The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 25 (page 119)

Comments: Care should be taken with the interpretation of localized thickenings in gastric resection specimens, as these may be artifacts due to the application of clamps. This can be ruled out in the first case, since the thickening was felt with the stomach in situ and before clamps were applied. In the second case there was no obvious damage to the gastric wall at the site, such as one would expect after a clamp. The question may also arise whether the muscular thickening in the first case was not caused by healing of the old ulcer. Several points mitigate against this. The tiny excrescence originally interpreted as an ulcer niche was situated some distance orally to the pyloric aperture and not at the orifice, where the muscular thickening was subsequently felt. Second, the microscopic appearances were quite different from those of a healed gastric ulcer. Third, reference to the original radiographs raised serious doubt as to whether the excrescence was in fact an ulcer and not due to barium filling a furrow between mucosal folds.

The cases show, therefore, that there was focal thickening of the pyloric musculature, located in both cases on the lesser curvature at the pyloric aperture. In the first case the thickening was due to muscle hypertrophy, in the second to a temporary spasm. In both cases it was an incidental finding, and in both there was evidence of chronic gastritis, with an active gastric ulcer halfway up the lesser curvature in the first case.

From the above it will be clear that the focal muscular thickening in our 2 cases occurred in the exact situation of the pyloric muscle torus or muscle knot as described by Torgersen (l942). To the best of our knowledge these were the first cases to be reported in which it was shown that the anatomic basis for this entity derived from Torgersen's interpretation of the anatomy. Subsequently a number of authors based their findings in focal pyloric hypertrophy as well as in adult hypertrophic pyloric stenosis on the anatomy as determined by Cunningham (l906), Forssell (l913) and Torgersen (l942) (Chap. 3).

While Bachmann (1952) did not refer to Torgersen's findings, it is interesting to note that the hypertrophy in his first first group of cases occurred in exactly the same situation, and he in fact stated that the appearance resembled an enlarged version of a normal section of that region. Morphologically the cases described in Bachmann's second and third groups appear to be related to the first. Referring to the normal prepyloric contractions as described earlier (Chap. 13), it seems that the muscular hypertrophy in his second group occurred in the area where the peristaltic wave stops, i.e. a short distance orally to the pyloric aperture. The site and extent of muscular hypertrophy in his third group corresponds to the area of contraction on the lesser curvature normally occurring during a near maximal contraction of the pyloric sphincteric cylinder.

Skoryna et al. (l959), in their description of 6 cases of adult hypertrophic pyloric stenosis, included one case with moderate thickening of the entire pyloric "canal", with an additional small nodular mass on the lesser curvature side of the "canal" (i.e. at the muscle knot). Pathologically this proved to be a muscular nodule composed of circular fibres, diagnosed as focal hyperplasia of the muscle knot. There was no associated ulceration.

Mack (l959) described another case of focal hypertrophy of the muscle torus.

In 4 of the 7 cases of adult hypertrophic pyloric stenosis described by Knight (l96l), the hypertrophy was of a focal nature. In two of these it was localized to the muscle knot on the superior aspect (i.e. lesser curvature side) of the pyloric ring. In both the nodule was l.0 cm in diameter and consisted of circular muscle fibres. In the third case the hypertrophy was more extensive, involving the greater curvature and posterior wall, but not encircling the lumen, and extending proximally from the pyloric ring for a distance of 3.0 to 4.0 cm (i.e. the length of the sphincteric cylinder). In the fourth case a l.0 cm nodule of circular muscle fibres was found in the pylorus on the greater curvature side. None of these cases had associated gastric or duodenal ulceration, but chronic gastritis was present in two. Knight concluded that focal hypertrophy was not necessarily limited to the muscle knot, but that it could occur anywhere in the pyloric musculature. Whether it represented an early stage of diffuse hypertrophy was not known.

Heidenblut (l96l) described a case in whom a benign gastric ulcer was situated in the anterior gastric wall l.5 cm proximal to the pyloric ring. Directly opposite the ulcer in the posterior gastric wall a localized area of muscular thickening was found. It was thickest at the pylorus and extended for a short distance proximally into the "antrum", gradually thinning out. Microscopically it consisted of hypertrophied circular fibres. Changes of chronic gastritis were present in the mucosa and submucosa.

Wellman et al. (l964) described the autopsy findings in an elderly patient in whom an area of focal muscular hypertrophy occurred on the lesser curvature of the pyloric and immediate prepyloric region. The hypertrophy was confined to the circular musculature and was diagnosed as torus hyperplasia. A superficial erosion was seen in the overlying mucosa but no ulceration or ulcer scar was evident.

Seaman (l963, l966) described 4 adult cases of focal hypertrophy of the pyloric muscle in which the hypertrophy was limited to the muscle torus or knot. In all cases a firm, rounded, intramural mass was palpated at the lesser curvature aspect of the pyloric ring in the situation of the muscle knot. It varied in diameter in the different cases from 1.0 to 2.0 cm. In one case there was associated cholelithiasis and an hiatus hernia, in another a duodenal ulcer, and in a third associated atrophic gastritis; none was associated with a gastric ulcer. In all cases microscopic examination showed focal hypertrophy of the pyloric musculature. Of the 4 cases, one showed no definite radiographic abnormality. Two cases exhibited a widening of the space between the base of the duodenal bulb and the distal "antrum" on the lesser curvature side, i.e. a widening of the lesser curvature side of the pyloric ring. The fourth case showed a flattening of the distal lesser curvature of the "antrum" with a small protrusion which was not constant and not caused by an ulcer.

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