Chapter 23 (page 104)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 23 (page 104)

Frimann-Dahl (l935) reported 3 cases and showed that muscular hypertrophy was not limited to the pyloric ring, as was commonly thought, but that it was up to 20.0 mm in length and involved the entire canalis egestorius. In his cases the musculature of the canalis was hypertrophied and strongly contracted, whereas the ring itself showed little thickening.

Runström (l939), in a study of 107 cases of IHPS, described the main patho- anatomical finding as a tumor as hard as cartilage, 2.0 to 3.0 cm in length and 1.5 cm thick, involving the muscular part of the stomach which had been designated the canalis egestorius by Forssell (l913); the muscular hypertrophy was not localized to the pyloric sphincter (i.e. the pyloric ring), but involved the entire canalis. Radiologically the contracted canalis presented as a tube with a narrow lumen 2.0 to 3.0 cm in length, completely lacking in "peristaltic motility". In contrast, the remainder of the stomach showed increased peristalsis, which invariably stopped at the oral end of the constriction. In addition a change occurred in the autoplastic movements of the mucosa, with mucosal folds filling the narrow passage in the contracted canalis; these factors resulted in a delay in gastric emptying.

Torgersen's (l942) microscopic sections showed that muscular hypertrophy in IHPS involved the two sphincteric loops together with the intervening fibres, i.e. the entire canalis egestorius. As the musculature of the remainder of the stomach was normal, he concluded that it was a pathological process limited to the canalis. Hypertrophy of the muscular wall with resultant narrowing of the lumen gave rise to the radiological picture of a permanently contracted pyloric canal. Torgersen (l942) agreed with Forssell (l913) that the radiological appearance of IHPS conformed to that seen in a maximal or near maximal contraction of the normal canalis. Contraction of the circular fibres of the muscularis externa produced narrowing of the lumen, and contraction of the longitudinal fibres produced shortening; the exact picture seen would depend on which of the two forms of contraction had gained supremacy.

Astley (l952) reiterated that in IHPS the prepyloric portion of the stomach was constantly narrowed and devoid of peristalsis. Radiologically this might present in a number of ways (Fig. 23.1). In some infants in whom no gastric emptying occurred for a considerable time, the distended stomach was seen to end in a small triangular projection or "antral beak". On either side of the beak a concave indentation occurred in the distal stomach due to the bulging pyloric musculature. Whem emptying did take place, the narrowed channel might present as a hair-line of barium, or as 2 or 3 parallel lines (crowded mucosal folds), or as a canal with a width of up to 3.0 mm. The canal was often slightly curved (concave upwards) and its length could vary between 8.0 and 30.0 mm. A concave indentation of the base of the duodenal bulb, again caused by the bulging pyloric muscle mass, might be present, resulting in a mushroom or umbrella-like appearance of the bulb. Incomplete filling of the stenotic area appeared as a gap between the "beak" and the cap.

According to Astley (l952) the following conditions could mimic the radiographic appearances of IHPS, and should be considered in the differential diagnosis:

A stage in the normal, cyclical contraction of the region. Referring to Forssell (l913), he mentioned that a maximal normal contraction of the canalis egestorius (Chap. 13) might simulate the contraction of IHPS. While the former is of a fleeting nature, the latter is permanent.
Infantile pylorospasm. In a series of 10 vomiting babies Astley (l952) noted that the normal process of widening of the prepyloric channel to its full calibre was considerably delayed in these cases. The narrowing persisted for 10 minutes to over an hour and simulated IHPS. However, continued observation showed that the segment was neither constantly narrowed nor devoid of peristalsis as it was in IHPS. After an interval gradual, or at times a more sudden relaxation occurred. The features were due to pylorospasm (Chap. 20) and were sometimes erroneously diagnosed as IHPS.
Gastric inactivity, i.e. failure of barium to leave the stomach due to absence of peristalsis. The retention could simulate that occurring in IHPS.

In a minority of cases of IHPS, the radiological findings were less easy to interpret; according to Astley (l952) these were cases in which filling of the stenotic area and duodenal bulb was of a fleeting nature, or in which free gastric emptying occurred.

Shopfner (l964) described an additional radiological sign of IHPS, namely the pyloric tit. This consisted of a sharp projection from the lesser curvature of the filled part of the stomach at the oral end of the constriction (Fig. 23.1). The tit was also seen in 2 cases of pylorospasm, and had exactly the same appearance as in IHPS, but disappeared when the spasm relaxed. The narrowing of pylorospasm resembled IHPS but disappeared within 5 to 10 minutes, enabling a differentiation to be made between the two conditions.

Not all the radiological signs occur in every case. In 14 proved cases of IHPS Haran et al (l966) noted the string sign in 11, the beak sign in 11, the tit sign in 6 and the shoulder sign in 5. These authors also described the doubletrack sign, consisting of 2 parallel linear streaks of barium with an interposed radiolucent band in the constricted channel. (Comment: The sign seems to be similar to one previously described by Astley in l952). While infantile pylorospasm might resemble IHPS radiologically, the "double-track" was not evident in their cases of spasm.

The radiographic features have been reviewed by Shuman et al. (l967), Haller and Cohen (l986) and others.

Swischuk et al. (l980, l989) pointed out that pylorospasm produced an "antral" deformity which was virtually indistinguishable from some forms of true IHPS. However, in spasm the configuration was less permanent, showing slight variations from time to time. The same authors described a number of cases of unusual, atypical or incomplete hypertrophy of the pyloric musculature, in which barium studies led to puzzling "antral" configurations, including funnel antrum, spiculated antrum, pyloric niche, and the lesser curve mass. The spiculated antrum was thought to be due to hypertrophied rings of circular muscularis externa, and the lesser curve mass to selective hypertrophy of the muscle torus (Chap. 25). With ultrasound and its ability to visualize the pyloric musculature directly, the diagnosis of IHPS in these cases left no room for doubt.