Focal Hypertrophy and Focal Spasm of the Pyloric Musculature in Adults #

In l952 Bachmann reported 12 cases with localized areas of hypertrophy of the pyloric musculature in adults. In each instance the hypertrophied area was situated on the lesser curvature; it was found as incidental pathology in a series of 600 autopsies and none of the cases had any other abnormalities of the stomach and duodenum. The cases were divided into three groups according to their relationship to the pyloric "sphincter". (Comment: the "sphincter" was equated with the pyloric ring). In the first group (5 cases) the thickening was situated directly in the "sphincter"; it resembled an enlarged version of the normal sphincter, consisting mainly of circular but also containing some irregular and longitudinal muscle fibres. In the second group (4 cases) the thickening was located a very short distance orally to the "sphincter", being separated from it by a narrow zone of normal tissues. In the third group (3 cases) it was situated in the "sphincter" as well as in the immediate prepyloric part. In the first two groups it appeared to be of a rounded or nodular character (while differing distinctly from a myoma), and in the third group it was rather longer than wide. In considering the pathogenesis, Bachmann asked himself whether these cases indicated that a certain part of the pyloric musculature was liable to undergo hypertrophy by virtue of its having a specialized function or structure.

Keet (l956) reported 2 adult operative cases in which the gastric resection specimens showed, as incidental pathology, a localized area of thickening of the pyloric musculature on the lesser curvature of the stomach. In the first case a true muscular hypertrophy was present; in the second the thickening appeared to be in the nature of a spasm, as it disappeared during the course of a few hours. We believe that the localized or focal pyloric muscular thickening in these two cases lends itself to a rational explanation on anatomical grounds, as indicated below.

Case Reports #

Case 25.1. G.V.L., 50 year old male, was admitted for partial gastrectomy because of a non-healing gastric ulcer, having had ulcer symptoms for the previous 12 years. Radiographic examination 6 years prior to admission had shown a tiny excrescence on the lesser curvature of the stomach 1.5 cm proximal to the pylorus, which was interpreted as a gastric ulcer. Three years prior to admission a second radiographic examination reported an ulcer niche on the lesser curvature, but failed to state its exact situation. Four months before admission a third radiographic examination showed a large gastric ulcer niche halfway up the lesser curvature in the region of the incisura angularis; there was no sign of the ulcer previously mentioned proximal to the pylorus. At operation the gall bladder was distended and contained calculi; there were no adhesions to the duodenum or pylorus. Palpation of the stomach in situ revealed a thickening of softish consistency in the pylorus on the lesser curvature side, diagnosed provisionally as a gastric polyp. A large gastric ulcer of the middle of the lesser curvature was seen and felt. Partial gastrectomy was done, the duodenum being divided 3.0 cm distal to the pyloric ring, well beyond the palpable thickening. A retrocolic gastrojejunal anastomosis was made and a cholecystectomy performed.

The macroscopic pathological examination of the resection specimen showed a large gastric ulcer on the lesser curvature 7.0 cm proximal to the pylorus. A mucosal fold, approximately l.0 cm high, separated the lumen of the stomach from that of the duodenum. In the pylorus, on the lesser curvature side and jutting into this mucosal fold, a rounded, pea-sized, rubbery hard mass was situated in the gastric wall. The mucosa, which was freely mobile on the underlying layers, was less mobile over the mass. There was no naked-eye evidence of ulceration locally. Microscopic examination showed the mass to consist of hyperplasia of the circular muscle (Fig. 25.1); it was not a myoma as it was not well defined and merged gradually into the surrounding circular muscle. The submucosa overlying the thickening was rather thin and contained numerous blood vessels. The pyloric mucosa and submucosa showed infiltration with inflammatory cells and changes of chronic gastritis. The ulcer on the middle of the lesser curvature proved to be a chronic, benign ulcer penetrating into the muscle layers.

