The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 24 (page 114)

Keynes (l965) found that 132 cases of simple, primary or idiopathic hypertrophic pyloric stenosis in adults, i.e. muscular hypertrophy without associated lesions, had been described in the English literature up to that time. These included 64 case reports collected from, or added to the literature by North and Johnson (l950), as well as 56 cases reviewed by Christiansen and Grantham (l962) and 2 new cases added by them. Keynes (l965) described the clinical, radiological and pathological findings in 12 new cases of AHPS, 6 of whom had associated peptic ulceration (3 duodenal, 2 gastric and one pyloric), and were designated "complicated" AHPS. The remaining 6 had no associated upper gastro-intestinal lesion and were of the "simple" variety. The gross appearance of the pylorus in diffuse AHPS, both in the simple and the complicated types, was similar to that in IHPS: a smooth, firm or rubbery hard tumor occupied the region of the pylorus, ending abruptly at the duodenum, where it was at its thickest. From here the muscular thickening gradually decreased towards the proximal end of the pyloric canal. Histologically there was hypertrophy of the circular fibres with occasional moderate longitudinal muscular hypertrophy. Keynes (l965) noted no abnormality in the ganglion cells of the myenteric plexuses. The affected region was limited to the pyloric "canal" (pyloric sphincteric cylinder) as described by Cunningham (1906), Horton (1928) and Torgersen (l942). In infants the hypertrophy was always of the simple variety, since it occurred in the absence of other gastro-intestinal pathology, but in adults it could be complicated. Although simple AHPS was uncommon, Keynes (l965) did not believe it was as rare as the literature seemed to suggest.

Du Plessis (l966) described 6 cases of what he termed primary hypertrophic pyloric stenosis commencing in adult life without apparent cause. Gastric resection was performed in 2, both of which showed atrophic gastritis and gastric ulceration. These cases would have been classified secondary AHPS by North and Johnson (1950), and primary AHPS associated with a proximal gastric lesion by Skoryna (l959), Knight (l961) and Christiansen and Grantham (l962). Keynes (l965) would have designated them "complicated" AHPS. Du Plessis (l966) looked upon them as "primary" as he considered the gastric ulceration to be the effect of stasis secondary to the pyloric stenosis. In both resection specimens the circular muscle along the greater curvature showed a marked increase in thickness at the pylorus and for a distance of 2.5 cm proximally. Along the lesser curvature the circular muscle was increased in thickness at the pylorus and up to 1.5 cm proximally. In contrast the longitudinal musculature showed a decrease in thickness over the pylorus and for some distance proximally. The ganglion cells in the myenteric plexuses of the 2 cases appeared normal. In 4 cases there was no associated pathology in the stomach and duodenum. Biopsies taken at the time of operation in all 6 cases showed atrophic gastritis and confirmed the deficiency in the longitudinal musculature.

Interpreting his findings on the anatomical concepts of Torgersen (l942), Du Plessis (l966) suggested that the cause of AHPS was a deficiency of the longitudinal musculature of the pyloric canal (i.e. pyloric sphincteric cylinder), which would result in a failure of the canal to shorten during contraction. This would cause an imbalance of longitudinal and circular muscle contractions resulting in functional obstruction. The circular fibres of the fan-shaped muscle would gradually become hypertrophied as a result of repeated ineffective contractions, adding a mechanical element to the obstruction.

Larson et al. (l967) enumerated the generally accepted radiographic signs as lengthening and narrowing of the pyloric canal with an intact mucosal relief, a contrast filled cleft in the centre of the canal and a crescentic indentation of the duodenal bulb. In 10 cases in whom radiographs showed clear evidence of AHPS, surgical exploration revealed a normal stomach in 5, pyloric carcinoma in 2, AHPS in 1, AHPS and a gastric ulcer in 1, while one case showed evidence of prior surgical treatment for IHPS. It was concluded that there was little direct correlation between the radiographic appearance of pyloric elongation and narrowing on the one hand, and pyloric muscle thickness on the other.

Bodon and Haake (l968) called attention to the frequent association of AHPS with hiatus hernia and reported 11 cases of their own. In these cases the surgical solution was to correct the pyloric hypertrophy by means of pyloroplasty or antrectomy, necessitating an abdominal (as opposed to a transthoracic) approach. At operation the diagnosis of pyloric hypertrophy was not difficult, the hypertrophied muscle presenting as a mass 4.0 to 10 mm thick and 1.0 to 5.0 cm long.

At gastroscopy the hypertrophied muscle resembles the uterine cervix, according to Schuster and Smith (l969). The pyloric opening presents as a hole of fixed diameter in the centre of the mound, thus contrasting with the actively mobile pyloric region of normal subjects. The affected region, unlike the normal "antrum", does not respond to anticholinergics.

Bateson et al. (l969) described l7 cases of AHPS, in 4 of whom there was an associated lesser curvature gastric ulcer, and in one a prepyloric ulcer. None of these cases had associated duodenal ulceration. Macroscopically every case showed hypertrophy of the "pyloric and prepyloric muscle", stopping abruptly at the "pyloric canal" (i.e. pyloric aperture) and thinning out gradually over the adjacent part of the "antrum". Although the hypertrophy was most marked at the pyloroduodenal junction, it also involved the wall of the pyloric "antrum", and a more accurate title according to Bateson et al. (l969) would have been hypertrophic pyloric channel disease, the pyloric channel being defined as the area between the duodenum and a point 2.5 cm proximal to the duodenum. In 5 of the cases it was noted that on touching the pylorus with a gloved finger during operation, the pyloric and adjacent antral muscle contracted, becoming hard and pale. (Comment: a similar appearance was seen during experimental truncal vagal stimulation as described in Chapter 32). This spasm probably accounted as much for the radiological appearances as did the degree and extent of muscle hypertrophy and, in their opinion, made careful measurement of the muscle thickness an academic exercise of doubtful value. Microscopically hypertrophy and hyperplasia of the circular muscle fibres was seen with fibrous tissue between the hypertrophied bundles in every case.

In his review Levin (l97l) came to the conclusion that the radiographic diagnosis of AHPS could not be made with a high degree of confidence. While the signs of hypertrophic pyloric stenosis were diagnostic in infants, this was not always the case in adults. Nevertheless several reports had indicated that AHPS represented persistence of a mild form of IHPS. In his view the poor correlation between the radiographic and pathologic findings led to the conclusion that the elongated, narrowed pylorus was at times due to spasm. In those patients proved to have AHPS, gastric or duodenal ulceration or gastritis had been present in the majority. Indirect evidence suggested that these conditions were the sequelae and not the cause of pyloric muscle hypertrophy. It was important to exclude pyloric carcinoma as a cause of the narrowing in every case.

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