by electrical potential difference (PD) measurements under direct gastroscopic vision. Of 9 studies, 7 revealed a significant PD change within 1.0 cm of the visualized ring, confirming the visual diagnosis of a normal pyloric ring. In all 7 cases the radiological appearance was normal. Two studies showed the PD change 3.0 to 4.0 cm beyond the visualized ring. In both, radiological abnormalities were evident in the stomach (one had an "antral" ulcer with narrowing, the other a "narrowed antrum"). These were regarded as cases of antral deformity mimicking the pylorus, i.e. false pyloric rings.

Comment: From the published radiographs of the 2 abnormal cases, it seems that the pyloric sphincteric cylinder was contracted in both. The "antral" ulcer in the first case was located within the cylinder. The rings visualized in these 2 cases must have been at the oral end of the contracted cylinder, i.e. in the situation of the left pyloric loop. The PD change 3.0 to 4.0 cm distal to the visualized rings confirms the above interpretation.

Of a total of l8 ring-like structures seen in the "distal antrum" at gastroscopy, Blackwood (l969) found 14 to be normal pyloric rings. Four of the l8 were "antral" deformities mimicking the true pyloric ring. It was concluded that about 4 out of 5 ring structures seen in the "distal antrum" would be pylorus, while about 1 out of 5 would be a different ring. The following criteria were suggested as aids in identifying rings in the distal antrum: the normal pylorus should be visualized distal to the occlusive portion of the "antral peristaltic wave" and remain patent and immobile between antral contractions. It should have the appearance of a sharply defined circumferential mucosal diaphragm projecting at nearly right angles to the antral wall. In cases of antral narrowing however, the wall would be observed to taper gradually to a narrowed area. An antral contraction wave might be seen to move smoothly in a caudal direction, distal to a ring-like structure. If mucosa distal to a ring was extruded proximally, it was likely that "antrum" was present distal to this particular ring. Blackwood (l969) finally defined the normal pylorus as a localized circumferential narrowing formed by a thin septum of mucosa with a small central aperture seen only, and remaining patent, between antral contractions, without mucosa or other landmarks being visualized distally.

According to Dagradi (l969), once the tipe of the gastroscope has been insinuated beyond the angulus, deep, rhythmic, sequential propagative waves of the "antrum" are commonly observed. These originate at the angulus, traverse the "antrum" and recede into the distance. On advancing the fiberoptic instrument, the waves are seen to terminate at a certain point of closure, where longitudinal mucosal folds are drawn together as if by a purse string. From this point a retrograde prolapse of bunched-up mucosa develops, somewhat resembling the opening of the petals of a flower bud; the point of closure has been likened to a rosette or "fleurette". Relaxation of the contraction ring follows, revealing the cavity of the "prepyloric antrum" and at its distal end the pyloric orifice. Normally the orifice is ring-like in configuration when seen head-on or oval if seen tangentially; at times it may be observed to contract or expand, changing slowly in diameter. Occasionally a false pyloric orifice may be seen which can be confusing. This usually occurs in association with a distal "antral" ulcer; the true nature of such a localized, unrelenting contraction ring becomes evident if the pyloric orifice can be observed distal to it.

Comment: The rosette-like point of closure again corresponds to contraction of the left pyloric loop, situated at the commencement of the pyloric sphincteric cylinder (Chap. 13). Retrograde prolapse or movement of mucosal folds during contraction of the cylinder is clearly visible radiographically (Chap. 13).

At endoscopy Kaye et al. (l976) found that the pylorus was frequently very narrow, but that it was usually not completely closed except during the terminal phase of an "antral" contraction.

Maratka (l984) mentioned that a congenital septum or an acquired fibrous septum (secondary to ulcer scarring) in the antral area might simulate the pylorus and could be called a "pseudopylorus".

Comment: The permanent "pseudopylorus" formed by a septum is obviously quite distinct from the normal intermittent, ring-like contractions of the left pyloric loop with its central aperture.

According to Varis (l989) endoscopy may fail to demonstrate motor disorders of the stomach, for instance in conditions such as diabetic gastroparesis.

Comment: One of the few shortcomings of endoscopy in the examination of the upper gastrointestinal tract is its inability to demonstrate the full range of gastric motor movements under physiological conditions. The very presence of an endoscope in the stomach with mechanical distension of the gastro-oesophageal junction, renders the examination unphysiological; so does air distension of the gastric lumen. Only movements ahead of the light source are seen and these cannot be correlated with those occurring more proximally.