Fig. 25.1. Case G.V.L. Microscopic section of pyloric nodule on lesser curvature side of pyloroduodenal junction, showing great hypertrophy of circular muscle fibres. Thin overlying submucosa

Case 25.2 M.B., 58 year old female, was admitted because of achylia gastrica. Radiographic examination showed an irregularity on the lesser curvature at the incusura angularis, which was regarded as a probable early gastric carcinoma. Partial gastrectomy was performed. The macroscopic examination of the fresh resection specimen showed a few hemorragic spots in its proximal part. At the pylorus, on the lesser curvature side, a hard pea-sized nodule was felt in the gastric wall. It was not particualrly well defined and was presumed to be a local thickening of the pyloric musculature. Microscopic examination showed well marked chronic gastritis with a few erosive defects in the mucosa and fibrotic tissue in the submucosa. When the specimen was handled again a few hours after it had been received, it was noted that the nodule previously felt at the pylorus on the lesser curvature side had disappeared. Except for the chronic gastritis no microscopical abnormalities were seen in the pylorus. 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. Aron et al. (l973) described the case of an elderly female in whom radiographic examination showed an hiatus hernia and a large filling defect on the lesser curvature side of the "distal antrum" with narrowing of the antral outlet. Endoscopy revealed oesophagitis while an irregular submucosal lesion measuring 2.5 cm x 0.5 cm was seen approximately l.0 to 2.0 cm proximal to the pylorus on the lesser curvature side; biopsy showed a normal mucosa. At operation a localized, firm, nodular mass measuring 3.0 cm in length and extending from the pylorus to the "distal antrum" on the lesser curvature, was found. Histology revealed marked hypertrophy of the circular musculature, diagnosed as torus hyperplasia which had presented as a gastric pseudotumor.

Liebermann-Meffert and Allgöwer (l977) investigated the morphology of the pylorus and "antrum" in gastric ulcer disease. In a series of 77 cases the ulcer was adjacent to the pylorus in 10, and in other parts of the stomach in 67. Focal areas of muscle hypertrophy which distorted either the "antrum", the pyloric ring or both were commonly found. The hypertrophy was not uniform but irregular, involving different parts of the pylorus and "antrum" to a variable degree. The findings were not described in detail nor interpreted in the light of the anatomy as determined by Cunningham (1906), Forssell (1913) and Torgersen (1942).

Discussion #

At least 27 cases of focal hypertrophy (including one of focal spasm) of the pyloric musculature in adults have been described in detail in the literature. Seventeen were not associated with other lesions in the upper gastrointestinal tract and apparently occurred de novo. Four cases were associated with chronic or atrophic gastritis (one also had achylia gastrica), one with an acute erosion, 2 with hiatus hernia, 2 with gastric and one with duodenal ulceration.

In 17 cases the hypertrophy (or spasm in one case) was limited to the pyloric muscle torus or knot. (The l7 cases in this group do not tally with the l7 mentioned above). Normally contraction of the pyloric muscle knot is a fleeting occurrence, being part of cyclical contraction of the sphincteric cylinder; it causes an evanescent widening of the lesser curvature part of the pyloric ring (Chap. 13). In focal hypertrophy of the muscle knot the mass occurs in the same situation and is permanent. The condition may be considered to be the pathological counterpart of a physiological stage of contraction.

Radiographically Seaman (l966) noted a permanent widening of the lesser curvature side of the pyloric ring in 2 of his 4 cases of torus hyperplasia. In retrospect this was also present in our Case 25.1. A similar but very advanced case was described by Aron et al. (l973). Torus hyperplasia should be considered in the radiological differential diagnosis of permanent widening of the lesser curvature side of the pyloric ring.

In 7 of the remaining l0 cases (described by Bachmann) the focal hypertrophy, while not strictly limited to the muscle torus, occurred in the same region and can probably be explained on the same basis. In 3 the hypertrophy occurred elsewhere in the pyloric musculature; this also applied to the cases of Liebermann-Meffert and Allgöwer (l977), which were not described individually.

It is concluded that focal hypertrophy is limited to the pyloric muscle torus in many instances, but this is not invariably the case and it may also occur elsewhere in the pyloric musculature. It may occur de novo or be associated with gastric ulceration (located more proximally in the stomach), chronic or erosive gastritis, hiatus hernia and duodenal ulceration. Whether it represents an early stage of diffuse adult hypertrophic pyloric stenosis is not known.

References #

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