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Chapter 23 (page 110)
In considering the pathogenesis, it should be noted that many authors held the view that
the pyloric canal was elongated in IHPS (Shopfner l964; Shuman et al. l967; Teele and
Smith l977; Strauss et al. l98l; Graif et al. l984; Stunden et al. l986; Bowen l988). The
same was implied by Meuwissen and Sloof (l932, l934) and by Jenkinson (l955). While
terminological uncertainties have to be taken into account, it is clear that in all these
instances the "pyloric canal" was equated with the pyloric ring, which was considered to
be the sphincter. Meuwissen and Sloof, for instance, stated that the average length of the
pyloric canal was 1.0 to 2.0 mm in normal infants, which tallies with the width of the
ring. According to these authors the essential factor in the pathogenesis was hypertrophy
and elongation of the pyloric ring or "sphincter".
However, in dissections of morbid anatomical specimens of IHPS, Cunningham (l906)
had shown previously that muscular hypertrophy involved the entire length of the
sphincteric cylinder; it included, but was not limited to, the ring. Forssell (1913) and
Torgersen (l942) showed convincingly that the musculature of the entire canalis
egestorius (the sphincteric cylinder) was involved in the hypertrophy; the findings were
subsequently confirmed by Frimann-Dahl (l935), Runstr"m (l939) and Astley (l952).
Although he did not refer to the anatomical findings of Cunningham (l906), Forssell
(l913) and Torgersen (l942), Heinisch (l967) noted that muscular hypertrophy was not
confined to the pyloric ring but also involved the prepyloric region, which led him to
suggest the term "antrumhypertrophy" for the condition. Analysis of our own cases also
shows that the pyloric sphincteric cylinder in its entirety, is involved.
The premise that the pyloric canal is hypertrophied and elongated in IHPS (where "canal"
is equated with the pyloric ring or sphincter), is difficult to accept. In view of the
evidence quoted it appears much more likely that the entire pyloric sphincteric cylinder is
involved in the hypertrophy, causing a permanently formed pyloric canal with
concomitant motility disturbances. Normally the canal is a fleeting, physiological
structure, being fully formed at the end of a maximal, cyclical contraction of the
sphincteric cylinder (Chap. 13); in IHPS it is permanent, due to muscular hypertrophy of
the entire cylinder.
In their investigations of IHPS many authors (Teele and Smith l977; Strauss et al. l98l;
Blumhagen and Coombs l98l; Blumhagen and Noble l983; Khamapirad and Athey l983;
Graif et al. l984) failed to consider the fundamental anatomical findings of Cunningham
(l906), Forssell (l913) and Torgersen (l942); this may account for much of the
uncertainty surrounding the pathogenesis.
In considering the etiology, it has to be pointed out that numerous theories have been
formulated (some of which will be mentioned or recapitulated briefly). Most authors
agree that the cause remains obscure. Freeman (l929) pointed out that the gizzard in
graminivorous birds was situated in exactly the same location as the pyloric mass in
IHPS. Normally in birds, food is mixed with gastric juice in the proventriculus or
glandular stomach, and ground in the gizzard or muscular stomach. Similarly, in some
higher mammals such as the coloured anteater, the gastric outlet is occupied by a heavy
muscular mass in the same situation as the "tumor" in IHPS. It was thought that the
condition could be of an atavistic nature, a reversion to a more primitive form.
According to Torgersen (l942, 1949) the most likely explanation was a genetic
disturbance associated with excessive asymmetry; this could delay or impede regressive
changes in the circular musculature of the sphincteric cylinder, normally occurring at or
Prolonged pylorospasm was suggested as a possible cause by Meeker and De Nicola
(l948). A genetic defect was also postulated by Carter and Powell (l954) and by Rintoul
and Kirkman (l96l). McKeown and MacMahon (l955) mentioned the possibility of
environmental factors. Belding and Kernohan (l953) demonstrated degeneration of
neurons in the myenteric ganglia of the affected region; Rintoul and Kirkman (l96l) were
unable to substantiate these findings, but postulated an absence of argyrophilic Type I
Dogiel cells from pyloric myenteric ganglia in IHPS.
Friesen et al. (l956) suggested delay in maturation of myenteric ganglion cells; this
statement was questioned by Roberts (l959), as premature infants did not have an
increased incidence of IHPS. Skoryna et al (l959) thought a congenital neuro-muscular
dysfunction of the pyloric sphincteric cylinder could be responsible for both the infantile
and adult forms. Friesen and Pearse (l963) found the ganglion cells in the affected region
to be present in clumps and not arranged in evenly dispersed layers; many cells were
small and immature, suggesting failure or arrest of normal development.
Heinisch (l967) produced hypertrophic pyloric stenosis in rabbits by suturing glass
spheres to the interior of the fornix. Keet and Heydenrych (l97l) found that electrical and
mechanical stimulation of the vagal trunks in the oesophageal hiatus of the diaphragm (in
canines), produced temporary muscular contraction of the pyloric sphincteric cylinder,
indistinguishable from IHPS.
Dodge (l970, l973, l976) as well as Karim et al. (l974) produced IHPS in some newborn
pups by administration of pentagastrin to the mothers (other probands developed
Rogers et al. (l975) and Moazam et al (l978) found no difference in plasma gastrin levels
in infants with and without IHPS, concluding that gastrin stimulation was an unlikely
cause of the muscular hypertrophy.
In view of the fact that the pyloric parasympathetic ganglia and individual muscle cells
appeared normal at electron microscopy, Jona (l978) suggested a "functional" etiology.
Swischuk (l980) thought that prolonged spasm of the "antropyloric muscle" (which could
be due to a variety of causes) was the primary event.
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