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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
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:
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.
- 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.
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.
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