Chapter 13 (page 65)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 13 (page 65)

Types of Closure of the Pyloric Aperture

Radiologically the following types of closure of the aperture may be recognized:

Dynamic closure due to muscular contraction of the sphincteric cylinder

From the above it is concluded that, when the sphincteric cylinder is relaxed or expanded, the aperture is patent. Maximal contraction of the cylinder, with formation of the pyloric canal, closes the aperture.

During contraction of the cylinder there may be an interplay between its right pyloric loop (surrounding the aperture) and its left loop. Should the former close first, retropulsion of contents may occur. Should the left loop close first, propulsion may occur.

Permanent, partial contraction of the sphincteric cylinder (which is regarded as a type of pylorospasm, as described in Chapter 20), may "fix" the aperture in a patent position, midway between maximal patency and maximal closure.
Closure due to converging mucosal folds.

When the pyloric sphincteric cylinder is relaxed, its mucosal folds are circular. The folds may converge on the aperture or close it in an iris-like way.
Descent or sagging of filled stomach.

The pyloric aperture in the filled stomach may be patent (Fig. 13.20). A sudden descent or sagging of the stomach may cause apparent elongation of the aperture with passive narrowing of its diameter (Fig. 13.21).

Gastric hypotonicity with delayed emptying in the erect position, is often ascribed to pylorospasm, by which is meant spasm of the pyloric ring with closure of the aperture. However, there is reason to believe that the aperture is patent in these cases (Chap. 19).

Fig. 13.20. The stomach is filled, the sphincteric cylinder expanded, and the aperture patent

Fig. 13.21. Sagging of stomach causes elongation and apparent narrowing of the aperture