The Pyloric Sphincteric Cylinder in Health and Disease



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Chapter 21 (page 98)

Pyloric Membrane, Web or Diaphragm

Pyloric membrane, web or diaphragm has been defined as a thin, circumferential mucosal septum in the pyloric region, projecting intraluminally perpendicular to the long axis of the "antrum". It is composed of two layers of gastric mucosa, with a central core of submucosa and muscularis mucosae; the external muscular and serous coats do not take part in its formation. In the majority of cases a central or eccentric aperture is present, varying from a pinhole to several millimeters in diameter; in a few cases the membrane was unperforated or complete (Rowling l959; Melamed et al. l960; Gerber l965; Parrish et al. l968; Felson et al. l969; Bell et al. l977; Mitchell et al. l979; Jinkins et al. l980).

Pyloric membrane is generally regarded as a congenital anomaly. It is usually associated with symptoms and signs of gastric outlet obstruction. In incomplete membranes symptoms may only occur in adult life, the aperture preventing obstruction for many years (Cremin l969; Jinkins et al. l980). The condition has been described in premature and newborn infants, in older infants and children (Touroff and Sussman l940; Gerber l965; Farman et al. l968; Cremin l969; Bell et al. l977; Fujioka et al. l980; Jinkins et al. l980), and in adults (Farman et al l968; Felson et al l969; Melamed et al l960; Ghent and Denton l974; Ghahremani l974), the ages in adults ranging from 32 to 85 years.

A typical radiographic sign is a radiolucent line 2.0 to 3.0 mm in width, perpendicular to the long axis of the "antrum", representing the membrane (Felson et al. l969). The region between the membrane and the pyloric aperture may be filled with barium, resembling the duodenal bulb; the "double-bulb" appearance is another chracteristic sign (Parrish et al. l968; Felson et al. l969; Bell et al. l977).

In the great majority of cases described in the literature, the membrane was located 1.0 to 4.0 cm proximal to the pyloric aperture; it could perhaps best be designated a "prepyloric" membrane in these cases (vide infra). In a few instances it was very close to, or at the pylorus ("true pyloric membrane"); one case of Rowling (l959), one of Dineen and Redo (l963), one of Gerber (l965), two of Felson et al. (l969) and one of Mitchell (l979) fall into this category. In isolated instances (one case of Felson et al., and one of Ghahremani), a membrane was seen 7.0cm proximal to the pylorus.

In the prepyloric category, the distance of the membrane from the pyloric aperture varied from 1.0 to 2.0 cm in children (Bell et al. l978), and from 1.5 to 4.5 cm in adults (Ghahremani l974). The majority of membranes in adults were located at a distance of 1.5 to 4.0 cm from the pylorus (Rowling l959; Melamed et al. l960; Parrish l968; Cremin l969; Felson et al. l969; Ghahremani l974; Bell et al. l977; Mitchell et al. l979; Jinkins et al. l980).

Discussion

We have not encountered reports in which the prepyloric membrane was described in relation to the pyloric sphincteric cylinder. However, in many descriptions and their accompanying illustrations, it was noted that the prepyloric membrane occurred in the location of the left pyloric loop. This is especially well demonstrated in illustrations accompanying the case report of Rowling (l959), that of Melamed et al (l960), the 3 cases of Parrish et al. (l968), the 2 of Cremin (l969), the one of Ghent and Denton (l974), most of the 10 cases of Bell et al. (l977), the 2 cases of Fujioka et al (l980) and the 4 of Jinkins et al. (l980). It appears to us (but it has not been proved) that, in the majority of cases, the prepyloric mucosal membrane occurs on the luminal aspect of the left pyloric loop of the muscularis externa, in the same way as the mucosal and submucosal parts of the pyloric ring are located on the luminal aspect of the right pyloric loop (to form the pyloric ring). It is interesting to note that Parrish et al. (l968) found a definite thickening in the muscularis externa underlying the membrane in one of their cases; this could conceivably be due to the left loop.

Fujioka et al. (l980) also reported 2 cases of pseudowebs, in whom radiographic examination had shown typical signs of prepyloric membranes; at operation and endoscopy no abnormality was found. In these cases the "webs" were probably caused by prominent, circular mucosal folds. It should be possible to differentiate permanent webs from circular mucosal folds by the characteristic movements and change in position of the folds during contraction of the sphincteric cylinder, as discussed in Chapters 2 and 13. However, a circular mucosal fold may occasionally be permanent, simulating a web (Chap. 28).

References

  1. Bell MJ, Ternberg JL, McAlister W, et al. Antral diaphragm: cause of gastric outlet obstruction in infants and children. J Pediatr l977, 90, 196- 202.
  2. Bell MJ, Ternberg JL, Keating JP, et al. Prepyloric gastric antral web: a puzzling epidemic. J Pediat Surg l978, 13, 307-313.
  3. Cremin BJ. Congenital pyloric antral membranes in infancy. Radiology l969, 92, 509-512.
  4. Dineen JP, Redo SF. Pyloric obstruction due to mucosal diaphragm. Surgery l963, 53, 674-676.
  5. Farman J, Cywes S, Werbeloff L. Pyloric mucosal diaphragms. Clin Rad l968, l9, 95-99.
  6. Felson B, Berkmen YM, Hoyumpa M. Gastric mucosal diaphragm. Radiology l969, 92, 513-517.
  7. Fujioka M, Fisher S, Young LW. Pseudoweb of the gastric antrum in infants. Ped Radiol l980, 9, 73-75.
  8. Gerber BC. Prepyloric diaphragm, an unusual abnormality: a case report. Arch Surg l965, 90, 472-480.
  9. Ghent CN, Denton D. Mucosal diaphragm of the gastric antrum: case report and review of the literature. Canad J Surg l974, 17, 274-278.
  10. Ghahremani GG. Nonobstructive mucosal diaphragms or rings of the gastric antrum in adults. Amer J Roentg Rad Ther Nucl Med l974, 121, 236- 247.
  11. Jinkins JR, Ball TI, Clements JL, et al. Antral mucosal diaphragms in infants and children. Ped Radiol l980, 9, 69-72.
  12. Melamed A, Haukohl RS, Callan E. Pyloric antral mucosal diaphragm with transpyloric mucosal prolapse. Radiology l960, 74, 452-457.
  13. Mitchell KG, McGowan A, Smith DC, et al. Pyloric diaphragm, antral web, congenital antral membrane: a surgical rarity? Brit J Surg l979, 66, 572-574.
  14. Parrish RA, Kanavage CB, Wells JA, et al. Surg Gynaec Obstet l968, 127, 999-1004.
  15. Rowling JT. The prepyloric septum: a rare anomaly. Brit J Surg l959, 47, 162-166.
  16. Touroff ASW, Sussman RM. Congenital prepyloric membranous obstruction in premature infant. Surgery l940, 8, 739-755.


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